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Operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of around 76.45%. macOS by Apple Inc. is in second place (17.72%), and the varieties of Linux are collectively in third place (1.73%). In the mobile sector (including smartphones and tablets), Android's share is up to 72% in the year 2020. According to third quarter 2016 data, Android's share on smartphones is dominant with 87.5 percent with also a growth rate of 10.3 percent per year, followed by Apple's iOS with 12.1 percent with per year decrease in market share of 5.2 percent, while other operating systems amount to just 0.3 percent. Linux distributions are dominant in the server and supercomputing sectors. Other specialized classes of operating systems (special-purpose operating systems), such as embedded and real-time systems, exist for many applications. Security-focused operating systems also exist. Some operating systems have low system requirements (e.g. light-weight Linux distribution). Others may have higher system requirements. Some operating systems require installation or may come pre-installed with purchased computers (OEM-installation), whereas others may run directly from media (i.e. live CD) or flash memory (i.e. USB stick). Types of operating systems Single-tasking and multi-tasking A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program to be running in concurrency. This is achieved by time-sharing, where the available processor time is divided between multiple processes. These processes are each interrupted repeatedly in time slices by a task-scheduling subsystem of the operating system. Multi-tasking may be characterized in preemptive and co-operative types. In preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, such as Linux—as well as non-Unix-like, such as AmigaOS—support preemptive multitasking. Cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking; 32-bit versions of both Windows NT and Win9x used preemptive multi-tasking. Single- and multi-user Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem. A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, and the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources to multiple users. Distributed A distributed operating system manages a group of distinct, networked computers and makes them appear to be a single computer, as all computations are distributed (divided amongst the constituent computers). Templated In the distributed and cloud computing context of an OS, templating refers to creating a single virtual machine image as a guest operating system, then saving it as a tool for multiple running virtual machines. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses. Embedded Embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines with less autonomy (e.g. PDAs). They are very compact and extremely efficient by design, and are able to operate with a limited amount of resources. Windows CE and Minix 3 are some examples of embedded operating systems. Real-time A real-time operating system is an operating system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. Such an event-driven system switches between tasks based on their priorities or external events, whereas time-sharing operating systems switch tasks based on clock interrupts. Library A library operating system is one in which the services that a typical operating system provides, such as networking, are provided in the form of libraries and composed with the application and configuration code to construct a unikernel: a specialized, single address space, machine image that can be deployed to cloud or embedded environments. History Early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could automatically run different programs in succession to speed up processing. Operating systems did not exist in their modern and more complex forms until the early 1960s. Hardware features were added, that enabled use of runtime libraries, interrupts, and parallel processing. When personal computers became popular in the 1980s, operating systems were made for them similar in concept to those used on larger computers. In the 1940s, the earliest electronic digital systems had no operating systems. Electronic systems of this time were programmed on rows of mechanical switches or by jumper wires on plugboards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the printing of payroll checks from data on punched paper cards. After programmable general-purpose computers were invented, machine languages(consisting of strings of the binary digits 0 and 1 on punched paper tape) were introduced that sped up the programming process (Stern, 1981). In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer for a limited period and would arrive at a scheduled time with their program and data on punched paper cards or punched tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the universal Turing machine. Later machines came with libraries of programs, which would be linked to a user's program to assist in operations such as input and output and compiling (generating machine code from human-readable symbolic code). This was the genesis of the modern-day operating system. However, machines still ran a single job at a time. At Cambridge University in England, the job queue was at one time a washing line (clothesline) from which tapes were hung with different colored clothes-pegs to indicate job priority. An improvement was the Atlas Supervisor. Introduced with the Manchester Atlas in 1962, it is considered by many to be the first recognisable modern operating system. Brinch Hansen described it as "the most significant breakthrough in the history of operating systems." Mainframes Through the 1950s, many major features were pioneered in the field of operating systems on mainframe computers, including batch processing, input/output interrupting, buffering, multitasking, spooling, runtime libraries, link-loading, and programs for sorting records in files. These features were included or not included in application software at the option of application programmers, rather than in a separate operating system used by all applications. In 1959, the SHARE Operating System was released as an integrated utility for the IBM 704, and later in the 709 and 7090 mainframes, although it was quickly supplanted by IBSYS/IBJOB on the 709, 7090 and 7094. During the 1960s, IBM's OS/360 introduced the concept of a single OS spanning an entire product line, which was crucial for the success of the System/360 machines. IBM's current mainframe operating systems are distant descendants of this original system and modern machines are backwards-compatible with applications written for OS/360. OS/360 also pioneered the concept that the operating system keeps track of all of the system resources that are used, including program and data space allocation in main memory and file space in secondary storage, and file locking during updates. When a process is terminated for any reason, all of these resources are re-claimed by the operating system. The alternative CP-67 system for the S/360-67 started a whole line of IBM operating systems focused on the concept of virtual machines. Other operating systems used on IBM S/360 series mainframes included systems developed by IBM: DOS/360 (Disk Operating System), TSS/360 (Time Sharing System), TOS/360 (Tape Operating System), BOS/360 (Basic Operating System), and ACP (Airline Control Program), as well as a few non-IBM systems: MTS (Michigan Terminal System), MUSIC (Multi-User System for Interactive Computing), and ORVYL (Stanford Timesharing System). Control Data Corporation developed the SCOPE operating system in the 1960s, for batch processing. In cooperation with the University of Minnesota, the Kronos and later the NOS operating systems were developed during the 1970s, which supported simultaneous batch and timesharing use. Like many commercial timesharing systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the PLATO operating system, which used plasma panel displays and long-distance time sharing networks. Plato was remarkably innovative for its time, featuring real-time chat, and multi-user graphical games. In 1961, Burroughs Corporation introduced the B5000 with the MCP (Master Control Program) operating system. The B5000 was a stack machine designed to exclusively support high-level languages with no assembler; indeed, the MCP was the first OS to be written exclusively in a high-level language (ESPOL, a dialect of ALGOL). MCP also introduced many other ground-breaking innovations, such as being the first commercial implementation of virtual memory. During development of the AS/400, IBM made an approach to Burroughs to license MCP to run on the AS/400 hardware. This proposal was declined by Burroughs management to protect its existing hardware production. MCP is still in use today in the Unisys company's MCP/ClearPath line of computers. UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this batch-oriented system managed magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BC system. General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed General Comprehensive Operating System (GCOS). Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Before the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community. RT-11 was a single-user real-time OS for the PDP-11 class minicomputer, and RSX-11 was the corresponding multi-user OS. From the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in order to permit different underlying computer architectures to appear to be the same as others in a series. In fact, most 360s after the 360/40 (except the 360/44, 360/75, 360/91, 360/95 and 360/195) were microprogrammed implementations. The enormous investment in software for these systems made since the 1960s caused most of the original computer manufacturers to continue to develop compatible operating systems along with the hardware. Notable supported mainframe operating systems include: Burroughs MCP B5000, 1961 to Unisys Clearpath/MCP, present IBM OS/360 IBM System/360, 1966 to IBM z/OS, present IBM CP-67 IBM System/360, 1967 to IBM z/VM UNIVAC EXEC 8 UNIVAC 1108, 1967, to OS 2200 Unisys Clearpath Dorado, present Microcomputers The first microcomputers did not have the capacity or need for the elaborate operating systems that had been developed for mainframes and minis; minimalistic operating systems were developed, often loaded from ROM and known as monitors. One notable early disk operating system was CP/M, which was supported on many early microcomputers and was closely imitated by Microsoft's MS-DOS, which became widely popular as the operating system chosen for the IBM PC (IBM's version of it was called IBM DOS or PC DOS). In the 1980s, Apple Computer Inc. (now Apple Inc.) abandoned its popular Apple II series of microcomputers to introduce the Apple Macintosh computer with an innovative graphical user interface (GUI) to the Mac OS. The introduction of the Intel 80386 CPU chip in October 1985, with 32-bit architecture and paging capabilities, provided personal computers with the ability to run multitasking operating systems like those of earlier minicomputers and mainframes. Microsoft responded to this progress by hiring Dave Cutler, who had developed the VMS operating system for Digital Equipment Corporation. He would lead the development of the Windows NT operating system, which continues to serve as the basis for Microsoft's operating systems line. Steve Jobs, a co-founder of Apple Inc., started NeXT Computer Inc., which developed the NEXTSTEP operating system. NEXTSTEP would later be acquired by Apple Inc. and used, along with code from FreeBSD as the core of Mac OS X (macOS after latest name change). The GNU Project was started by activist and programmer Richard Stallman with the goal of creating a complete free software replacement to the proprietary UNIX operating system. While the project was highly successful in duplicating the functionality of various parts of UNIX, development of the GNU Hurd kernel proved to be unproductive. In 1991, Finnish computer science student Linus Torvalds, with cooperation from volunteers collaborating over the Internet, released the first version of the Linux kernel. It was soon merged with the GNU user space components and system software to form a complete operating system. Since then, the combination of the two major components has usually been referred to as simply "Linux" by the software industry, a naming convention that Stallman and the Free Software Foundation remain opposed to, preferring the name GNU/Linux. The Berkeley Software Distribution, known as BSD, is the UNIX derivative distributed by the University of California, Berkeley, starting in the 1970s. Freely distributed and ported to many minicomputers, it eventually also gained a following for use on PCs, mainly as FreeBSD, NetBSD and OpenBSD. Examples Unix and Unix-like operating systems Unix was originally written in assembly language. Ken Thompson wrote B, mainly based on BCPL, based on his experience in the MULTICS project. B was replaced by C, and Unix, rewritten in C, developed into a large, complex family of inter-related operating systems which have been influential in every modern operating system (see History). The Unix-like family is a diverse group of operating systems, with several major sub-categories including System V, BSD, and Linux. The name "UNIX" is a trademark of The Open Group which licenses it for use with any operating system that has been shown to conform to their definitions. "UNIX-like" is commonly used to refer to the large set of operating systems which resemble the original UNIX. Unix-like systems run on a wide variety of computer architectures. They are used heavily for servers in business, as well as workstations in academic and engineering environments. Free UNIX variants, such as Linux and BSD, are popular in these areas. Five operating systems are certified by The Open Group (holder of the Unix trademark) as Unix. HP's HP-UX and IBM's AIX are both descendants of the original System V Unix and are designed to run only on their respective vendor's hardware. In contrast, Sun Microsystems's Solaris can run on multiple types of hardware, including x86 and Sparc servers, and PCs. Apple's macOS, a replacement for Apple's earlier (non-Unix) Mac OS, is a hybrid kernel-based BSD variant derived from NeXTSTEP, Mach, and FreeBSD. IBM's z/OS UNIX System Services includes a shell and utilities based on Mortice Kerns' InterOpen products. Unix interoperability was sought by establishing the POSIX standard. The POSIX standard can be applied to any operating system, although it was originally created for various Unix variants. BSD and its descendants A subgroup of the Unix family is the Berkeley Software Distribution family, which includes FreeBSD, NetBSD, and OpenBSD. These operating systems are most commonly found on webservers, although they can also function as a personal computer OS. The Internet owes much of its existence to BSD, as many of the protocols now commonly used by computers to connect, send and receive data over a network were widely implemented and refined in BSD. The World Wide Web was also first demonstrated on a number of computers running an OS based on BSD called NeXTSTEP. In 1974, University of California, Berkeley installed its first Unix system. Over time, students and staff in the computer science department there began adding new programs to make things easier, such as text editors. When Berkeley received new VAX computers in 1978 with Unix installed, the school's undergraduates modified Unix even more in order to take advantage of the computer's hardware possibilities. The Defense Advanced Research Projects Agency of the US Department of Defense took interest, and decided to fund the project. Many schools, corporations, and government organizations took notice and started to use Berkeley's version of Unix instead of the official one distributed by AT&T. Steve Jobs, upon leaving Apple Inc. in 1985, formed NeXT Inc., a company that manufactured high-end computers running on a variation of BSD called NeXTSTEP. One of these computers was used by Tim Berners-Lee as the first webserver to create the World Wide Web. Developers like Keith Bostic encouraged the project to replace any non-free code that originated with Bell Labs. Once this was done, however, AT&T sued. After two years of legal disputes, the BSD project spawned a number of free derivatives, such as NetBSD and FreeBSD (both in 1993), and OpenBSD (from NetBSD in 1995). macOS macOS (formerly "Mac OS X" and later "OS X") is a line of open core graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers. macOS is the successor to the original classic Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessor, macOS is a UNIX operating system built on technology that had been developed at NeXT through the second half of the 1980s and up until Apple purchased the company in early 1997. The operating system was first released in 1999 as Mac OS X Server 1.0, followed in March 2001 by a client version (Mac OS X v10.0 "Cheetah"). Since then, six more distinct "client" and "server" editions of macOS have been released, until the two were merged in OS X 10.7 "Lion". Prior to its merging with macOS, the server edition macOS Server was architecturally identical to its desktop counterpart and usually ran on Apple's line of Macintosh server hardware. macOS Server included work group management and administration software tools that provide simplified access to key network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and others. With Mac OS X v10.7 Lion, all server aspects of Mac OS X Server have been integrated into the client version and the product re-branded as "OS X" (dropping "Mac" from the name). The server tools are now offered as an application. z/OS UNIX System Services First introduced as the OpenEdition upgrade to MVS/ESA System Product Version 4 Release 3, announced February 1993 with support for POSIX and other standards., z/OS UNIX System Services is built on top of MVS services and cannot run independently. While IBM initially introduced OpenEdition to satisfy FIPS requirements, several z/OS component now require UNIX services, e.g., TCP/IP. Linux The Linux kernel originated in 1991, as a project of Linus Torvalds, while a university student in Finland. He posted information about his project on a newsgroup for computer students and programmers, and received support and assistance from volunteers who succeeded in creating a complete and functional kernel. Linux is Unix-like, but was developed without any Unix code, unlike BSD and its variants. Because of its open license model, the Linux kernel code is available for study and modification, which resulted in its use on a wide range of computing machinery from supercomputers to smart-watches. Although estimates suggest that Linux is used on only 1.82% of all "desktop" (or laptop) PCs, it has been widely adopted for use in servers and embedded systems such as cell phones. Linux has superseded Unix on many platforms and is used on most supercomputers including the top 385. Many of the same computers are also on Green500 (but in different order), and Linux runs on the top 10. Linux is also commonly used on other small energy-efficient computers, such as smartphones and smartwatches. The Linux kernel is used in some popular distributions, such as Red Hat, Debian, Ubuntu, Linux Mint and Google's Android, Chrome OS, and Chromium OS. Microsoft Windows Microsoft Windows is a family of proprietary operating systems designed by Microsoft Corporation and primarily targeted to Intel architecture based computers, with an estimated 88.9 percent total usage share on Web connected computers. The latest version is Windows 11. In 2011, Windows 7 overtook Windows XP as most common version in use. Microsoft Windows was first released in 1985, as an operating environment running on top of MS-DOS, which was the standard operating system shipped on most Intel architecture personal computers at the time. In 1995, Windows 95 was released which only used MS-DOS as a bootstrap. For backwards compatibility, Win9x could run real-mode MS-DOS and 16-bit Windows 3.x drivers. Windows ME, released in 2000, was the last version in the Win9x family. Later versions have all been based on the Windows NT kernel. Current client versions of Windows run on IA-32, x86-64 and ARM microprocessors. In addition Itanium is still supported in older server version Windows Server 2008 R2. In the past, Windows NT supported additional architectures. Server editions of Windows are widely used. In recent years, Microsoft has expended significant capital in an effort to promote the use of Windows as a server operating system. However, Windows' usage on servers is not as widespread as on personal computers as Windows competes against Linux and BSD for server market share. ReactOS is a Windows-alternative operating system, which is being developed on the principles of Windows without using any of Microsoft's code. Other There have been many operating systems that were significant in their day but are no longer so, such as AmigaOS; OS/2 from IBM and Microsoft; classic Mac OS, the non-Unix precursor to Apple's macOS; BeOS; XTS-300; RISC OS; MorphOS; Haiku; BareMetal and FreeMint. Some are still used in niche markets and continue to be developed as minority platforms for enthusiast communities and specialist applications. OpenVMS, formerly from DEC, is still under active development by VMS Software Inc. Yet other operating systems are used almost exclusively in academia, for operating systems education or to do research on operating system concepts. A typical example of a system that fulfills both roles is MINIX, while for example Singularity is used purely for research. Another example is the Oberon System designed at ETH Zürich by Niklaus Wirth, Jürg Gutknecht and a group of students at the former Computer Systems Institute in the 1980s. It was used mainly for research, teaching, and daily work in Wirth's group. Other operating systems have failed to win significant market share, but have introduced innovations that have influenced mainstream operating systems, not least Bell Labs' Plan 9. Components The components of an operating system all exist in order to make the different parts of a computer work together. All user software needs to go through the operating system in order to use any of the hardware, whether it be as simple as a mouse or keyboard or as complex as an Internet component. Kernel With the aid of the firmware and device drivers, the kernel provides the most basic level of control over all of the computer's hardware devices. It manages memory access for programs in the RAM, it determines which programs get access to which hardware resources, it sets up or resets the CPU's operating states for optimal operation at all times, and it organizes the data for long-term non-volatile storage with file systems on such media as disks, tapes, flash memory, etc. Program execution The operating system provides an interface between an application program and the computer hardware, so that an application program can interact with the hardware only by obeying rules and procedures programmed into the operating system. The operating system is also a set of services which simplify development and execution of application programs. Executing an application program involves the creation of a process by the operating system kernel which assigns memory space and other resources, establishes a priority for the process in multi-tasking systems, loads program binary code into memory, and initiates execution of the application program which then interacts with the user and with hardware devices. Interrupts Interrupts are central to most operating systems, as they provide an efficient way to react to the environment. Interrupts cause the central processing unit (CPU) to have a control flow change away from the currently running process. Input/Output (I/O) devices are slower than the CPU's clock signal. Therefore, it would slow down the computer if the CPU had to wait for each I/O to finish. Instead, a computer may implement direct memory access (DMA) I/O. The details of how a computer processes an interrupt vary from architecture to architecture, and the details of how interrupt service routines behave from operating system to operating system. The scenario below is typical, although the details for some other hardware and operating systems vary significantly. If a computer program in a computer with a direct memory access chip executes a system call to perform a DMA I/O blocking write operation, then the system call might execute the following instructions: Set the contents of the CPU's registers (including the program counter) into the process control block. Create an entry in the device-status table. The operating system maintains this table to keep track of which processes are waiting for which devices. One field in the table is the memory address of the process control block. Place all the characters to be sent to the device into a memory buffer. Set the memory address of the memory buffer to a predetermined device register. Set the buffer size (an integer) to another predetermined register. Execute the machine instruction to begin the writing. Perform a context switch to the next process in the ready queue. While the writing takes place, the operating system will context switch to other processes as normal. When the device finishes writing, the device will interrupt the currently running process by asserting an interrupt request. The device will also place an integer onto the device's data bus. Upon accepting the interrupt request, the CPU will: Push the contents of its program counter and program status word onto the call stack. Read the integer from the data bus. The integer is an offset to the interrupt vector table. The vector table's instructions will return control to the operating system. The operating system will then: Access the device-status table. Extract the process control block. Perform a context switch back to the writing process. When the writing process has its time slice expired, the CPU will: Pop from the call stack the program status word and set it back to its register. Pop from the call stack the address of the interrupted process' next instruction and set it back into the program counter. The interrupted process will then resume its time slice. Modes Modern computers support multiple modes of operation. CPUs with this capability offer at least two modes: user mode and supervisor mode. In general terms, supervisor mode operation allows unrestricted access to all machine resources, including all MPU instructions. User mode operation sets limits on instruction use and typically disallows direct access to machine resources. CPUs might have other modes similar to user mode as well, such as the virtual modes in order to emulate older processor types, such as 16-bit processors on a 32-bit one, or 32-bit processors on a 64-bit one. At power-on or reset, the system begins in supervisor mode. Once an operating system kernel has been loaded and started, the boundary between user mode and supervisor mode (also known as kernel mode) can be established. Supervisor mode is used by the kernel for low level tasks that need unrestricted access to hardware, such as controlling how memory is accessed, and communicating with devices such as disk drives and video display devices. User mode, in contrast, is used for almost everything else. Application programs, such as word processors and database managers, operate within user mode, and can only access machine resources by turning control over to the kernel, a process which causes a switch to supervisor mode. Typically, the transfer of control to the kernel is achieved by executing a software interrupt instruction, such as the Motorola 68000 TRAP instruction. The software interrupt causes the processor to switch from user mode to supervisor mode and begin executing code that allows the kernel to take control. In user mode, programs usually have access to a restricted set of processor instructions, and generally cannot execute any instructions that could potentially cause disruption to the system's operation. In supervisor mode, instruction execution restrictions are typically removed, allowing the kernel unrestricted access to all machine resources. The term "user mode resource" generally refers to one or more CPU registers, which contain information that the running program isn't allowed to alter. Attempts to alter these resources generally causes a switch to supervisor mode, where the operating system can deal with the illegal operation the program was attempting, for example, by forcibly terminating ("killing") the program. Memory management Among other things, a multiprogramming operating system kernel must be responsible for managing all system memory which is currently in use by programs. This ensures that a program does not interfere with memory already in use by another program. Since programs time share, each program must have independent access to memory. Cooperative memory management, used by many early operating systems, assumes that all programs make voluntary use of the kernel's memory manager, and do not exceed their allocated memory. This system of memory management is almost never seen any more, since programs often contain bugs which can cause them to exceed their allocated memory. If a program fails, it may cause memory used by one or more other programs to be affected or overwritten. Malicious programs or viruses may purposefully alter another program's memory, or may affect the operation of the operating system itself. With cooperative memory management, it takes only one misbehaved program to crash the system. Memory protection enables the kernel to limit a process' access to the computer's memory. Various methods of memory protection exist, including memory segmentation and paging. All methods require some level of hardware support (such as the 80286 MMU), which doesn't exist in all computers. In both segmentation and paging, certain protected mode registers specify to the CPU what memory address it should allow a running program to access. Attempts to access other addresses trigger an interrupt which cause the CPU to re-enter supervisor mode, placing the kernel in charge. This is called a segmentation violation or Seg-V for short, and since it is both difficult to assign a meaningful result to such an operation, and because it is usually a sign of a misbehaving program, the kernel generally resorts to terminating the offending program, and reports the error. Windows versions 3.1 through ME had some level of memory protection, but programs could easily circumvent the need to use it. A general protection fault would be produced, indicating a segmentation violation had occurred; however, the system would often crash anyway. Virtual memory The use of virtual memory addressing (such as paging or segmentation) means that the kernel can choose what memory each program may use at any given time, allowing the operating system to use the same memory locations for multiple tasks. If a program tries to access memory that isn't in its current range of accessible memory, but nonetheless has been allocated to it, the kernel is interrupted in the same way as it would if the program were to exceed its allocated memory. (See section on memory management.) Under UNIX this kind of interrupt is referred to as a page fault. When the kernel detects a page fault it generally adjusts the virtual memory range of the program which triggered it, granting it access to the memory requested. This gives the kernel discretionary power over where a particular application's memory is stored, or even whether or not it has actually been allocated yet. In modern operating systems, memory which is accessed less frequently can be temporarily stored on disk or other media to make that space available for use by other programs. This is called swapping, as an area of memory can be used by multiple programs, and what that memory area contains can be swapped or exchanged on demand. "Virtual memory" provides the programmer or the user with the perception that there is a much larger amount of RAM in the computer than is really there. Multitasking Multitasking refers to the running of multiple independent computer programs on the same computer; giving the appearance that it is performing the tasks at the same time. Since most computers can do at most one or two things at one time, this is generally done via time-sharing, which means that each program uses a share of the computer's time to execute. An operating system kernel contains a scheduling program which determines how much time each process spends executing, and in which order execution control should be passed to programs. Control is passed to a process by the kernel, which allows the program access to the CPU and memory. Later, control is returned to the kernel through some mechanism, so that another program may be allowed to use the CPU. This so-called passing of control between the kernel and applications is called a context switch. An early model which governed the allocation of time to programs was called cooperative multitasking. In this model, when control is passed to a program by the kernel, it may execute for as long as it wants before explicitly returning control to the kernel. This means that a malicious or malfunctioning program may not only prevent any other programs from using the CPU, but it can hang the entire system if it enters an infinite loop. Modern operating systems extend the concepts of application preemption to device drivers and kernel code, so that the operating system has preemptive control over internal run-times as well. The philosophy governing preemptive multitasking is that of ensuring that all programs are given regular time on the CPU. This implies that all programs must be limited in how much time they are allowed to spend on the CPU without being interrupted. To accomplish this, modern operating system kernels make use of a timed interrupt. A protected mode timer is set by the kernel which triggers a return to supervisor mode after the specified time has elapsed. (See above sections on Interrupts and Dual Mode Operation.) On many single user operating systems cooperative multitasking is perfectly adequate, as home computers generally run a small number of well tested programs. The AmigaOS is an exception, having preemptive multitasking from its first version. Windows NT was the first version of Microsoft Windows which enforced preemptive multitasking, but it didn't reach the home user market until Windows XP (since Windows NT was targeted at professionals). Disk access and file systems Access to data stored on disks is a central feature of all operating systems. Computers store data on disks using files, which are structured in specific ways in order to allow for faster access, higher reliability, and to make better use of the drive's available space. The specific way in which files are stored on a disk is called a file system, and enables files to have names and attributes. It also allows them to be stored in a hierarchy of directories or folders arranged in a directory tree. Early operating systems generally supported a single type of disk drive and only one kind of file system. Early file systems were limited in their capacity, speed, and in the kinds of file names and directory structures they could use. These limitations often reflected limitations in the operating systems they were designed for, making it very difficult for an operating system to support more than one file system. While many simpler operating systems support a limited range of options for accessing storage systems, operating systems like UNIX and Linux support a technology known as a virtual file system or VFS. An operating system such as UNIX supports a wide array of storage devices, regardless of their design or file systems, allowing them to be accessed through a common application programming interface (API). This makes it unnecessary for programs to have any knowledge about the device they are accessing. A VFS allows the operating system to provide programs with access to an unlimited number of devices with an infinite variety of file systems installed on them, through the use of specific device drivers and file system drivers. A connected storage device, such as a hard drive, is accessed through a device driver. The device driver understands the specific language of the drive and is able to translate that language into a standard language used by the operating system to access all disk drives. On UNIX, this is the language of block devices. When the kernel has an appropriate device driver in place, it can then access the contents of the disk drive in raw format, which may contain one or more file systems. A file system driver is used to translate the commands used to access each specific file system into a standard set of commands that the operating system can use to talk to all file systems. Programs can then deal with these file systems on the basis of filenames, and directories/folders, contained within a hierarchical structure. They can create, delete, open, and close files, as well as gather various information about them, including access permissions, size, free space, and creation and modification dates. Various differences between file systems make supporting all file systems difficult. Allowed characters in file names, case sensitivity, and the presence of various kinds of file attributes makes the implementation of a single interface for every file system a daunting task. Operating systems tend to recommend using (and so support natively) file systems specifically designed for them; for example, NTFS in Windows and ReiserFS, Reiser4, ext3, ext4 and Btrfs in Linux. However, in practice, third party drivers are usually available to give support for the most widely used file systems in most general-purpose operating systems (for example, NTFS is available in Linux through NTFS-3g, and ext2/3 and ReiserFS are available in Windows through third-party software). Support for file systems is highly varied among modern operating systems, although there are several common file systems which almost all operating systems include support and drivers for. Operating systems vary on file system support and on the disk formats they may be installed on. Under Windows, each file system is usually limited in application to certain media; for example, CDs must use ISO 9660 or UDF, and as of Windows Vista, NTFS is the only file system which the operating system can be installed on. It is possible to install Linux onto many types of file systems. Unlike other operating systems, Linux and UNIX allow any file system to be used regardless of the media it is stored in, whether it is a hard drive, a disc (CD, DVD...), a USB flash drive, or even contained within a file located on another file system. Device drivers A device driver is a specific type of computer software developed to allow interaction with hardware devices. Typically this constitutes an interface for communicating with the device, through the specific computer bus or communications subsystem that the hardware is connected to, providing commands to and/or receiving data from the device, and on the other end, the requisite interfaces to the operating system and software applications. It is a specialized hardware-dependent computer program which is also operating system specific that enables another program, typically an operating system or applications software package or computer program running under the operating system kernel, to interact transparently with a hardware device, and usually provides the requisite interrupt handling necessary for any necessary asynchronous time-dependent hardware interfacing needs. The key design goal of device drivers is abstraction. Every model of hardware (even within the same class of device) is different. Newer models also are released by manufacturers that provide more reliable or better performance and these newer models are often controlled differently. Computers and their operating systems cannot be expected to know how to control every device, both now and in the future. To solve this problem, operating systems essentially dictate how every type of device should be controlled. The function of the device driver is then to translate these operating system mandated function calls into device specific calls. In theory a new device, which is controlled in a new manner, should function correctly if a suitable driver is available. This new driver ensures that the device appears to operate as usual from the operating system's point of view. Under versions of Windows before Vista and versions of Linux before 2.6, all driver execution was co-operative, meaning that if a driver entered an infinite loop it would freeze the system. More recent revisions of these operating systems incorporate kernel preemption, where the kernel interrupts the driver to give it tasks, and then separates itself from the process until it receives a response from the device driver, or gives it more tasks to do. Networking Currently most operating systems support a variety of networking protocols, hardware, and applications for using them. This means that computers running dissimilar operating systems can participate in a common network for sharing resources such as computing, files, printers, and scanners using either wired or wireless connections. Networks can essentially allow a computer's operating system to access the resources of a remote computer to support the same functions as it could if those resources were connected directly to the local computer. This includes everything from simple communication, to using networked file systems or even sharing another computer's graphics or sound hardware. Some network services allow the resources of a computer to be accessed transparently, such as SSH which allows networked users direct access to a computer's command line interface. Client/server networking allows a program on a computer, called a client, to connect via a network to another computer, called a server. Servers offer (or host) various services to other network computers and users. These services are usually provided through ports or numbered access points beyond the server's IP address. Each port number is usually associated with a maximum of one running program, which is responsible for handling requests to that port. A daemon, being a user program, can in turn access the local hardware resources of that computer by passing requests to the operating system kernel. Many operating systems support one or more vendor-specific or open networking protocols as well, for example, SNA on IBM systems, DECnet on systems from Digital Equipment Corporation, and Microsoft-specific protocols (SMB) on Windows. Specific protocols for specific tasks may also be supported such as NFS for file access. Protocols like ESound, or esd can be easily extended over the network to provide sound from local applications, on a remote system's sound hardware. Security A computer being secure depends on a number of technologies working properly. A modern operating system provides access to a number of resources, which are available to software running on the system, and to external devices like networks via the kernel. The operating system must be capable of distinguishing between requests which should be allowed to be processed, and others which should not be processed. While some systems may simply distinguish between "privileged" and "non-privileged", systems commonly have a form of requester identity, such as a user name. To establish identity there may be a process of authentication. Often a username must be quoted, and each username may have a password. Other methods of authentication, such as magnetic cards or biometric data, might be used instead. In some cases, especially connections from the network, resources may be accessed with no authentication at all (such as reading files over a network share). Also covered by the concept of requester identity is authorization; the particular services and resources accessible by the requester once logged into a system are tied to either the requester's user account or to the variously configured groups of users to which the requester belongs. In addition to the allow or disallow model of security, a system with a high level of security also offers auditing options. These would allow tracking of requests for access to resources (such as, "who has been reading this file?"). Internal security, or security from an already running program is only possible if all possibly harmful requests must be carried out through interrupts to the operating system kernel. If programs can directly access hardware and resources, they cannot be secured. External security involves a request from outside the computer, such as a login at a connected console or some kind of network connection. External requests are often passed through device drivers to the operating system's kernel, where they can be passed onto applications, or carried out directly. Security of operating systems has long been a concern because of highly sensitive data held on computers, both of a commercial and military nature. The United States Government Department of Defense (DoD) created the Trusted Computer System Evaluation Criteria (TCSEC) which is a standard that sets basic requirements for assessing the effectiveness of security. This became of vital importance to operating system makers, because the TCSEC was used to evaluate, classify and select trusted operating systems being considered for the processing, storage and retrieval of sensitive or classified information. Network services include offerings such as file sharing, print services, email, web sites, and file transfer protocols (FTP), most of which can have compromised security. At the front line of security are hardware devices known as firewalls or intrusion detection/prevention systems. At the operating system level, there are a number of software firewalls available, as well as intrusion detection/prevention systems. Most modern operating systems include a software firewall, which is enabled by default. A software firewall can be configured to allow or deny network traffic to or from a service or application running on the operating system. Therefore, one can install and be running an insecure service, such as Telnet or FTP, and not have to be threatened by a security breach because the firewall would deny all traffic trying to connect to the service on that port. An alternative strategy, and the only sandbox strategy available in systems that do not meet the Popek and Goldberg virtualization requirements, is where the operating system is not running user programs as native code, but instead either emulates a processor or provides a host for a p-code based system such as Java. Internal security is especially relevant for multi-user systems; it allows each user of the system to have private files that the other users cannot tamper with or read. Internal security is also vital if auditing is to be of any use, since a program can potentially bypass the operating system, inclusive of bypassing auditing. User interface Every computer that is to be operated by an individual requires a user interface. The user interface is usually referred to as a shell and is essential if human interaction is to be supported. The user interface views the directory structure and requests services from the operating system that will acquire data from input hardware devices, such as a keyboard, mouse or credit card reader, and requests operating system services to display prompts, status messages and such on output hardware devices, such as a video monitor or printer. The two most common forms of a user interface have historically been the command-line interface, where computer commands are typed out line-by-line, and the graphical user interface, where a visual environment (most commonly a WIMP) is present. Graphical user interfaces Most of the modern computer systems support graphical user interfaces (GUI), and often include them. In some computer systems, such as the original implementation of the classic Mac OS, the GUI is integrated into the kernel. While technically a graphical user interface is not an operating system service, incorporating support for one into the operating system kernel can allow the GUI to be more responsive by reducing the number of context switches required for the GUI to perform its output functions. Other operating systems are modular, separating the graphics subsystem from the kernel and the Operating System. In the 1980s UNIX, VMS and many others had operating systems that were built this way. Linux and macOS are also built this way. Modern releases of Microsoft Windows such as Windows Vista implement a graphics subsystem that is mostly in user-space; however the graphics drawing routines of versions between Windows NT 4.0 and Windows Server 2003 exist mostly in kernel space. Windows 9x had very little distinction between the interface and the kernel. Many computer operating systems allow the user to install or create any user interface they desire. The X Window System in conjunction with GNOME or KDE Plasma 5 is a commonly found setup on most Unix and Unix-like (BSD, Linux, Solaris) systems. A number of Windows shell replacements have been released for Microsoft Windows, which offer alternatives to the included Windows shell, but the shell itself cannot be separated from Windows. Numerous Unix-based GUIs have existed over time, most derived from X11. Competition among the various vendors of Unix (HP, IBM, Sun) led to much fragmentation, though an effort to standardize in the 1990s to COSE and CDE failed for various reasons, and were eventually eclipsed by the widespread adoption of GNOME and K Desktop Environment. Prior to free software-based toolkits and desktop environments, Motif was the prevalent toolkit/desktop combination (and was the basis upon which CDE was developed). Graphical user interfaces evolve over time. For example, Windows has modified its user interface almost every time a new major version of Windows is released, and the Mac OS GUI changed dramatically with the introduction of Mac OS X in 1999. Real-time operating systems A real-time operating system (RTOS) is an operating system intended for applications with fixed deadlines (real-time computing). Such applications include some small embedded systems, automobile engine controllers, industrial robots, spacecraft, industrial control, and some large-scale computing systems. An early example of a large-scale real-time operating system was Transaction Processing Facility developed by American Airlines and IBM for the Sabre Airline Reservations System. Embedded systems that have fixed deadlines use a real-time operating system such as VxWorks, PikeOS, eCos, QNX, MontaVista Linux and RTLinux. Windows CE is a real-time operating system that shares similar APIs to desktop Windows but shares none of desktop Windows' codebase. Symbian OS also has an RTOS kernel (EKA2) starting with version 8.0b. Some embedded systems use operating systems such as Palm OS, BSD, and Linux, although such operating systems do not support real-time computing. Operating system development as a hobby A hobby operating system may be classified as one whose code has not been directly derived from an existing operating system, and has few users and active developers. In some cases, hobby development is in support of a "homebrew" computing device, for example, a simple single-board computer powered by a 6502 microprocessor. Or, development may be for an architecture already in widespread use. Operating system development may come from entirely new concepts, or may commence by modeling an existing operating system. In either case, the hobbyist is his/her own developer, or may interact with a small and sometimes unstructured group of individuals who have like interests. Examples of a hobby operating system include Syllable and TempleOS. Diversity of operating systems and portability Application software is generally written for use on a specific operating system, and sometimes even for specific hardware. When porting the application to run on another OS, the functionality required by that application may be implemented differently by that OS (the names of functions, meaning of arguments, etc.) requiring the application to be adapted, changed, or otherwise maintained. Unix was the first operating system not written in assembly language, making it very portable to systems different from its native PDP-11. This cost in supporting operating systems diversity can be avoided by instead writing applications against software platforms such as Java or Qt. These abstractions have already borne the cost of adaptation to specific operating systems and their system libraries. Another approach is for operating system vendors to adopt standards. For example, POSIX and OS abstraction layers provide commonalities that reduce porting costs. Market share See also Comparison of operating systems Crash (computing) Hypervisor Interruptible operating system List of important publications in operating systems List of operating systems List of pioneers in computer science Live CD Glossary of operating systems terms Microcontroller Mobile device Mobile operating system Network operating system Object-oriented operating system Operating System Projects System Commander System image Timeline of operating systems Notes References Further reading O'Brien, J. A., & Marakas, G. M.(2011). Management Information Systems. 10e. McGraw-Hill Irwin. External links Multics History and the history of operating systems

Operating System (OS)

List of operating systems This is a list of operating systems. Computer operating systems can be categorized by technology, ownership, licensing, working state, usage, and by many other characteristics. In practice, many of these groupings may overlap. Criteria for inclusion is notability, as shown either through an existing Wikipedia article or citation to a reliable source. Proprietary Acorn Computers Arthur ARX MOS RISC iX RISC OS Amazon Fire OS Amiga Inc. AmigaOS AmigaOS 1.0-3.9 (Motorola 68000) AmigaOS 4 (PowerPC) Amiga Unix (a.k.a. Amix) Amstrad AMSDOS Contiki CP/M 2.2 CP/M Plus SymbOS Apple Inc. Apple II family Apple DOS Apple Pascal ProDOS GS/OS GNO/ME Contiki Apple III Apple SOS Apple Lisa Apple Macintosh Classic Mac OS A/UX (UNIX System V with BSD extensions) Copland MkLinux Pink Rhapsody macOS (formerly Mac OS X and OS X) macOS Server (formerly Mac OS X Server and OS X Server) Apple Network Server IBM AIX (Apple-customized) Apple MessagePad Newton OS iPhone and iPod Touch iOS (formerly iPhone OS) iPad iPadOS Apple Watch watchOS Apple TV tvOS Embedded operating systems A/ROSE bridgeOS iPod software (unnamed embedded OS for iPod) Unnamed NetBSD variant for Airport Extreme and Time Capsule Apollo Computer, Hewlett-Packard Domain/OS – One of the first network-based systems. Run on Apollo/Domain hardware. Later bought by Hewlett-Packard. Atari Atari DOS (for 8-bit computers) Atari TOS Atari MultiTOS Contiki (for 8-bit, ST, Portfolio) BAE Systems XTS-400 Be Inc. BeOS BeIA BeOS r5.1d0 magnussoft ZETA (based on BeOS r5.1d0 source code, developed by yellowTAB) Bell Labs Unix ("Ken's new system," for its creator (Ken Thompson), officially Unics and then Unix, the prototypic operating system created in Bell Labs in 1969 that formed the basis for the Unix family of operating systems) UNIX Time-Sharing System v1 UNIX Time-Sharing System v2 UNIX Time-Sharing System v3 UNIX Time-Sharing System v4 UNIX Time-Sharing System v5 UNIX Time-Sharing System v6 MINI-UNIX PWB/UNIX USG CB Unix UNIX Time-Sharing System v7 (It is from Version 7 Unix (and, to an extent, its descendants listed below) that almost all Unix-based and Unix-like operating systems descend.) Unix System III Unix System IV Unix System V Unix System V Releases 2.0, 3.0, 3.2, 4.0, and 4.2 UNIX Time-Sharing System v8 UNIX Time-Sharing System v9 UNIX Time-Sharing System v10 Non-Unix Operating Systems: BESYS Plan 9 from Bell Labs Inferno Burroughs Corporation, Unisys Burroughs MCP Commodore International GEOS AmigaOS AROS Research Operating System Control Data Corporation Lower 3000 series SCOPE (Supervisory Control Of Program Execution) Upper 3000 series SCOPE (Supervisory Control Of Program Execution) Drum SCOPE 6x00 and related Cyber Chippewa Operating System (COS) MACE (Mansfield and Cahlander Executive) Kronos (Kronographic OS) NOS (Network Operating System) NOS/VE NOS Virtual Environment SCOPE (Supervisory Control Of Program Execution) NOS/BE NOS Batch Environment SIPROS (Simultaneous Processing Operating System) CloudMosa Puffin OS Convergent Technologies Convergent Technologies Operating System – later acquired by Unisys Cromemco Cromemco DOS (CDOS) – a Disk Operating system compatible with CP/M Cromix – a multitasking, multi-user, Unix-like OS for Cromemco microcomputers with Z80A and/or 68000 CPU Data General AOS for 16-bit Data General Eclipse computers and AOS/VS for 32-bit (MV series) Eclipses, MP/AOS for microNOVA-based computers DG/UX RDOS Real-time Disk Operating System, with variants: RTOS and DOS (not related to PC DOS, MS-DOS etc.) Datapoint CTOS Cassette Tape Operating System for the Datapoint 2200 DOS Disk Operating System for the Datapoint 2200, 5500, and 1100 DDC-I, Inc. Deos – Time & Space Partitioned RTOS, Certified to DO-178B, Level A since 1998 HeartOS – POSIX-based Hard Real-Time Operating System Digital Research, Inc. CP/M CP/M CP/M for Intel 8080/8085 and Zilog Z80 Personal CP/M, a refinement of CP/M CP/M Plus with BDOS 3.0 CP/M-68K CP/M for Motorola 68000 CP/M-8000 CP/M for Zilog Z8000 CP/M-86 CP/M for Intel 8088/8086 CP/M-86 Plus Personal CP/M-86 MP/M Multi-user version of CP/M-80 MP/M II MP/M-86 Multi-user version of CP/M-86 MP/M 8-16, a dual-processor variant of MP/M for 8086 and 8080 CPUs. Concurrent CP/M, the successor of CP/M-80 and MP/M-80 Concurrent CP/M-86, the successor of CP/M-86 and MP/M-86 Concurrent CP/M 8-16, a dual-processor variant of Concurrent CP/M for 8086 and 8080 CPUs. Concurrent CP/M-68K, a variant for the 68000 DOS Concurrent DOS, the successor of Concurrent CP/M-86 with PC-MODE Concurrent PC DOS, a Concurrent DOS variant for IBM compatible PCs Concurrent DOS 8-16, a dual-processor variant of Concurrent DOS for 8086 and 8080 CPUs Concurrent DOS 286 Concurrent DOS XM, a real-mode variant of Concurrent DOS with EEMS support Concurrent DOS 386 Concurrent DOS 386/MGE, a Concurrent DOS 386 variant with advanced graphics terminal capabilities Concurrent DOS 68K, a port of Concurrent DOS to Motorola 68000 CPUs with DOS source code portability capabilities FlexOS 1.0 – 2.34, a derivative of Concurrent DOS 286 FlexOS 186, a variant of FlexOS for terminals FlexOS 286, a variant of FlexOS for hosts Siemens S5-DOS/MT, an industrial control system based on FlexOS IBM 4680 OS, a POS operating system based on FlexOS IBM 4690 OS, a POS operating system based on FlexOS Toshiba 4690 OS, a POS operating system based on IBM 4690 OS and FlexOS FlexOS 386, a later variant of FlexOS for hosts IBM 4690 OS, a POS operating system based on FlexOS Toshiba 4690 OS, a POS operating system based on IBM 4690 OS and FlexOS FlexOS 68K, a derivative of Concurrent DOS 68K Multiuser DOS, the successor of Concurrent DOS 386 CCI Multiuser DOS Datapac Multiuser DOS Datapac System Manager, a derivative of Datapac Multiuser DOS IMS Multiuser DOS IMS REAL/32, a derivative of Multiuser DOS IMS REAL/NG, the successor of REAL/32 DOS Plus 1.1 – 2.1, a single-user, multi-tasking system derived from Concurrent DOS 4.1 – 5.0 DR-DOS 3.31 – 6.0, a single-user, single-tasking native DOS derived from Concurrent DOS 6.0 Novell PalmDOS 1.0 Novell "Star Trek" Novell DOS 7, a single-user, multi-tasking system derived from DR DOS Caldera OpenDOS 7.01 Caldera DR-DOS 7.02 and higher Digital Equipment Corporation, Compaq, Hewlett-Packard, Hewlett Packard Enterprise Batch-11/DOS-11 OS/8 RSTS/E – multi-user time-sharing OS for PDP-11s RSX-11 – multiuser, multitasking OS for PDP-11s RT-11 – single user OS for PDP-11 TOPS-10 – for the PDP-10 TENEX – an ancestor of TOPS-20 from BBN, for the PDP-10 TOPS-20 – for the PDP-10 DEC MICA – for the DEC PRISM Digital UNIX – derived from OSF/1, became HP's Tru64 UNIX Ultrix VMS – originally by DEC and HP now by VMS Software Inc.) for the VAX mini-computer range, Alpha and Intel Itanium i2 and i4; later renamed OpenVMS WAITS – for the PDP-6 and PDP-10 ENEA AB OSE – Flexible, small footprint, high-performance RTOS for control processors Fujitsu Towns OS XSP OS/IV MSP MSP-EX General Electric, Honeywell, Bull Real-Time Multiprogramming Operating System GCOS Multics Google Chromium OS is an open source operating system development version of Chrome OS. Both operating systems are based on the Linux kernel. Chrome OS is designed to work exclusively with web applications. Announced on July 7, 2009, Chrome OS is currently publicly available and was released summer 2011. The Chrome OS source code was released on November 19, 2009, under the BSD license as Chromium OS. Container-Optimized OS (COS) is an operating system that is optimized for running Docker containers, based on Chromium OS. Android is an operating system for mobile devices. It consists of Android Runtime (userland) with Linux (kernel), with its Linux kernel modified to add drivers for mobile device hardware and to remove unused Vanilla Linux drivers. gLinux, a Linux distribution that Google uses internally Fuchsia is a capability-based, real-time, operating system (RTOS) scalable to universal devices, in early development, from the tiniest embedded hardware, wristwatches, tablets to the largest personal computers. Unlike Chrome OS and Android, it is not based on the Linux kernel, but instead began on a new microkernel called "Zircon", derived from "Little Kernel". Wear OS a version of Google's Android operating system designed for smartwatches and other wearables. Green Hills Software INTEGRITY – Reliable Operating system INTEGRITY-178B – A DO-178B certified version of INTEGRITY. µ-velOSity – A lightweight microkernel. Harris Corporation Vulcan O/S – Proprietary O/S for Harris' Computer Systems (HCX) Harris UNIX – Proprietary UNIX based OS for Harris' Computers (MCX) Heathkit, Zenith Data Systems HDOS – ran on the H8 and Heath/Zenith Z-89 series HT-11 – a modified version of RT-11 that ran on the Heathkit H11 Hewlett-Packard, Hewlett Packard Enterprise HP Multi-Programming Executive (MPE, MPE/XL, and MPE/iX) – runs on HP 3000 and HP e3000 mini-computers HP-UX – runs on HP9000 and Itanium servers (from small to mainframe-class computers) Honeywell CP-6 Huawei Harmony OS LiteOS Intel Corporation iRMX – real-time operating system originally created to support the Intel 8080 and 8086 processor families in embedded applications. ISIS, ISIS-II – "Intel Systems Implementation Supervisor" was an environment for development of software within the Intel microprocessor family in the early 1980s on their Intellec Microcomputer Development System and clones. ISIS-II worked with 8 inch floppy disks and had an editor, cross-assemblers, a linker, an object locator, debugger, compilers for PL/M, a BASIC interpreter, etc. and allowed file management through a console. IBM On early mainframes: 1410, 7010, 704, 709, 7090, 7094, 7040, 7044, 7030 BESYS – for the IBM 7090 Compatible Time-Sharing System (CTSS) – developed at MIT's Computation Center for use on a modified IBM 7094 FORTRAN Monitor System (FMS) – for the IBM 709 and 7090 GM OS & GM-NAA I/O – for the IBM 704 IBSYS – tape based operating system for IBM 7090 and IBM 7094 7040/7044 Operating System (16/32K) - 7040-PR-150 IJMON – A bootable serial I/O monitor for loading programs for the IBM 1400 series 1410 Processor Operating System (PR-155) for the 1410 and 7010 SHARE Operating System (SOS) – for the IBM 704 and 709 University of Michigan Executive System (UMES) – for the IBM 704, 709, and 7090) On S/360, S/370, and successor mainframes OS/360 and successors on IBM S/360, S/370, and successor mainframes OS/360 (first official OS targeted for the System/360 architecture) PCP (Primary Control Program, a kernel and a ground breaking automatic space allocating file system) MFT (original Multi-programming with a Fixed number of Tasks, replaced by MFT II) MFT II (Multi-Programming with a Fixed number of Tasks, had up to 15 fixed size application partitions, plus partitions for system tasks, initially defined at boot time but redefinable by operator command) MVT (Multi-Programming with a Variable number of Tasks, had up to 15 application regions defined dynamically, plus additional regions for system tasks) M65MP (MVT with support for a multiprocessor 360/65) OS/VS (port of OS/360 targeted for the System/370 virtual memory architecture (OS/370 is not the correct name for OS/VS1 and OS/VS2.) OS/VS has the following variations: OS/VS1 (Operating System/Virtual Storage 1, Virtual-memory version of OS/360 MFT II) OS/VS1 Basic Programming Extensions (BPE) adds device support and VM handshaking OS/VS2 (Operating System/Virtual Storage 2, Virtual-memory version of OS/360 MVT) OS/VS2 R1 (Called Single Virtual Storage (SVS), Virtual-memory version of OS/360 MVT but without multiprocessing support) OS/VS2 R2 through R3.8 (called Multiple Virtual Storage, MVS, eliminated most need for VS1). MVS/SE (MVS System Extensions) MVS/SP (MVS System Product) V1 MVS/370 refers to OS/VS2 MVS, MVS/SE and MVS/SP Version 1 MVS/XA (MVS/SP V2, supports S/370 Extended Architecture, 31-bit addressing) MVS/ESA (MVS supported Enterprise Systems Architecture, horizontal addressing extensions: data only address spaces called Dataspaces) MVS/SP V3 MVS/ESA SP V4 (a Unix environment was available for MVS/ESA SP V4R3) MVS/ESA SP V5 (the UNIX environment was bundled in this and all subsequent versions) OS/390 replacement for MVS/ESA SP V5 with some products bundled z/OS z/Architecture replacement for OS/390 with 64-bit virtual addressing Phoenix/MVS (Developed at Cambridge University) DOS/360 and successors on IBM S/360, S/370, and successor mainframes BOS/360 (early interim version of DOS/360, briefly available at a few Alpha & Beta System/360 sites) TOS/360 (similar to BOS above and more fleeting, able to boot and run from 2x00 series tape drives) DOS/360 (Disk Operating System (DOS), multi-programming system with up to 3 partitions, first commonly available OS for System/360) DOS/360/RJE (DOS/360 with a control program extension that provided for the monitoring of remote job entry hardware (card reader & printer) connected by dedicated phone lines) DOS/VS (First DOS offered on System/370 systems, provided virtual storage) DOS/VSE (also known as VSE, upgrade of DOS/VS, up to 14 fixed size processing partitions ) VSE/Advanced Functions (VSE/AF) - Additional functionality for DOS/VSE VSE/SP (program product including DOS/VSE and VSE/AF) VSE/ESA, replaces VSE/SP, supports ESA/370 and ESA/390 with 31-bit addresses z/VSE (latest version of the four decades old DOS lineage, supports 64-bit addresses, multiprocessing, multiprogramming, SNA, TCP/IP, and some virtual machine features in support of Linux workloads) CP/CMS (Control Program/Cambridge Monitor System) and successors on IBM S/360, S/370, and successor mainframes CP-40/CMS (for System/360 Model 40) CP-67/CMS (for System/360 Model 67) Virtual Machine Facility/370 (VM/370) - the CP virtual machine hypervisor, Conversational Monitor System (CMS) operating system and supporting facilities for System/370 (24-bit addresses) VM/370 Basic System Extensions Program Product (VM/BSE, AKA BSEPP) is an enhancement to VM/370 VM/370 System Extensions Program Product (VM/SE, AKA SEPP) is an enhancement to VM/370 that includes the facilities of VM/BSE Virtual Machine/System Product (VM/SP) replaces VM/370, VM/BSE and VM/SE. Virtual Machine/Extended Architecture (VM/XA) refers to three versions of VM that support System/370 Extended Architecture (S/370-XA) with 31-bit virtual addresses Virtual Machine/Extended architecture Migration Aid (VM/XA MA) - Intended for MVS/370 to MVS/XA migration Virtual Machine/Extended Architecture Systems Facility (VM/XA SF) - new release of VM/XA MA with additional functionality Virtual Machine/Extended Architecture System Product (VM/XA SP) - Replaces VM/SP, VM/SP HPO and VM/XA SF VM/ESA (Virtual Machine/Enterprise Systems Architecture, supports S/370, ESA/370 and ESA/390) z/VM (z/Architecture version of the VM OS with 64-bit addressing) TPF Line (Transaction Processing Facility) on IBM S/360, S/370, and successor mainframes (largely used by airlines) ACP (Airline Control Program) TPF (Transaction Processing Facility) z/TPF (z/Architecture extension) Unix-like on IBM S/360, S/370, and successor mainframes AIX/370 (IBM's Advanced Interactive eXecutive, a System V Unix version) AIX/ESA (IBM's Advanced Interactive eXecutive, a System V Unix version) OpenSolaris for System z UTS (developed by Amdahl) Linux on IBM Z Others on IBM S/360, S/370, and successor mainframes: BOS/360 (Basic Operating System) Distributed Processing Programming Executive/370 (DPPX/370) a port of DDPX from 8100 to S/370. MTS (Michigan Terminal System, developed by a group of universities in the US, Canada, and the UK for the IBM System/360 Model 67, System/370 series, and compatible mainframes) RTOS/360 (IBM's Real Time Operating System, ran on 5 NASA custom System/360-75s) TOS/360 (Tape Operating System) TSS/360 (IBM's Time Sharing System) MUSIC/SP (developed by McGill University for IBM System/370) ORVYL and WYLBUR (developed by Stanford University for IBM System/360) On PC and Intel x86 based architectures PC DOS, IBM DOS PC DOS 1.x, 2.x, 3.x (developed jointly with Microsoft) IBM DOS 4.x, 5.0 (developed jointly with Microsoft) PC DOS 6.1, 6.3, 7, 2000, 7.10 OS/2 OS/2 1.x (developed jointly with Microsoft) OS/2 2.x OS/2 Warp 3 (ported to PPC via Workplace OS) OS/2 Warp 4 eComStation (Warp 4.5/Workspace on Demand, rebundled by Serenity Systems International) ArcaOS (Warp 4.52 based system sold by Arca Noae, LLC) IBM 4680 OS version 1 to 4, a POS operating system based on Digital Research's Concurrent DOS 286 and FlexOS 286 1.xx IBM 4690 OS version 1 to 6.3, a successor to 4680 OS based on Novell's FlexOS 286/FlexOS 386 2.3x Toshiba 4690 OS version 6.4, a successor to 4690 OS 6.3 Unix-like on PS/2 AIX (IBM's Advanced Interactive eXecutive, a System V Unix version) On other hardware platforms IBM Series/1 EDX (Event Driven Executive) RPS (Realtime Programming System) CPS (Control Programming Support, subset of RPS) SerIX (Unix on Series/1) IBM 1130 DMS (Disk Monitor System) IBM 1800 TSX (Time Sharing eXecutive) MPX (Multi Programming eXecutive) IBM 8100 DPCX (Distributed Processing Control eXecutive) DPPX (Distributed Processing Programming Executive) IBM System/3 DMS (Disk Management System) IBM System/34, IBM System/36 SSP (System Support Program) IBM System/38 CPF (Control Program Facility) IBM System/88 Stratus VOS (developed by Stratus, and used for IBM System/88, Original equipment manufacturer from Stratus) IBM AS/400, iSeries, System i, IBM Power Systems IBM i (previously known as OS/400 and i5/OS, descendant of System/38 CPF, includes System/36 SSP and AIX environment) UNIX on IBM RT PC AOS (a BSD Unix version, not related to Data General AOS) AIX (Advanced Interactive eXecutive, a System V Unix version) UNIX on POWER ISA, PowerPC, and Power ISA AIX (Advanced Interactive eXecutive, a System V Unix version) Others Workplace OS (a microkernel based operating system including OS/2, developed and canceled in the 1990s) K42 (open-source research operating system on PowerPC or x86 based cache-coherent multiprocessor systems) Dynix (developed by Sequent, and used for IBM NUMA-Q too) International Computers Limited J and MultiJob – for the System 4 series mainframes GEORGE 2/3/4 GEneral ORGanisational Environment – used by ICL 1900 series mainframes Executive – used on the 1900 and 290x range of minicomputers. A modified version of Executive was also used as part of GEORGE 3 and 4. TME – used on the ME29 minicomputer ICL VME – including early variants VME/B and VME/2900, appearing on the ICL 2900 Series and Series 39 mainframes, implemented in S3 VME/K – on early smaller 2900s Jide Remix OS Jolla Sailfish OS KaiOS KaiOS Lynx Real-time Systems, LynuxWorks, Lynx Software Technologies LynxOS Meizu Flyme OS Micrium Inc. MicroC/OS-II – a small pre-emptive priority based multi-tasking kernel MicroC/OS-III – a small pre-emptive priority based multi-tasking kernel, with unlimited number of tasks and priorities, and round-robin scheduling Microsoft Corporation Xenix (licensed version of Unix; licensed to SCO in 1987) MS-DOS (developed jointly with IBM, versions 1.0–6.22) MSX-DOS (developed by MS Japan for the MSX 8-bit computer) DOS/V OS/2 1.x (developed jointly with IBM until version 1.3) Windows (16-bit and 32-bit preemptive and cooperative multitasking, running atop MS-DOS) Windows 1.0 (Windows 1) Windows 2.0 (Windows 2 – separate version for i386 processor) Windows 3.0 (Windows 3) Windows 3.1x (Windows 3.1) Windows for Workgroups 3.1 (Codename Snowball) Windows 3.2 (Chinese-only release) Windows for Workgroups 3.11 Windows 95 (codename Chicago – Windows 4.0) Windows 98 (codename Memphis – Windows 4.1) Windows Millennium Edition (Windows ME – Windows 4.9) Windows NT (Full 32-bit or 64-bit kernel, not dependent on MS-DOS) Windows NT 3.1 Windows NT 3.5 Windows NT 3.51 Windows NT 4.0 Windows 2000 (Windows NT 5.0) Windows XP (Windows NT 5.1) Windows Server 2003 (Windows NT 5.2) Windows Fundamentals for Legacy PCs (based on Windows XP) Windows Vista (Windows NT 6.0) Windows Azure (Cloud OS Platform) 2009 Windows Home Server (based on Windows Server 2003) Windows Server 2008 (based on Windows Vista) Windows 7 (Windows NT 6.1) Windows Phone 7 Windows Server 2008 R2 (based on Windows 7) Windows Home Server 2011 (based on Windows Server 2008 R2) Windows 8 (Windows NT 6.2) Windows RT Windows Phone 8 Windows Server 2012 (based on Windows 8) Windows 8.1 (Windows NT 6.3) Windows Phone 8.1 Windows Server 2012 R2 (based on Windows 8.1) Windows 10 (Windows NT 10) Windows 10 Mobile Windows Server 2016 Windows Server 2019 Windows 11 Windows CE (OS for handhelds, embedded devices, and real-time applications that is similar to other versions of Windows) Windows CE 3.0 Windows CE 5.0 Windows Embedded CE 6.0 Windows Embedded Compact 7 Windows Embedded Compact 2013 Windows Mobile (based on Windows CE, but for a smaller form factor) Singularity – A research operating system written mostly in managed code (C#) Midori – A managed code operating system Xbox system software Xbox 360 system software Xbox One system software Azure Sphere ThreadX MITS Altair DOS – An early disk operating system for the Altair 8800 machine. MontaVista MontaVista Mobilinux NCR Corporation TMX – Transaction Management eXecutive IMOS – Interactive Multiprogramming Operating System (circa 1978), for the NCR Century 8200 series minicomputers VRX – Virtual Resource eXecutive Nintendo ES is a computer operating system developed originally by Nintendo and since 2008 by Esrille. It is open source and runs natively on x86 platforms. NeXT NeXTSTEP Novell NetWare – network operating system providing high-performance network services. Has been superseded by Open Enterprise Server line, which can be based on NetWare or Linux to provide the same set of services. UnixWare Novell "SuperNOS" – a never released merge of NetWare and UnixWare Novell "Corsair" Novell "Exposé" Open Enterprise Server – the successor to NetWare Open Mobile Platform Aurora OS – the successor to Sailfish OS (not to be confused with a different Aurora OS) Quadros Systems RTXC Quadros RTOS – proprietary C-based RTOS used in embedded systems RCA Time Sharing Operating System (TSOS) – first OS supporting virtual addressing of the main storage and support for both timeshare and batch interface RoweBots DSPnano RTOS – 8/16 Bit Ultra Tiny Embedded Linux Compatible RTOS Samsung Electronics Bada Tizen is an operating system based on the Linux kernel, a project within the Linux Foundation and is governed by a Technical Steering Group (TSG) while controlled by Samsung and backed by Intel. Tizen works on a wide range of Samsung devices including smartphones, tablets, smart TVs, PCs and wearable. Orsay One UI - Android skin Sinclair Research Sinclair BASIC was used in the 8-bit home computers from Sinclair Research and Timex Sinclair. It was included in the ROM, and the computers booted to the Basic interpreter. Various versions exist, with the latter ones supporting disk drive operations. SCO, SCO Group Xenix, Unix System III based distribution for the Intel 8086/8088 architecture Xenix 286, Unix System V Release 2 based distribution for the Intel 80286 architecture Xenix 386, Unix System V Release 2 based distribution for the Intel 80386 architecture SCO Unix, SCO UNIX System V/386 was the first volume commercial product licensed by AT&T to use the UNIX System trademark (1989). Derived from AT&T System V Release 3.2 with an infusion of Xenix device drivers and utilities plus most of the SVR4 features SCO Open Desktop, the first 32-bit graphical user interface for UNIX Systems running on Intel processor-based computers. Based on SCO Unix SCO OpenServer 5, AT&T UNIX System V Release 3 based SCO OpenServer 6, SVR5 (UnixWare 7) based kernel with SCO OpenServer 5 application and binary compatibility, system administration, and user environments UnixWare UnixWare 2.x, based on AT&T System V Release 4.2MP UnixWare 7, UnixWare 2 kernel plus parts of 3.2v5 (UnixWare 2 + OpenServer 5 = UnixWare 7). Referred to by SCO as SVR5 Scientific Data Systems (SDS) Berkeley Timesharing System for the SDS 940 SYSGO PikeOS – a certified real time operating system for safety and security critical embedded systems Tandem Computers, Compaq, Hewlett-Packard, Hewlett Packard Enterprise NonStop OS – runs on HP's NonStop line of Itanium servers Tandy Corporation TRSDOS – A floppy-disk-oriented OS supplied by Tandy/Radio Shack for their TRS-80 Z80-based line of personal computers. Eventually renamed as LS-DOS or LDOS. Color BASIC – A ROM-based OS created by Microsoft for the TRS-80 Color Computer. NewDos/80 – A third-party OS for Tandy's TRS-80 personal computers. DeskMate – Operating system created by Tandy Corporation and introduced with the Tandy 1000 computer. TCSC (later NCSC) Edos – enhanced version of IBM's DOS/360 (and later DOS/VS and DOS/VSE) operating system for System/360 and System/370 IBM mainframes Texas Instruments TI-RTOS Kernel – Real-time operating system for TI's embedded devices. TRON Project TRON – open real-time operating system kernel T-Kernel UNIVAC, Unisys EXEC I EXEC II EXEC 8/OS 1100/OS 2200 VS/9, successor to RCA TSOS Wang Laboratories WPS Wang Word Processing System. Micro-code based system. OIS Wang Office Information System. Successor to the WPS. Combined the WPS and VP/MVP systems. Wind River Systems VxWorks – Small footprint, scalable, high-performance RTOS for embedded microprocessor based systems. Zilog Z80-RIO Other Lisp-based Lisp Machines, Inc. (also known as LMI) used an operating system written in MIT's Lisp Machine Lisp. Symbolics Genera written in a systems dialect of the Lisp programming language called ZetaLisp and Symbolics Common Lisp. Genera was ported to a virtual machine for the DEC Alpha line of computers. Texas Instruments' Explorer Lisp machine workstations also had systems code written in Lisp Machine Lisp. Xerox 1100 series of Lisp machines used an operating system also written in Interlisp, and was also ported to a virtual machine called "Medley." For Elektronika BK ANDOS CSI-DOS MK-DOS Non-standard language-based Pilot operating system – written in the Mesa language and used on Xerox Star workstations. PERQ Operating System (POS) – written in PERQ Pascal. Other proprietary non-Unix-like Эльбрус-1 (Elbrus-1) and Эльбрус-2 – used for application, job control, system programming, implemented in uЭль-76 (AL-76). EOS – developed by ETA Systems for use in their ETA-10 line of supercomputers EMBOS – developed by Elxsi for use on their mini-supercomputers GCOS – a proprietary Operating System originally developed by General Electric MAI Basic Four – An OS implementing Business Basic from MAI Systems. Michigan Terminal System – Developed by a group of universities in the US, Canada, and the UK for use on the IBM System/360 Model 67, the System/370 series, and compatible mainframes MUSIC/SP – an operating system developed for the S/370, running normally under VM OS ES – an operating system for ES EVM PC-MOS/386 – DOS-like, but multiuser/multitasking Prolog-Dispatcher – used to control Soviet Buran space shuttle. SINTRAN III – an operating system used with Norsk Data computers. SkyOS – commercial desktop OS for PCs SODA – used by the Odra 1204 computers. THEOS TSX-32 – a 32-bit operating system for x86 platform. TX990/TXDS, DX10 and DNOS – proprietary operating systems for TI-990 minicomputers Other proprietary Unix-like and POSIX-compliant Aegis (Apollo Computer) Amiga Unix (Amiga ports of Unix System V release 3.2 with Amiga A2500UX and SVR4 with Amiga A3000UX. Started in 1990, last version was in 1992) Coherent (Unix-like OS from Mark Williams Co. for PC class computers) DC/OSx (DataCenter/OSx—an operating system developed by Pyramid Technology for its MIPS-based systems) DG/UX (Data General Corp) DNIX from DIAB DSPnano RTOS (POSIX nanokernel, DSP Optimized, Open Source) HeliOS developed and sold by Perihelion Software mainly for transputer-based systems Interactive Unix (a port of the UNIX System V operating system for Intel x86 by Interactive Systems Corporation) IRIX from SGI MeikOS NeXTSTEP (developed by NeXT; a Unix-based OS based on the Mach microkernel) OS-9 Unix-like RTOS. (OS from Microware for Motorola 6809 based microcomputers) OS9/68K Unix-like RTOS. (OS from Microware for Motorola 680x0 based microcomputers; based on OS-9) OS-9000 Unix-like RTOS. (OS from Microware for Intel x86 based microcomputers; based on OS-9, written in C) OSF/1 (developed into a commercial offering by Digital Equipment Corporation) OPENSTEP QNX (POSIX, microkernel OS; usually a real time embedded OS) Rhapsody (an early form of Mac OS X) RISC iX – derived from BSD 4.3, by Acorn computers, for their ARM family of machines RISC/os (a port by MIPS Technologies of 4.3BSD for its MIPS-based computers) RMX SCO UNIX (from SCO, bought by Caldera who renamed themselves SCO Group) SINIX (a port by SNI of Unix to the MIPS architecture) Solaris (from Sun, bought by Oracle; a System V-based replacement for SunOS) SunOS (BSD-based Unix system used on early Sun hardware) SUPER-UX (a port of System V Release 4.2MP with features adopted from BSD and Linux for NEC SX architecture supercomputers) System V (a release of AT&T Unix, 'SVR4' was the 4th minor release) System V/AT, 386 (The first version of AT&T System V UNIX on the IBM 286 and 386 PCs, ported and sold by Microport) Trusted Solaris (Solaris with kernel and other enhancements to support multilevel security) UniFLEX (Unix-like OS from TSC for DMA-capable, extended addresses, Motorola 6809 based computers; e.g. SWTPC, GIMIX and others) Unicos (the version of Unix designed for Cray Supercomputers, mainly geared to vector calculations) UTX-32 (Developed by Gould CSD (Computer System Division), a Unix-based OS that included both BSD and System V characteristics. It was one of the first Unix based systems to receive NSA's C2 security level certification.) Zenix, Zenith corporations Unix (a popular USA electronics maker at the time) Non-proprietary Unix or Unix-like MINIX (study OS developed by Andrew S. Tanenbaum in the Netherlands) BSD (Berkeley Software Distribution, a variant of Unix for DEC VAX hardware) FreeBSD (one of the outgrowths of UC Regents' abandonment of CSRG's 'BSD Unix') DragonFlyBSD, forked from FreeBSD 4.8 MidnightBSD, forked from FreeBSD 6.1 GhostBSD TrueOS (previously known as PC-BSD) NetBSD (an embedded device BSD variant) OpenBSD forked from NetBSD Bitrig forked from OpenBSD Darwin, created by Apple using code from NeXTSTEP, FreeBSD, and NetBSD GNU (also known as GNU/Hurd) Linux (see also List of Linux distributions) (alleged to be GNU/Linux see GNU/Linux naming controversy) Android Android-x86 Remix OS Redox (written in Rust) OpenSolaris illumos, contains original Unix (SVR4) code derived from the OpenSolaris (discontinued by Oracle in favor of Solaris 11 Express) OpenIndiana, operates under the illumos Foundation. Uses the illumos kernel, which is a derivative of OS/Net, which is basically an OpenSolaris/Solaris kernel with the bulk of the drivers, core libraries, and basic utilities. Nexenta OS, based on the illumos kernel with Ubuntu packages SmartOS, an illumos distribution for cloud computing with Kernel-based Virtual Machine integration. RTEMS (Real-Time Executive for Multiprocessor Systems) Syllable Desktop VSTa Plurix (or Tropix) (by Federal University of Rio de Janeiro – UFRJ) TUNIS (University of Toronto) Xv6 - a simple Unix-like teaching operating system from MIT SerenityOS - aims to be a modern Unix-like operating system, yet with a look and feel that emulates 1990s operating systems such as Microsoft Windows and Mac OS. Non-Unix Cosmos – written in C# FreeDOS – open source DOS variant Genode – operating system framework for microkernels (written in C++) Ghost OS – written in assembly, C/C++ Haiku – open source inspired by BeOS, in development Incompatible Timesharing System (ITS) – written in the MIDAS macro assembler language for the PDP-6 and PDP-10 by MIT students osFree – OS/2 Warp open source clone OSv – written in C++ Phantom OS – persistent object-oriented ReactOS – open source OS designed to be binary compatible with Windows NT and its variants (Windows XP, Windows 2000, etc.); in development SharpOS – written in .NET C# TempleOS – written in HolyC Visopsys – written in C and assembly by Andy McLaughlin Research Unix or Unix-like Plan 9 from Bell Labs – distributed OS developed at Bell Labs, based on original Unix design principles yet functionally different and going much further Inferno – distributed OS derived from Plan 9, originally from Bell Labs Research Unix Non-Unix Amoeba – research OS by Andrew S. Tanenbaum Barrelfish Croquet EROS – microkernel, capability-based CapROS – microkernel EROS successor Harmony – realtime, multitasking, multiprocessing message-passing system developed at the National Research Council of Canada. HelenOS – research and experimental operating system House – Haskell User's Operating System and Environment, research OS written in Haskell and C ILIOS – Research OS designed for routing L4 – second generation microkernel Mach – from OS kernel research at Carnegie Mellon University; see NeXTSTEP Nemesis – Cambridge University research OS – detailed quality of service abilities Singularity – experimental OS from Microsoft Research written in managed code to be highly dependable Spring – research OS from Sun Microsystems THE multiprogramming system – by Dijkstra in 1968, at the Eindhoven University of Technology in the Netherlands, introduced the first form of software-based memory segmentation, freeing programmers from being forced to use actual physical locations Thoth – realtime, multiprocess message-passing system developed at the University of Waterloo. V – from Stanford, early 1980s Verve – OS designed by Microsoft Research to be verified end-to-end for type safety and memory safety Xinu – Study OS developed by Douglas E. Comer in the United States Disk operating systems (DOS) 86-DOS (developed at Seattle Computer Products by Tim Paterson for the new Intel 808x CPUs; licensed to Microsoft, became PC DOS/MS-DOS. Also known by its working title QDOS.) PC DOS (IBM's DOS variant, developed jointly with Microsoft, versions 1.0–7.0, 2000, 7.10) MS-DOS (Microsoft's DOS variant for OEM, developed jointly with IBM, versions 1.x–6.22 Microsoft's now abandoned DOS variant) Concurrent CP/M-86 3.1 (BDOS 3.1) with PC-MODE (Digital Research's successor of CP/M-86 and MP/M-86) Concurrent DOS 3.1-4.1 (BDOS 3.1-4.1) Concurrent PC DOS 3.2 (BDOS 3.2) (Concurrent DOS variant for IBM compatible PCs) DOS Plus 1.1, 1.2 (BDOS 4.1), 2.1 (BDOS 5.0) (single-user, multi-tasking system derived from Concurrent DOS 4.1-5.0) Concurrent DOS 8-16 (dual-processor variant of Concurrent DOS for 8086 and 8080 CPUs) Concurrent DOS 286 1.x FlexOS 1.00-2.34 (derivative of Concurrent DOS 286) FlexOS 186 (variant of FlexOS for terminals) FlexOS 286 (variant of FlexOS for hosts) Siemens S5-DOS/MT (industrial control system based on FlexOS) IBM 4680 OS (POS operating system based on FlexOS) IBM 4690 OS (POS operating system based on FlexOS) Toshiba 4690 OS (POS operating system based on IBM 4690 OS and FlexOS) FlexOS 386 (later variant of FlexOS for hosts) IBM 4690 OS (POS operating system based on FlexOS) Toshiba 4690 OS (POS operating system based on IBM 4690 OS and FlexOS) Concurrent DOS 386 1.0, 1.1, 2.0, 3.0 (BDOS 5.0-6.2) Concurrent DOS 386/MGE (Concurrent DOS 386 variant with advanced graphics terminal capabilities) Multiuser DOS 5.0, 5.01, 5.1 (BDOS 6.3-6.6) (successor of Concurrent DOS 386) CCI Multiuser DOS 5.0-7.22 (up to BDOS 6.6) Datapac Multiuser DOS Datapac System Manager 7 (derivative of Datapac Multiuser DOS) IMS Multiuser DOS 5.1, 7.0, 7.1 (BDOS 6.6-6.7) IMS REAL/32 7.50, 7.51, 7.52, 7.53, 7.54, 7.60, 7.61, 7.62, 7.63, 7.70, 7.71, 7.72, 7.73, 7.74, 7.80, 7.81, 7.82, 7.83, 7.90, 7.91, 7.92, 7.93, 7.94, 7.95 (BDOS 6.8 and higher) (derivative of Multiuser DOS) IMS REAL/NG (successor of REAL/32) Concurrent DOS XM 5.0, 5.2, 6.0, 6.2 (BDOS 5.0-6.2) (real-mode variant of Concurrent DOS with EEMS support) DR DOS 3.31, 3.32, 3.33, 3.34, 3.35, 5.0, 6.0 (BDOS 6.0-7.1) single-user, single-tasking native DOS derived from Concurrent DOS 6.0) Novell PalmDOS 1 (BDOS 7.0) Novell DR DOS "StarTrek" Novell DOS 7 (single-user, multi-tasking system derived from DR DOS, BDOS 7.2) Novell DOS 7 updates 1-10 (BDOS 7.2) Caldera OpenDOS 7.01 (BDOS 7.2) Enhanced DR-DOS 7.01.0x (BDOS 7.2) Dell Real Mode Kernel (DRMK) Novell DOS 7 updates 11-15.2 (BDOS 7.2) Caldera DR-DOS 7.02-7.03 (BDOS 7.3) DR-DOS "WinBolt" OEM DR-DOS 7.04-7.05 (BDOS 7.3) OEM DR-DOS 7.06 (PQDOS) OEM DR-DOS 7.07 (BDOS 7.4/7.7) FreeDOS (open source DOS variant) ProDOS (operating system for the Apple II series computers) PTS-DOS (DOS variant by Russian company Phystechsoft) TurboDOS (Software 2000, Inc.) for Z80 and Intel 8086 processor-based systems Multi-tasking user interfaces and environments for DOS DESQview + QEMM 386 multi-tasking user interface for DOS DESQView/X (X-windowing GUI for DOS) Network operating systems Banyan VINES – by Banyan Systems Cambridge Ring Cisco IOS – by Cisco Systems Cisco NX-OS – previously SAN-OS CTOS – by Convergent Technologies, later acquired by Unisys Data ONTAP – by NetApp ExtremeWare – by Extreme Networks ExtremeXOS – by Extreme Networks Fabric OS – by Brocade JunOS – by Juniper NetWare – networking OS by Novell Network operating system (NOS) – developed by CDC for use in their Cyber line of supercomputers Novell Open Enterprise Server – Open Source networking OS by Novell. Can incorporate either SUSE Linux or Novell NetWare as its kernel Plan 9 – distributed OS developed at Bell Labs, based on Unix design principles but not functionally identical Inferno – distributed OS derived from Plan 9, originally from Bell Labs SONiC TurboDOS – by Software 2000, Inc. Generic, commodity, and other BLIS/COBOL A2 formerly named Active Object System (AOS), and then Bluebottle (a concurrent and active object update to the Oberon operating system) BS1000 by Siemens AG BS2000 by Siemens AG, now BS2000/OSD from Fujitsu-Siemens Computers (formerly Siemens Nixdorf Informationssysteme) BS3000 by Siemens AG (functionally similar to OS-IV and MSP from Fujitsu) Contiki for various, mostly 8-bit systems, including the Apple II series, the Atari 8-bit family, and some Commodore machines. FLEX9 (by Technical Systems Consultants (TSC) for Motorola 6809 based machines; successor to FLEX, which was for Motorola 6800 CPUs) Graphics Environment Manager (GEM) (windowing GUI for CP/M, DOS, and Atari TOS) GEOS (popular windowing GUI for PC, Commodore, Apple computers) JavaOS JNode (Java New Operating System Design Effort), written 99% in Java (native compiled), provides own JVM and JIT compiler. Based on GNU Classpath. JX Java operating system that focuses on a flexible and robust operating system architecture developed as an open source system by the University of Erlangen. KERNAL (default OS on Commodore 64) MERLIN for the Corvus Concept MorphOS (Amiga compatible) MSP by Fujitsu (successor to OS-IV), now MSP/EX, also known as Extended System Architecture (EXA), for 31-bit mode NetWare (networking OS by Novell) Oberon (operating system) (developed at ETH-Zürich by Niklaus Wirth et al.) for the Ceres and Chameleon workstation projects OSD/XC by Fujitsu-Siemens (BS2000 ported to an emulation on a Sun SPARC platform) OS-IV by Fujitsu (based on early versions of IBM's MVS) Pick (often licensed and renamed) PRIMOS by Prime Computer (sometimes spelled PR1MOS and PR1ME) Sinclair QDOS (multitasking for the Sinclair QL computer) SSB-DOS (by Technical Systems Consultants (TSC) for Smoke Signal Broadcasting; a variant of FLEX in most respects) SymbOS (GUI based multitasking operating system for Z80 computers) Symobi (GUI based modern micro-kernel OS for x86, ARM and PowerPC processors, developed by Miray Software; used and developed further at Technical University of Munich) TripOS, 1978 TurboDOS (Software 2000, Inc.) UCSD p-System (portable complete programming environment/operating system/virtual machine developed by a long running student project at UCSD; directed by Prof Kenneth Bowles; written in Pascal) VOS by Stratus Technologies with strong influence from Multics VOS3 by Hitachi for its IBM-compatible mainframes, based on IBM's MVS VM2000 by Siemens AG Visi On (first GUI for early PC machines; not commercially successful) VPS/VM (IBM based, main operating system at Boston University for over 10 years.) Hobby AROS – AROS Research Operating System (formerly known as Amiga Research Operating System) AtheOS – branched to become Syllable Desktop Syllable Desktop – a modern, independently originated OS; see AtheOS BareMetal DSPnano RTOS EmuTOS EROS – Extremely Reliable Operating System HelenOS – based on a preemptible microkernel design LSE/OS MenuetOS – extremely compact OS with GUI, written entirely in FASM assembly language KolibriOS – a fork of MenuetOS SerenityOS ToaruOS PonyOS Embedded Mobile operating systems DIP DOS on Atari Portfolio Embedded Linux (see also Linux for mobile devices) Android Flyme OS Replicant LineageOS See also List of custom Android distributions Firefox OS Ångström distribution Familiar Linux Mæmo based on Debian deployed on Nokia's Nokia 770, N800 and N810 Internet Tablets. OpenZaurus webOS from Palm, Inc., later Hewlett-Packard via acquisition, and most recently at LG Electronics through acquisition from Hewlett-Packard Access Linux Platform bada Openmoko Linux OPhone MeeGo (from merger of Maemo & Moblin) Mobilinux MotoMagx Qt Extended Sailfish OS Tizen (earlier called LiMo Platform) Ubuntu Touch PostmarketOS Inferno (distributed OS originally from Bell Labs) Magic Cap MS-DOS on Poqet PC, HP 95LX, HP 100LX, HP 200LX, HP 1000CX, HP OmniGo 700LX NetBSD Newton OS on Apple MessagePad Palm OS from Palm, Inc; now spun off as PalmSource PEN/GEOS on HP OmniGo 100 and 120 PenPoint OS Plan 9 from Bell Labs PVOS Symbian OS EPOC Windows CE, from Microsoft Pocket PC from Microsoft, a variant of Windows CE Windows Mobile from Microsoft, a variant of Windows CE Windows Phone from Microsoft DSPnano RTOS iOS watchOS tvOS iPod software iPodLinux iriver clix OS RockBox BlackBerry OS PEN/GEOS, GEOS-SC, GEOS-SE Palm OS Symbian platform (successor to Symbian OS) BlackBerry 10 Routers CatOS – by Cisco Systems Cisco IOS – originally Internetwork Operating System by Cisco Systems Inferno – distributed OS originally from Bell Labs IOS-XR – by Cisco Systems JunOS – by Juniper Networks LCOS – by LANCOM Systems Linux OpenWrt DD-WRT LEDE Gargoyle LibreCMC Zeroshell RTOS – by Force10 Networks FreeBSD m0n0wall OPNsense pfsense List of wireless router firmware projects Other embedded Apache Mynewt ChibiOS/RT Contiki ERIKA Enterprise eCos NetBSD Nucleus RTOS NuttX Minix NCOS freeRTOS, openRTOS, safeRTOS OpenEmbedded (or Yocto Project) pSOS (Portable Software On Silicon) QNX – Unix-like real-time operating system, aimed primarily at the embedded systems market. REX OS – microkernel; usually an embedded cell phone OS RIOT ROM-DOS TinyOS ThreadX RT-Thread DSPnano RTOS Windows IoT – formerly Windows Embedded Windows CE Windows IoT Core Windows IoT Enterprise Wind River VxWorks RTOS. Wombat – microkernel; usually real-time embedded Zephyr LEGO Mindstorms brickOS leJOS Capability-based Cambridge CAP computer – operating system demonstrated the use of security capabilities, both in hardware and software, also a useful fileserver, implemented in ALGOL 68C Flex machine – Custom microprogrammable hardware, with an operating system, (modular) compiler, editor, * garbage collector and filing system all written in ALGOL 68. HYDRA – Running on the C.mmp computer at Carnegie Mellon University, implemented in the programming language BLISS KeyKOS nanokernel EROS microkernel CapROS EROS successor V – from Stanford, early 1980s See also Comparison of operating systems Comparison of real-time operating systems Timeline of operating systems Category links Operating systems Embedded operating systems Real-time operating systems References External links "List of Operating Systems". www.operating-system.org. List of operating systems Computing-related lists Operating

Operating System (OS)

OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 relative to Microsoft's new Windows 3.1 operating environment, the two companies severed the relationship in 1992 and OS/2 development fell to IBM exclusively. The name stands for "Operating System/2", because it was introduced as part of the same generation change release as IBM's "Personal System/2 (PS/2)" line of second-generation personal computers. The first version of OS/2 was released in December 1987 and newer versions were released until December 2001. OS/2 was intended as a protected-mode successor of PC DOS. Notably, basic system calls were modeled after MS-DOS calls; their names even started with "Dos" and it was possible to create "Family Mode" applications – text mode applications that could work on both systems. Because of this heritage, OS/2 shares similarities with Unix, Xenix, and Windows NT. IBM discontinued its support for OS/2 on 31 December 2006. Since then, OS/2 has been developed, supported and sold by two different third-party vendors under license from IBM – first by Serenity Systems as eComStation since 2001, and later by Arca Noae LLC as ArcaOS since 2017. Development history 1985–1989: Joint development The development of OS/2 began when IBM and Microsoft signed the "Joint Development Agreement" in August 1985. It was code-named "CP/DOS" and it took two years for the first product to be delivered. OS/2 1.0 was announced in April 1987 and released in December. The original release is textmode-only, and a GUI was introduced with OS/2 1.1 about a year later. OS/2 features an API for controlling the video display (VIO) and handling keyboard and mouse events so that programmers writing for protected-mode need not call the BIOS or access hardware directly. Other development tools included a subset of the video and keyboard APIs as linkable libraries so that family mode programs are able to run under MS-DOS, and, in the OS/2 Extended Edition v1.0, a database engine called Database Manager or DBM (this was related to DB2, and should not be confused with the DBM family of database engines for Unix and Unix-like operating systems). A task-switcher named Program Selector was available through the Ctrl-Esc hotkey combination, allowing the user to select among multitasked text-mode sessions (or screen groups; each can run multiple programs). Communications and database-oriented extensions were delivered in 1988, as part of OS/2 1.0 Extended Edition: SNA, X.25/APPC/LU 6.2, LAN Manager, Query Manager, SQL. The promised user interface, Presentation Manager, was introduced with OS/2 1.1 in October 1988. It had a similar user interface to Windows 2.1, which was released in May of that year. (The interface was replaced in versions 1.2 and 1.3 by a look closer in appearance to Windows 3.0). The Extended Edition of 1.1, sold only through IBM sales channels, introduced distributed database support to IBM database systems and SNA communications support to IBM mainframe networks. In 1989, Version 1.2 introduced Installable Filesystems and, notably, the HPFS filesystem. HPFS provided a number of improvements over the older FAT file system, including long filenames and a form of alternate data streams called Extended Attributes. In addition, extended attributes were also added to the FAT file system. The Extended Edition of 1.2 introduced TCP/IP and Ethernet support. OS/2- and Windows-related books of the late 1980s acknowledged the existence of both systems and promoted OS/2 as the system of the future. 1990: Breakup The collaboration between IBM and Microsoft unravelled in 1990, between the releases of Windows 3.0 and OS/2 1.3. During this time, Windows 3.0 became a tremendous success, selling millions of copies in its first year. Much of its success was because Windows 3.0 (along with MS-DOS) was bundled with most new computers. OS/2, on the other hand, was available only as an additional stand-alone software package. In addition, OS/2 lacked device drivers for many common devices such as printers, particularly non-IBM hardware. Windows, on the other hand, supported a much larger variety of hardware. The increasing popularity of Windows prompted Microsoft to shift its development focus from cooperating on OS/2 with IBM to building its own business based on Windows. Several technical and practical reasons contributed to this breakup. The two companies had significant differences in culture and vision. Microsoft favored the open hardware system approach that contributed to its success on the PC. IBM sought to use OS/2 to drive sales of its own hardware, and urged Microsoft to drop features, such as fonts, that IBM's hardware did not support. Microsoft programmers also became frustrated with IBM's bureaucracy and its use of lines of code to measure programmer productivity. IBM developers complained about the terseness and lack of comments in Microsoft's code, while Microsoft developers complained that IBM's code was bloated. The two products have significant differences in API. OS/2 was announced when Windows 2.0 was near completion, and the Windows API already defined. However, IBM requested that this API be significantly changed for OS/2. Therefore, issues surrounding application compatibility appeared immediately. OS/2 designers hoped for source code conversion tools, allowing complete migration of Windows application source code to OS/2 at some point. However, OS/2 1.x did not gain enough momentum to allow vendors to avoid developing for both OS/2 and Windows in parallel. OS/2 1.x targets the Intel 80286 processor and DOS fundamentally doesn't. IBM insisted on supporting the 80286 processor, with its 16-bit segmented memory mode, because of commitments made to customers who had purchased many 80286-based PS/2s as a result of IBM's promises surrounding OS/2. Until release 2.0 in April 1992, OS/2 ran in 16-bit protected mode and therefore could not benefit from the Intel 80386's much simpler 32-bit flat memory model and virtual 8086 mode features. This was especially painful in providing support for DOS applications. While, in 1988, Windows/386 2.1 could run several cooperatively multitasked DOS applications, including expanded memory (EMS) emulation, OS/2 1.3, released in 1991, was still limited to one "DOS box". Given these issues, Microsoft started to work in parallel on a version of Windows which was more future-oriented and more portable. The hiring of Dave Cutler, former VAX/VMS architect, in 1988 created an immediate competition with the OS/2 team, as Cutler did not think much of the OS/2 technology and wanted to build on his work on the MICA project at Digital rather than creating a "DOS plus". His NT OS/2 was a completely new architecture. IBM grew concerned about the delays in development of OS/2 2.0. Initially, the companies agreed that IBM would take over maintenance of OS/2 1.0 and development of OS/2 2.0, while Microsoft would continue development of OS/2 3.0. In the end, Microsoft decided to recast NT OS/2 3.0 as Windows NT, leaving all future OS/2 development to IBM. From a business perspective, it was logical to concentrate on a consumer line of operating systems based on DOS and Windows, and to prepare a new high-end system in such a way as to keep good compatibility with existing Windows applications. While it waited for this new high-end system to develop, Microsoft would still receive licensing money from Xenix and OS/2 sales. Windows NT's OS/2 heritage can be seen in its initial support for the HPFS filesystem, text mode OS/2 1.x applications, and OS/2 LAN Manager network support. Some early NT materials even included OS/2 copyright notices embedded in the software. One example of NT OS/2 1.x support is in the WIN2K resource kit. Windows NT could also support OS/2 1.x Presentation Manager and AVIO applications with the addition of the Windows NT Add-On Subsystem for Presentation Manager. 1992: 32-bit era OS/2 2.0 was released in April 1992. At the time, the suggested retail price was U.S. $195, while Windows retailed for $150. OS/2 2.0 provided a 32-bit API for native programs, though the OS itself still contained some 16-bit code and drivers. It also included a new OOUI (object-oriented user interface) called the Workplace Shell. This was a fully object-oriented interface that was a significant departure from the previous GUI. Rather than merely providing an environment for program windows (such as the Program Manager), the Workplace Shell provided an environment in which the user could manage programs, files and devices by manipulating objects on the screen. With the Workplace Shell, everything in the system is an "object" to be manipulated. DOS compatibility OS/2 2.0 was touted by IBM as "a better DOS than DOS and a better Windows than Windows". It managed this by including the fully-licensed MS-DOS 5.0, which had been patched and improved upon. For the first time, OS/2 was able to run more than one DOS application at a time. This was so effective, that it allowed OS/2 to run a modified copy of Windows 3.0, itself a DOS extender, including Windows 3.0 applications. Because of the limitations of the Intel 80286 processor, OS/2 1.x could run only one DOS program at a time, and did this in a way that allowed the DOS program to have total control over the computer. A problem in DOS mode could crash the entire computer. In contrast, OS/2 2.0 could leverage the virtual 8086 mode of the Intel 80386 processor to create a much safer virtual machine in which to run DOS programs. This included an extensive set of configuration options to optimize the performance and capabilities given to each DOS program. Any real-mode operating system (such as 8086 Xenix) could also be made to run using OS/2's virtual machine capabilities, subject to certain direct hardware access limitations. Like most 32-bit environments, OS/2 could not run protected-mode DOS programs using the older VCPI interface, unlike the Standard mode of Windows 3.1; it only supported programs written according to DPMI. (Microsoft discouraged the use of VCPI under Windows 3.1, however, due to performance degradation.) Unlike Windows NT, OS/2 always allowed DOS programs the possibility of masking real hardware interrupts, so any DOS program could deadlock the machine in this way. OS/2 could, however, use a hardware watchdog on selected machines (notably IBM machines) to break out of such a deadlock. Later, release 3.0 leveraged the enhancements of newer Intel 80486 and Intel Pentium processors—the Virtual Interrupt Flag (VIF), which was part of the Virtual Mode Extensions (VME)—to solve this problem. Windows 3.x compatibility Compatibility with Windows 3.0 (and later Windows 3.1) was achieved by adapting Windows user-mode code components to run inside a virtual DOS machine (VDM). Originally, a nearly complete version of Windows code was included with OS/2 itself: Windows 3.0 in OS/2 2.0, and Windows 3.1 in OS/2 2.1. Later, IBM developed versions of OS/2 that would use whatever Windows version the user had installed previously, patching it on the fly, and sparing the cost of an additional Windows license. It could either run full-screen, using its own set of video drivers, or "seamlessly," where Windows programs would appear directly on the OS/2 desktop. The process containing Windows was given fairly extensive access to hardware, especially video, and the result was that switching between a full-screen WinOS/2 session and the Workplace Shell could occasionally cause issues. Because OS/2 only runs the user-mode system components of Windows, it is incompatible with Windows device drivers (VxDs) and applications that require them. Multiple Windows applications run by default in a single Windows session – multitasking cooperatively and without memory protection – just as they would under native Windows 3.x. However, to achieve true isolation between Windows 3.x programs, OS/2 can also run multiple copies of Windows in parallel, with each copy residing in a separate VDM. The user can then optionally place each program either in its own Windows session – with preemptive multitasking and full memory protection between sessions, though not within them – or allow some applications to run together cooperatively in a shared Windows session while isolating other applications in one or more separate Windows sessions. At the cost of additional hardware resources, this approach can protect each program in any given Windows session (and each instance of Windows itself) from every other program running in any separate Windows session (though not from other programs running in the same Windows session). Whether Windows applications are running in full-screen or windowed mode, and in one Windows session or several, it is possible to use DDE between OS/2 and Windows applications, and OLE between Windows applications only. 1994: OS/2 Warp Released in 1994, OS/2 version 3.0 was labelled as OS/2 Warp to highlight the new performance benefits, and generally to freshen the product image. "Warp" had originally been the internal IBM name for the release: IBM claimed that it had used Star Trek terms as internal names for prior OS/2 releases, and that this one seemed appropriate for external use as well. At the launch of OS/2 Warp in 1994, Patrick Stewart was to be the Master of Ceremonies; however Kate Mulgrew of the then-upcoming series Star Trek: Voyager substituted him at the last minute. OS/2 Warp offers a host of benefits over OS/2 2.1, notably broader hardware support, greater multimedia capabilities, Internet-compatible networking, and it includes a basic office application suite known as IBM Works. It was released in two versions: the less expensive "Red Spine" and the more expensive "Blue Spine" (named for the color of their boxes). "Red Spine" was designed to support Microsoft Windows applications by utilizing any existing installation of Windows on the computer's hard drive. "Blue Spine" includes Windows support in its own installation, and so can support Windows applications without a Windows installation. As most computers were sold with Microsoft Windows pre-installed and the price was less, "Red Spine" was the more popular product. OS/2 Warp Connect—which has full LAN client support built-in—followed in mid-1995. Warp Connect was nicknamed "Grape". In OS/2 2.0, most performance-sensitive subsystems, including the graphics (Gre) and multimedia (MMPM/2) systems, were updated to 32-bit code in a fixpack, and included as part of OS/2 2.1. Warp 3 brought about a fully 32-bit windowing system, while Warp 4 introduced the object-oriented 32-bit GRADD display driver model. 1996: Warp 4 In 1996, Warp 4 added Java and speech recognition software. IBM also released server editions of Warp 3 and Warp 4 which bundled IBM's LAN Server product directly into the operating system installation. A personal version of Lotus Notes was also included, with a number of template databases for contact management, brainstorming, and so forth. The UK-distributed free demo CD-ROM of OS/2 Warp essentially contained the entire OS and was easily, even accidentally, cracked, meaning that even people who liked it did not have to buy it. This was seen as a backdoor tactic to increase the number of OS/2 users, in the belief that this would increase sales and demand for third-party applications, and thus strengthen OS/2's desktop numbers. This suggestion was bolstered by the fact that this demo version had replaced another which was not so easily cracked, but which had been released with trial versions of various applications. In 2000, the July edition of Australian Personal Computer magazine bundled software CD-ROMs, included a full version of Warp 4 that required no activation and was essentially a free release. Special versions of OS/2 2.11 and Warp 4 also included symmetric multiprocessing (SMP) support. OS/2 sales were largely concentrated in networked computing used by corporate professionals; however, by the early 1990s, it was overtaken by Microsoft Windows NT. While OS/2 was arguably technically superior to Microsoft Windows 95, OS/2 failed to develop much penetration in the consumer and stand-alone desktop PC segments; there were reports that it could not be installed properly on IBM's own Aptiva series of home PCs. Microsoft made an offer in 1994 where IBM would receive the same terms as Compaq (the largest PC manufacturer at the time) for a license of Windows 95, if IBM ended development of OS/2 completely. IBM refused and instead went with an "IBM First" strategy of promoting OS/2 Warp and disparaging Windows, as IBM aimed to drive sales of its own software as well as hardware. By 1995, Windows 95 negotiations between IBM and Microsoft, which were already difficult, stalled when IBM purchased Lotus SmartSuite, which would have directly competed with Microsoft Office. As a result of the dispute, IBM signed the license agreement 15 minutes before Microsoft's Windows 95 launch event, which was later than their competitors and this badly hurt sales of IBM PCs. IBM officials later conceded that OS/2 would not have been a viable operating system to keep them in the PC business. Workplace OS In 1991, IBM started development on an intended replacement for OS/2 called Workplace OS. This was an entirely new product, brand new code, that borrowed only a few sections of code from both the existing OS/2 and AIX products. It used an entirely new microkernel code base, intended (eventually) to host several of IBM's operating systems (including OS/2) as microkernel "personalities". It also included major new architectural features including a system registry, JFS, support for UNIX graphics libraries, and a new driver model. Workplace OS was developed solely for POWER platforms, and IBM intended to market a full line of PowerPCs in an effort to take over the market from Intel. A mission was formed to create prototypes of these machines and they were disclosed to several corporate customers, all of whom raised issues with the idea of dropping Intel. Advanced plans for the new code base would eventually include replacement of the OS/400 operating system by Workplace OS, as well as a microkernel product that would have been used in industries such as telecommunications and set-top television receivers. A partially functional pre-alpha version of Workplace OS was demonstrated at Comdex, where a bemused Bill Gates stopped by the booth. The second and last time it would be shown in public was at an OS/2 user group in Phoenix, Arizona; the pre-alpha code refused to boot. It was released in 1995. But with $990 million being spent per year on development of this as well as Workplace OS, and no possible profit or widespread adoption, the end of the entire Workplace OS and OS/2 product line was near. Downsizing A project was launched internally by IBM to evaluate the looming competitive situation with Microsoft Windows 95. Primary concerns included the major code quality issues in the existing OS/2 product (resulting in over 20 service packs, each requiring more diskettes than the original installation), and the ineffective and heavily matrixed development organization in Boca Raton (where the consultants reported that "basically, everybody reports to everybody") and Austin. That study, tightly classified as "Registered Confidential" and printed only in numbered copies, identified untenable weaknesses and failures across the board in the Personal Systems Division as well as across IBM as a whole. This resulted in a decision being made at a level above the Division to cut over 95% of the overall budget for the entire product line, end all new development (including Workplace OS), eliminate the Boca Raton development lab, end all sales and marketing efforts of the product, and lay off over 1,300 development individuals (as well as sales and support personnel). $990 million had been spent in the last full year. Warp 4 became the last distributed version of OS/2. 2001: Fading out A small and dedicated community remained faithful to OS/2 for many years after its final mainstream release, but overall, OS/2 failed to catch on in the mass market and is little used outside certain niches where IBM traditionally had a stronghold. For example, many bank installations, especially automated teller machines, run OS/2 with a customized user interface; French SNCF national railways used OS/2 1.x in thousands of ticket selling machines. Telecom companies such as Nortel used OS/2 in some voicemail systems. Also, OS/2 was used for the host PC used to control the Satellite Operations Support System equipment installed at NPR member stations from 1994 to 2007, and used to receive the network's programming via satellite. Although IBM began indicating shortly after the release of Warp 4 that OS/2 would eventually be withdrawn, the company did not end support until December 31, 2006. Sales of OS/2 stopped on December 23, 2005. The latest IBM OS/2 Warp version is 4.52, which was released for both desktop and server systems in December 2001. IBM is still delivering defect support for a fee. IBM urges customers to migrate their often highly complex applications to e-business technologies such as Java in a platform-neutral manner. Once application migration is completed, IBM recommends migration to a different operating system, suggesting Linux as an alternative. Third-party development After IBM discontinued development of OS/2, various third parties approached IBM to take over future development of the operating system. The OS/2 software vendor Stardock made such a proposal to IBM in 1999, but it was not followed through by the company. Serenity Systems succeeded in negotiating an agreement with IBM, and began reselling OS/2 as eComStation in 2001. eComStation is now sold by XEU.com, the most recent version (2.1) was released in 2011. In 2015, Arca Noae, LLC announced that they had secured an agreement with IBM to resell OS/2. They released the first version of their OS/2-based operating system in 2017 as ArcaOS. As of 2021, there have been multiple releases of ArcaOS, and it remains under active development. Petitions for open source Many people hoped that IBM would release OS/2 or a significant part of it as open source. Petitions were held in 2005 and 2007, but IBM refused them, citing legal and technical reasons. It is unlikely that the entire OS will be open at any point in the future because it contains third-party code to which IBM does not have copyright, and much of this code is from Microsoft. IBM also once engaged in a technology transfer with Commodore, licensing Amiga technology for OS/2 2.0 and above, in exchange for the REXX scripting language. This means that OS/2 may have some code that was not written by IBM, which can therefore prevent the OS from being re-announced as open-sourced in the future. On the other hand, IBM donated Object REXX for Windows and OS/2 to the Open Object REXX project maintained by the REXX Language Association on SourceForge. There was a petition, arranged by OS2World, to open parts of the OS. Open source operating systems such as Linux have already profited from OS/2 indirectly through IBM's release of the improved JFS file system, which was ported from the OS/2 code base. As IBM didn't release the source of the OS/2 JFS driver, developers ported the Linux driver back to eComStation and added the functionality to boot from a JFS partition. This new JFS driver has been integrated into eComStation v2.0, and later into ArcaOS 5.0. Summary of releases Release dates refer to the US English editions unless otherwise noted. Features and technology User interface The graphic system has a layer named Presentation Manager that manages windows, fonts, and icons. This is similar in functionality to a non-networked version of X11 or the Windows GDI. On top of this lies the Workplace Shell (WPS) introduced in OS/2 2.0. WPS is an object-oriented shell allowing the user to perform traditional computing tasks such as accessing files, printers, launching legacy programs, and advanced object oriented tasks using built-in and third-party application objects that extended the shell in an integrated fashion not available on any other mainstream operating system. WPS follows IBM's Common User Access user interface standards. WPS represents objects such as disks, folders, files, program objects, and printers using the System Object Model (SOM), which allows code to be shared among applications, possibly written in different programming languages. A distributed version called DSOM allowed objects on different computers to communicate. DSOM is based on CORBA. The object oriented aspect of SOM is similar to, and a direct competitor to, Microsoft's Component Object Model, though it is implemented in a radically different manner; for instance, one of the most notable differences between SOM and COM is SOM's support for inheritance (one of the most fundamental concepts of OO programming)—COM does not have such support. SOM and DSOM are no longer being developed. The multimedia capabilities of OS/2 are accessible through Media Control Interface commands. The last update (bundled with the IBM version of Netscape Navigator plugins) added support for MPEG files. Support for newer formats such as PNG, progressive JPEG, DivX, Ogg, and MP3 comes from third parties. Sometimes it is integrated with the multimedia system, but in other offers it comes as standalone applications. Commands The following list of commands is supported by cmd.exe on OS/2. ansi append assign attrib backup boot break cache call cd chcp chdir chkdsk cls cmd codepage command comp copy createdd date ddinstal debug del detach dir diskcomp diskcopy doskey dpath eautil echo endlocal erase exit extproc fdisk fdiskpm find for format fsaccess goto graftabl help if join keyb keys label makeini md mem mkdir mode more move patch path pause picview pmrexx print prompt pstat rd recover rem ren rename replace restore rmdir set setboot setcom40 setlocal share shift sort spool start subst syslevel syslog time trace tracebuf tracefmt tree type undelete unpack ver verify view vmdisk vol xcopy Networking The TCP/IP stack is based on the open source BSD stack as visible with SCCS what compatible tools. IBM included tools such as ftp and telnet and even servers for both commands. IBM sold several networking extensions including NFS support and an X11 server. Drivers Hardware vendors were reluctant to support device drivers for alternative operating systems including OS/2, leaving users with few choices from a select few vendors. To relieve this issue for video cards, IBM licensed a reduced version of the Scitech display drivers, allowing users to choose from a wide selection of cards supported through Scitech's modular driver design. Virtualization OS/2 has historically been more difficult to run in a virtual machine than most other legacy x86 operating systems because of its extensive reliance on the full set of features of the x86 CPU; in particular, OS/2's use of ring 2 prevented it from running in early versions of VMware. Newer versions of VMware provide official support for OS/2, specifically for eComStation. VirtualPC from Microsoft (originally Connectix) has been able to run OS/2 without hardware virtualization support for many years. It also provided "additions" code which greatly improves host–guest OS interactions in OS/2. The additions are not provided with the current version of VirtualPC, but the version last included with a release may still be used with current releases. At one point, OS/2 was a supported host for VirtualPC in addition to a guest. Note that OS/2 runs only as a guest on those versions of VirtualPC that use virtualization (x86 based hosts) and not those doing full emulation (VirtualPC for Mac). VirtualBox from Oracle Corporation (originally InnoTek, later Sun) supports OS/2 1.x, Warp 3 through 4.5, and eComStation as well as "Other OS/2" as guests. However, attempting to run OS/2 and eComStation can still be difficult, if not impossible, because of the strict requirements of VT-x/AMD-V hardware-enabled virtualization and only ACP2/MCP2 is reported to work in a reliable manner. ArcaOS supports being run as a virtual machine guest inside VirtualBox, VMware ESXi and VMWare Workstation. It ships with VirtualBox Guest Additions, and driver improvements to improve performance as a guest operating system. The difficulties in efficiently running OS/2 have, at least once, created an opportunity for a new virtualization company. A large bank in Moscow needed a way to use OS/2 on newer hardware that OS/2 did not support. As virtualization software is an easy way around this, the company desired to run OS/2 under a hypervisor. Once it was determined that VMware was not a possibility, it hired a group of Russian software developers to write a host-based hypervisor that would officially support OS/2. Thus, the Parallels, Inc. company and their Parallels Workstation product was born. Security niche OS/2 has few native computer viruses; while it is not invulnerable by design, its reduced market share appears to have discouraged virus writers. There are, however, OS/2-based antivirus programs, dealing with DOS viruses and Windows viruses that could pass through an OS/2 server. Problems Some problems were classic subjects of comparison with other operating systems: Synchronous input queue (SIQ): if a GUI application was not servicing its window messages, the entire GUI system could get stuck and a reboot was required. This problem was considerably reduced with later Warp 3 fixpacks and refined by Warp 4, by taking control over the application after it had not responded for several seconds. No unified object handles (OS/2 v2.11 and earlier): The availability of threads probably led system designers to overlook mechanisms which allow a single thread to wait for different types of asynchronous events at the same time, for example the keyboard and the mouse in a "console" program. Even though select was added later, it only worked on network sockets. In case of a console program, dedicating a separate thread for waiting on each source of events made it difficult to properly release all the input devices before starting other programs in the same "session". As a result, console programs usually polled the keyboard and the mouse alternately, which resulted in wasted CPU and a characteristic "jerky" reactivity to user input. In OS/2 3.0 IBM introduced a new call for this specific problem. Historical uses OS/2 has been widely used in Iran Export Bank (Bank Saderat Iran) in their teller machines, ATMs and local servers (over 30,000 working stations). As of 2011, the bank moved to virtualize and renew their infrastructure by moving OS/2 to Virtual Machines running over Windows. OS/2 was widely used in Brazilian banks. Banco do Brasil had a peak 10,000 machines running OS/2 Warp in the 1990s. OS/2 was used in automated teller machines until 2006. The workstations and automated teller machines and attendant computers have been migrated to Linux. OS/2 has been used in the banking industry. Suncorp bank in Australia still ran its ATM network on OS/2 as late as 2002. ATMs at Perisher Blue used OS/2 as late as 2009, and even the turn of the decade. OS/2 was widely adopted by accounting professionals and auditing companies. In mid-1990s native 32-bit accounting software were well developed and serving corporate markets. OS/2 ran the faulty baggage handling system at Denver International Airport. The OS was eventually scrapped, but the software written for the system led to massive delays in the opening of the new airport. The OS itself was not at fault, but the software written to run on the OS was. The baggage handling system was eventually removed. OS/2 was used by radio personality Howard Stern. He once had a 10-minute on-air rant about OS/2 versus Windows 95 and recommended OS/2. He also used OS/2 on his IBM 760CD laptop. OS/2 was used as part of the Satellite Operations Support System (SOSS) for NPR's Public Radio Satellite System. SOSS was a computer-controlled system using OS/2 that NPR member stations used to receive programming feeds via satellite. SOSS was introduced in 1994 using OS/2 3.0, and was retired in 2007, when NPR switched over to its successor, the ContentDepot. OS/2 was used to control the SkyTrain automated light rail system in Vancouver, Canada until the late 2000s when it was replaced by Windows XP. OS/2 was used in the London Underground Jubilee Line Extension Signals Control System (JLESCS) in London, England. This control system delivered by Alcatel was in use from 1999 to 2011 i.e. between abandonment before opening of the line's unimplemented original automatic train control system and the present SelTrac system. JLESCS did not provide automatic train operation only manual train supervision. Six OS/2 local site computers were distributed along the railway between Stratford and Westminster, the shunting tower at Stratford Market Depot, and several formed the central equipment located at Neasden Depot. It was once intended to cover the rest of the line between Green Park and Stanmore but this was never introduced. OS/2 has been used by The Co-operative Bank in the UK for its domestic call centre staff, using a bespoke program created to access customer accounts which cannot easily be migrated to Windows. OS/2 has been used by the Stop & Shop supermarket chain (and has been installed in new stores as recently as March 2010). OS/2 has been used on ticket machines for Tramlink in outer-London. OS/2 has been used in New York City's subway system for MetroCards. Rather than interfacing with the user, it connects simple computers and the mainframes. When NYC MTA finishes its transition to contactless payment, OS/2 will be removed. OS/2 was used in checkout systems at Safeway supermarkets. OS/2 was used by Trenitalia, both for the desktops at Ticket Counters and for the Automatic Ticket Counters up to 2011. Incidentally, the Automatic Ticket Counters with OS/2 were more reliable than the current ones running a flavor of Windows. OS/2 was used as the main operating system for Abbey National General Insurance motor and home direct call centre products using the PMSC Series III insurance platform on DB2.2 from 1996-2001. Awards BYTE in 1989 listed OS/2 as among the "Excellence" winners of the BYTE Awards, stating that it "is today where the Macintosh was in 1984: It's a development platform in search of developers". The magazine predicted that "When it's complete and bug-free, when it can really use the 80386, and when more desktops sport OS/2-capable PCs, OS/2 will—deservedly—supersede DOS. But even as it stands, OS/2 is a milestone product". In March 1995 OS/2 won seven awards InfoWorld Product of the Year. Five Awards at CeBIT. PC Professional Magazine - Innovation of the Year award. CHIP Magazine named OS/2 Warp the Operating System of the Year. DOS International named OS/2 Warp the Operating System of the Year. 1+1 Magazine awarded it with the Software Marketing Quality award. Industrie Forum awarded it with its Design Excellence. SPA Best Business Software Award. IBM products utilizing OS/2 IBM has used OS/2 in a wide variety of hardware products, effectively as a form of embedded operating system. See also History of the graphical user interface Multiple Virtual DOS Machine (MVDM) - OS/2 virtual DOS machine and seamless Windows integration Team OS/2 Windows Libraries for OS/2 LAN Manager References Further reading —Necasek discusses an aborted port to PowerPC machines. External links os2world.com – Community of OS/2 users ecomstation.ru – Community of eComStation and OS/2 users netlabs.org – OpenSource Software for OS/2 and eCS OS/2 FAQ hobbes.nmsu.edu – The OS/2 software repository EDM/2 – The source for OS/2 developers eCSoft/2 – The OS/2 and eComstation software guide osFree an open source project to build an OS/2 clone operating system Voyager Project, a defunct project to reimplement OS/2 on modern technology OS/2 to Linux API porting project Open Source OS/2 API implementation for Windows Microsoft documentation of OS/2 API compatibility with Windows NT The History of OS/2 Technical details of OS/2 OS/2 Warp 4 Installation and Update Manual; with boot disks and many links 1987 software Discontinued operating systems IBM operating systems Legacy systems Star Trek fandom X86 operating systems

Operating System (OS)

S-OS S-OS is a simple operating system mainly for Z80 based computers. The operating system was first presented in 1986 in the Japanese magazine Oh!X in an article called "The Sentinel". Commands The command and command set is very simplified. Directory #D [<device name>:] Change default device (S=startup, A=tape..) #DV <device name>: Jump to address (and run program) #J <address> Load the program #L <filename>[:<address>] Enter the machine specific monitor #M Delete the file #K <file name> Save a memory block to file #S <filename>: <start address>: <end address>[: <execution address>] Exit from S-OS and reboot #! Supported systems Sharp MZ-80K/C/1200 Sharp MZ-700 / 1500 Sharp MZ-80B / 2000 / 2200 Sharp MZ-2500/2861(MZ-2500 mode) Sharp X1/C/D/Cs/Ck/F/G/Twin (two different implementations) Sharp X1turbo/II/III/Z/ZII/ZIII NEC PC-8001/8801 NEC PC-6001mkII/6601/SR Sony SMC-777C Toshiba PASOPIA Fujitsu FM-7 / 77 (Z80 extension card) Sharp X68000 (emulated Z80) PC-286/NEC PC-9801 (emulated Z80) MSX 2 / 2+ / turboR Casio FP-1000 / 1100 Windows 32 bit (emulated Z80) Sharp calculators PC-G850/S/V/VS References External links http://www.retropc.net/ohishi/s-os/ http://homepage2.nifty.com/akikawa/sword/index.html http://www16.ocn.ne.jp/~ver0/g800/#sos Microcomputer software ja:Oh!X#THE_SENTINEL

Operating System (OS)

Microsoft Windows Microsoft Windows, commonly referred to as Windows, is a group of several proprietary graphical operating system families, all of which are developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. Active Microsoft Windows families include Windows NT and Windows IoT; these may encompass subfamilies, (e.g. Windows Server or Windows Embedded Compact) (Windows CE). Defunct Microsoft Windows families include Windows 9x, Windows Mobile and Windows Phone. Microsoft introduced an operating environment named Windows on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Microsoft Windows came to dominate the world's personal computer (PC) market with over 90% market share, overtaking Mac OS, which had been introduced in 1984. Apple came to see Windows as an unfair encroachment on their innovation in GUI development as implemented on products such as the Lisa and Macintosh (eventually settled in court in Microsoft's favor in 1993). On PCs, Windows is still the most popular operating system in all countries. However, in 2014, Microsoft admitted losing the majority of the overall operating system market to Android, because of the massive growth in sales of Android smartphones. In 2014, the number of Windows devices sold was less than 25% that of Android devices sold. This comparison, however, may not be fully relevant, as the two operating systems traditionally target different platforms. Still, numbers for server use of Windows (that are comparable to competitors) show one third market share, similar to that for end user use. , the most recent version of Windows for PCs and tablets is Windows 11, version 21H2. The most recent version for embedded devices is Windows 10, version 21H1. The most recent version for server computers is Windows Server 2022, version 21H2. A specialized version of Windows also runs on the Xbox One and Xbox Series X/S video game consoles. Genealogy By marketing role Microsoft, the developer of Windows, has registered several trademarks, each of which denotes a family of Windows operating systems that target a specific sector of the computing industry. As of 2014, the following Windows families were being actively developed: Windows NT: Started as a family of operating systems with Windows NT 3.1, an operating system for server computers and workstations. It now consists of three operating system subfamilies that are released almost at the same time and share the same kernel: Windows: The operating system for mainstream personal computers and tablets. The latest version is Windows 11. The main competitor of this family is macOS by Apple for personal computers and iPadOS and Android for tablets (c.f. ). Windows Server: The operating system for server computers. The latest version is Windows Server 2022. Unlike its client sibling, it has adopted a strong naming scheme. The main competitor of this family is Linux. (c.f. ) Windows PE: A lightweight version of its Windows sibling, meant to operate as a live operating system, used for installing Windows on bare-metal computers (especially on many computers at once), recovery or troubleshooting purposes. The latest version is Windows PE 10. Windows IoT (previously Windows Embedded): Initially, Microsoft developed Windows CE as a general-purpose operating system for every device that was too resource-limited to be called a full-fledged computer. Eventually, however, Windows CE was renamed Windows Embedded Compact and was folded under Windows Compact trademark which also consists of Windows Embedded Industry, Windows Embedded Professional, Windows Embedded Standard, Windows Embedded Handheld and Windows Embedded Automotive. The following Windows families are no longer being developed: Windows 9x: An operating system that targeted the consumer market. Discontinued because of suboptimal performance. (PC World called its last version, Windows Me, one of the worst products of all time.) Microsoft now caters to the consumer market with Windows NT. Windows Mobile: The predecessor to Windows Phone, it was a mobile phone operating system. The first version was called Pocket PC 2000; the third version, Windows Mobile 2003 is the first version to adopt the Windows Mobile trademark. The last version is Windows Mobile 6.5. Windows Phone: An operating system sold only to manufacturers of smartphones. The first version was Windows Phone 7, followed by Windows Phone 8, and Windows Phone 8.1. It was succeeded by Windows 10 Mobile, that is now also discontinued. Version history The term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are generally categorized as follows: Early versions The history of Windows dates back to 1981 when Microsoft started work on a program called "Interface Manager". It was announced in November 1983 (after the Apple Lisa, but before the Macintosh) under the name "Windows", but Windows 1.0 was not released until November 1985. Windows 1.0 was to compete with Apple's operating system, but achieved little popularity. Windows 1.0 is not a complete operating system; rather, it extends MS-DOS. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Components included Calculator, Calendar, Cardfile, Clipboard Viewer, Clock, Control Panel, Notepad, Paint, Reversi, Terminal and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only modal dialog boxes may appear over other windows. Microsoft sold as included Windows Development libraries with the C development environment, which included numerous windows samples. Windows 2.0 was released in December 1987, and was more popular than its predecessor. It features several improvements to the user interface and memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights. Windows 2.0 also introduced more sophisticated keyboard shortcuts and could make use of expanded memory. Windows 2.1 was released in two different versions: Windows/286 and Windows/386. Windows/386 uses the virtual 8086 mode of the Intel 80386 to multitask several DOS programs and the paged memory model to emulate expanded memory using available extended memory. Windows/286, in spite of its name, runs on both Intel 8086 and Intel 80286 processors. It runs in real mode but can make use of the high memory area. In addition to full Windows-packages, there were runtime-only versions that shipped with early Windows software from third parties and made it possible to run their Windows software on MS-DOS and without the full Windows feature set. The early versions of Windows are often thought of as graphical shells, mostly because they ran on top of MS-DOS and use it for file system services. However, even the earliest Windows versions already assumed many typical operating system functions; notably, having their own executable file format and providing their own device drivers (timer, graphics, printer, mouse, keyboard and sound). Unlike MS-DOS, Windows allowed users to execute multiple graphical applications at the same time, through cooperative multitasking. Windows implemented an elaborate, segment-based, software virtual memory scheme, which allows it to run applications larger than available memory: code segments and resources are swapped in and thrown away when memory became scarce; data segments moved in memory when a given application had relinquished processor control. Windows 3.x Windows 3.0, released in 1990, improved the design, mostly because of virtual memory and loadable virtual device drivers (VxDs) that allow Windows to share arbitrary devices between multi-tasked DOS applications. Windows 3.0 applications can run in protected mode, which gives them access to several megabytes of memory without the obligation to participate in the software virtual memory scheme. They run inside the same address space, where the segmented memory provides a degree of protection. Windows 3.0 also featured improvements to the user interface. Microsoft rewrote critical operations from C into assembly. Windows 3.0 is the first Microsoft Windows version to achieve broad commercial success, selling 2 million copies in the first six months. Windows 3.1, made generally available on March 1, 1992, featured a facelift. In August 1993, Windows for Workgroups, a special version with integrated peer-to-peer networking features and a version number of 3.11, was released. It was sold along with Windows 3.1. Support for Windows 3.1 ended on December 31, 2001. Windows 3.2, released 1994, is an updated version of the Chinese version of Windows 3.1. The update was limited to this language version, as it fixed only issues related to the complex writing system of the Chinese language. Windows 3.2 was generally sold by computer manufacturers with a ten-disk version of MS-DOS that also had Simplified Chinese characters in basic output and some translated utilities. Windows 9x The next major consumer-oriented release of Windows, Windows 95, was released on August 24, 1995. While still remaining MS-DOS-based, Windows 95 introduced support for native 32-bit applications, plug and play hardware, preemptive multitasking, long file names of up to 255 characters, and provided increased stability over its predecessors. Windows 95 also introduced a redesigned, object oriented user interface, replacing the previous Program Manager with the Start menu, taskbar, and Windows Explorer shell. Windows 95 was a major commercial success for Microsoft; Ina Fried of CNET remarked that "by the time Windows 95 was finally ushered off the market in 2001, it had become a fixture on computer desktops around the world." Microsoft published four OEM Service Releases (OSR) of Windows 95, each of which was roughly equivalent to a service pack. The first OSR of Windows 95 was also the first version of Windows to be bundled with Microsoft's web browser, Internet Explorer. Mainstream support for Windows 95 ended on December 31, 2000, and extended support for Windows 95 ended on December 31, 2001. Windows 95 was followed up with the release of Windows 98 on June 25, 1998, which introduced the Windows Driver Model, support for USB composite devices, support for ACPI, hibernation, and support for multi-monitor configurations. Windows 98 also included integration with Internet Explorer 4 through Active Desktop and other aspects of the Windows Desktop Update (a series of enhancements to the Explorer shell which were also made available for Windows 95). In May 1999, Microsoft released Windows 98 Second Edition, an updated version of Windows 98. Windows 98 SE added Internet Explorer 5.0 and Windows Media Player 6.2 amongst other upgrades. Mainstream support for Windows 98 ended on June 30, 2002, and extended support for Windows 98 ended on July 11, 2006. On September 14, 2000, Microsoft released Windows Me (Millennium Edition), the last DOS-based version of Windows. Windows Me incorporated visual interface enhancements from its Windows NT-based counterpart Windows 2000, had faster boot times than previous versions (which however, required the removal of the ability to access a real mode DOS environment, removing compatibility with some older programs), expanded multimedia functionality (including Windows Media Player 7, Windows Movie Maker, and the Windows Image Acquisition framework for retrieving images from scanners and digital cameras), additional system utilities such as System File Protection and System Restore, and updated home networking tools. However, Windows Me was faced with criticism for its speed and instability, along with hardware compatibility issues and its removal of real mode DOS support. PC World considered Windows Me to be one of the worst operating systems Microsoft had ever released, and the 4th worst tech product of all time. Windows NT Version history Early versions (Windows NT 3.1/3.5/3.51/4.0/2000) In November 1988, a new development team within Microsoft (which included former Digital Equipment Corporation developers Dave Cutler and Mark Lucovsky) began work on a revamped version of IBM and Microsoft's OS/2 operating system known as "NT OS/2". NT OS/2 was intended to be a secure, multi-user operating system with POSIX compatibility and a modular, portable kernel with preemptive multitasking and support for multiple processor architectures. However, following the successful release of Windows 3.0, the NT development team decided to rework the project to use an extended 32-bit port of the Windows API known as Win32 instead of those of OS/2. Win32 maintained a similar structure to the Windows APIs (allowing existing Windows applications to easily be ported to the platform), but also supported the capabilities of the existing NT kernel. Following its approval by Microsoft's staff, development continued on what was now Windows NT, the first 32-bit version of Windows. However, IBM objected to the changes, and ultimately continued OS/2 development on its own. Windows NT was the first Windows operating system based on a hybrid kernel. The hybrid kernel was designed as a modified microkernel, influenced by the Mach microkernel developed by Richard Rashid at Carnegie Mellon University, but without meeting all of the criteria of a pure microkernel. The first release of the resulting operating system, Windows NT 3.1 (named to associate it with Windows 3.1) was released in July 1993, with versions for desktop workstations and servers. Windows NT 3.5 was released in September 1994, focusing on performance improvements and support for Novell's NetWare, and was followed up by Windows NT 3.51 in May 1995, which included additional improvements and support for the PowerPC architecture. Windows NT 4.0 was released in June 1996, introducing the redesigned interface of Windows 95 to the NT series. On February 17, 2000, Microsoft released Windows 2000, a successor to NT 4.0. The Windows NT name was dropped at this point in order to put a greater focus on the Windows brand. Windows XP The next major version of Windows NT, Windows XP, was released on October 25, 2001. The introduction of Windows XP aimed to unify the consumer-oriented Windows 9x series with the architecture introduced by Windows NT, a change which Microsoft promised would provide better performance over its DOS-based predecessors. Windows XP would also introduce a redesigned user interface (including an updated Start menu and a "task-oriented" Windows Explorer), streamlined multimedia and networking features, Internet Explorer 6, integration with Microsoft's .NET Passport services, a "compatibility mode" to help provide backwards compatibility with software designed for previous versions of Windows, and Remote Assistance functionality. At retail, Windows XP was now marketed in two main editions: the "Home" edition was targeted towards consumers, while the "Professional" edition was targeted towards business environments and power users, and included additional security and networking features. Home and Professional were later accompanied by the "Media Center" edition (designed for home theater PCs, with an emphasis on support for DVD playback, TV tuner cards, DVR functionality, and remote controls), and the "Tablet PC" edition (designed for mobile devices meeting its specifications for a tablet computer, with support for stylus pen input and additional pen-enabled applications). Mainstream support for Windows XP ended on April 14, 2009. Extended support ended on April 8, 2014. After Windows 2000, Microsoft also changed its release schedules for server operating systems; the server counterpart of Windows XP, Windows Server 2003, was released in April 2003. It was followed in December 2005, by Windows Server 2003 R2. Windows Vista After a lengthy development process, Windows Vista was released on November 30, 2006, for volume licensing and January 30, 2007, for consumers. It contained a number of new features, from a redesigned shell and user interface to significant technical changes, with a particular focus on security features. It was available in a number of different editions, and has been subject to some criticism, such as drop of performance, longer boot time, criticism of new UAC, and stricter license agreement. Vista's server counterpart, Windows Server 2008 was released in early 2008. Windows 7 On July 22, 2009, Windows 7 and Windows Server 2008 R2 were released as RTM (release to manufacturing) while the former was released to the public 3 months later on October 22, 2009. Unlike its predecessor, Windows Vista, which introduced a large number of new features, Windows 7 was intended to be a more focused, incremental upgrade to the Windows line, with the goal of being compatible with applications and hardware with which Windows Vista was already compatible. Windows 7 has multi-touch support, a redesigned Windows shell with an updated taskbar with revealable jump lists that contain shortcuts to files frequently used with specific applications and shortcuts to tasks within the application, a home networking system called HomeGroup, and performance improvements. Windows 8 and 8.1 Windows 8, the successor to Windows 7, was released generally on October 26, 2012. A number of significant changes were made on Windows 8, including the introduction of a user interface based around Microsoft's Metro design language with optimizations for touch-based devices such as tablets and all-in-one PCs. These changes include the Start screen, which uses large tiles that are more convenient for touch interactions and allow for the display of continually updated information, and a new class of apps which are designed primarily for use on touch-based devices. The new Windows version required a minimum resolution of 1024×768 pixels, effectively making it unfit for netbooks with 800×600-pixel screens. Other changes include increased integration with cloud services and other online platforms (such as social networks and Microsoft's own OneDrive (formerly SkyDrive) and Xbox Live services), the Windows Store service for software distribution, and a new variant known as Windows RT for use on devices that utilize the ARM architecture, and a new keyboard shortcut for screenshots. An update to Windows 8, called Windows 8.1, was released on October 17, 2013, and includes features such as new live tile sizes, deeper OneDrive integration, and many other revisions. Windows 8 and Windows 8.1 have been subject to some criticism, such as removal of the Start menu. Windows 10 On September 30, 2014, Microsoft announced Windows 10 as the successor to Windows 8.1. It was released on July 29, 2015, and addresses shortcomings in the user interface first introduced with Windows 8. Changes on PC include the return of the Start Menu, a virtual desktop system, and the ability to run Windows Store apps within windows on the desktop rather than in full-screen mode. Windows 10 is said to be available to update from qualified Windows 7 with SP1, Windows 8.1 and Windows Phone 8.1 devices from the Get Windows 10 Application (for Windows 7, Windows 8.1) or Windows Update (Windows 7). In February 2017, Microsoft announced the migration of its Windows source code repository from Perforce to Git. This migration involved 3.5 million separate files in a 300 gigabyte repository. By May 2017, 90 percent of its engineering team was using Git, in about 8500 commits and 1760 Windows builds per day. In June 2021, shortly before Microsoft's announcement of Windows 11, Microsoft updated their lifecycle policy pages for Windows 10, revealing that support for their last release of Windows 10 will be October 14, 2025. Windows 11 On June 24, 2021, Windows 11 was announced as the successor to Windows 10 during a livestream. The new operating system was designed to be more user-friendly and understandable. It was released on October 5, 2021. Windows 11 is a free upgrade to some Windows 10 users as of now. Windows 365 In July 2021, Microsoft announced it will start selling subscriptions to virtualized Windows desktops as part of a new Windows 365 service in the following month. It is not a standalone version of Microsoft Windows, but a web service that provides access to Windows 10 and Windows 11 built on top of Azure Virtual Desktop. The new service will allow for cross-platform usage, aiming to make the operating system available for both Apple and Android users. The subscription-based service will be accessible through any operating system with a web browser. Microsoft has stated that the new service is an attempt at capitalizing on the growing trend, fostered during the COVID-19 pandemic, for businesses to adopt a hybrid work environment, in which "employees split their time between the office and home" according to vice president Jared Spataro. As the service will be accessible through web-browsers, Microsoft will be able to bypass the need to publish the service through Google Play or the Apple App Store. Microsoft announced Windows 365 availability to business and enterprise customers on August 2, 2021. Multilingual support Multilingual support has been built into Windows since Windows 3.0. The language for both the keyboard and the interface can be changed through the Region and Language Control Panel. Components for all supported input languages, such as Input Method Editors, are automatically installed during Windows installation (in Windows XP and earlier, files for East Asian languages, such as Chinese, and right-to-left scripts, such as Arabic, may need to be installed separately, also from the said Control Panel). Third-party IMEs may also be installed if a user feels that the provided one is insufficient for their needs. Interface languages for the operating system are free for download, but some languages are limited to certain editions of Windows. Language Interface Packs (LIPs) are redistributable and may be downloaded from Microsoft's Download Center and installed for any edition of Windows (XP or later) they translate most, but not all, of the Windows interface, and require a certain base language (the language which Windows originally shipped with). This is used for most languages in emerging markets. Full Language Packs, which translates the complete operating system, are only available for specific editions of Windows (Ultimate and Enterprise editions of Windows Vista and 7, and all editions of Windows 8, 8.1 and RT except Single Language). They do not require a specific base language, and are commonly used for more popular languages such as French or Chinese. These languages cannot be downloaded through the Download Center, but available as optional updates through the Windows Update service (except Windows 8). The interface language of installed applications is not affected by changes in the Windows interface language. The availability of languages depends on the application developers themselves. Windows 8 and Windows Server 2012 introduces a new Language Control Panel where both the interface and input languages can be simultaneously changed, and language packs, regardless of type, can be downloaded from a central location. The PC Settings app in Windows 8.1 and Windows Server 2012 R2 also includes a counterpart settings page for this. Changing the interface language also changes the language of preinstalled Windows Store apps (such as Mail, Maps and News) and certain other Microsoft-developed apps (such as Remote Desktop). The above limitations for language packs are however still in effect, except that full language packs can be installed for any edition except Single Language, which caters to emerging markets. Platform support Windows NT included support for several platforms before the x86-based personal computer became dominant in the professional world. Windows NT 4.0 and its predecessors supported PowerPC, DEC Alpha and MIPS R4000 (although some of the platforms implement 64-bit computing, the OS treated them as 32-bit). Windows 2000 dropped support for all platforms, except the third generation x86 (known as IA-32) or newer in 32-bit mode. The client line of Windows NT family still runs on IA-32 but the Windows Server line ceased supporting this platform with the release of Windows Server 2008 R2. With the introduction of the Intel Itanium architecture (IA-64), Microsoft released new versions of Windows to support it. Itanium versions of Windows XP and Windows Server 2003 were released at the same time as their mainstream x86 counterparts. Windows XP 64-Bit Edition, released in 2005, is the last Windows client operating systems to support Itanium. Windows Server line continues to support this platform until Windows Server 2012; Windows Server 2008 R2 is the last Windows operating system to support Itanium architecture. On April 25, 2005, Microsoft released Windows XP Professional x64 Edition and Windows Server 2003 x64 Editions to support x86-64 (or simply x64), the 64-bit version of x86 architecture. Windows Vista was the first client version of Windows NT to be released simultaneously in IA-32 and x64 editions. x64 is still supported. An edition of Windows 8 known as Windows RT was specifically created for computers with ARM architecture and while ARM is still used for Windows smartphones with Windows 10, tablets with Windows RT will not be updated. Starting from Windows 10 Fall Creators Update (version 1709) and later includes support for PCs with ARM architecture. Windows 11 is the first version to drop support for 32-bit hardware. Windows CE Windows CE (officially known as Windows Embedded Compact), is an edition of Windows that runs on minimalistic computers, like satellite navigation systems and some mobile phones. Windows Embedded Compact is based on its own dedicated kernel, dubbed Windows CE kernel. Microsoft licenses Windows CE to OEMs and device makers. The OEMs and device makers can modify and create their own user interfaces and experiences, while Windows CE provides the technical foundation to do so. Windows CE was used in the Dreamcast along with Sega's own proprietary OS for the console. Windows CE was the core from which Windows Mobile was derived. Its successor, Windows Phone 7, was based on components from both Windows CE 6.0 R3 and Windows CE 7.0. Windows Phone 8 however, is based on the same NT-kernel as Windows 8. Windows Embedded Compact is not to be confused with Windows XP Embedded or Windows NT 4.0 Embedded, modular editions of Windows based on Windows NT kernel. Xbox OS Xbox OS is an unofficial name given to the version of Windows that runs on Xbox consoles. From Xbox One onwards it is an implementation with an emphasis on virtualization (using Hyper-V) as it is three operating systems running at once, consisting of the core operating system, a second implemented for games and a more Windows-like environment for applications. Microsoft updates Xbox One's OS every month, and these updates can be downloaded from the Xbox Live service to the Xbox and subsequently installed, or by using offline recovery images downloaded via a PC. It was originally based on NT 6.2 (Windows 8) kernel, and the latest version runs on an NT 10.0 base. This system is sometimes referred to as "Windows 10 on Xbox One" or "OneCore". Xbox One and Xbox Series operating systems also allow limited (due to licensing restrictions and testing resources) backward compatibility with previous generation hardware, and the Xbox 360's system is backwards compatible with the original Xbox. Version control system Before 2017 Microsoft has used a proprietary SourceDepot Version Control system which couldn't keep up with size of Windows. Microsoft had begun to integrate Git into Team Foundation Server in 2013, but Windows continued to rely on Source Depot. The Windows code was divided among 65 different repositories with a kind of virtualization layer to produce unified view of all of the code. In 2017 Microsoft announced that it would start using Git, an open source version control system created by Linus Torvalds and in May 2017 they reported that has completed migration into the Git repository. VFSForGit Because of its large, decades-long history, however, the Windows codebase is not especially well suited to the decentralized nature of Linux development that Git was originally created to manage. Each Git repository contains a complete history of all the files, which proved unworkable for Windows developers because cloning the whole repository takes several hours. Microsoft has been working on a new project called the Virtual File System for Git (VFSForGit) to address these challenges. In 2021 the VFS for Git has been superseded by Scalar. Timeline of releases Usage share and device sales Use of the latest version Windows 10 has exceeded Windows 7 globally since early 2018. For desktop and laptop computers, according to Net Applications and StatCounter, which track the use of operating systems in devices that are active on the Web, Windows was the most used operating-system family in August 2021, with around 91% usage share according to Net Applications and around 76% usage share according to StatCounter. Including personal computers of all kinds (e.g., desktops, laptops, mobile devices, and game consoles), Windows OSes accounted for 32.67% of usage share in August 2021, compared to Android (highest, at 46.03%), iOS's 13.76%, iPadOS's 2.81%, and macOS's 2.51%, according to Net Applications and 30.73% of usage share in August 2021, compared to Android (highest, at 42.56%), iOS/iPadOS's 16.53%, and macOS's 6.51%, according to StatCounter. Those statistics do not include servers (including so-called cloud computing, where Microsoft is known not to be a leader, with Linux used more than Windows), as Net Applications and StatCounter use web browsing as a proxy for all use. Security Consumer versions of Windows were originally designed for ease-of-use on a single-user PC without a network connection, and did not have security features built in from the outset. However, Windows NT and its successors are designed for security (including on a network) and multi-user PCs, but were not initially designed with Internet security in mind as much, since, when it was first developed in the early 1990s, Internet use was less prevalent. These design issues combined with programming errors (e.g. buffer overflows) and the popularity of Windows means that it is a frequent target of computer worm and virus writers. In June 2005, Bruce Schneier's Counterpane Internet Security reported that it had seen over 1,000 new viruses and worms in the previous six months. In 2005, Kaspersky Lab found around 11,000 malicious programs viruses, Trojans, back-doors, and exploits written for Windows. Microsoft releases security patches through its Windows Update service approximately once a month (usually the second Tuesday of the month), although critical updates are made available at shorter intervals when necessary. In versions of Windows after and including Windows 2000 SP3 and Windows XP, updates can be automatically downloaded and installed if the user selects to do so. As a result, Service Pack 2 for Windows XP, as well as Service Pack 1 for Windows Server 2003, were installed by users more quickly than it otherwise might have been. While the Windows 9x series offered the option of having profiles for multiple users, they had no concept of access privileges, and did not allow concurrent access; and so were not true multi-user operating systems. In addition, they implemented only partial memory protection. They were accordingly widely criticised for lack of security. The Windows NT series of operating systems, by contrast, are true multi-user, and implement absolute memory protection. However, a lot of the advantages of being a true multi-user operating system were nullified by the fact that, prior to Windows Vista, the first user account created during the setup process was an administrator account, which was also the default for new accounts. Though Windows XP did have limited accounts, the majority of home users did not change to an account type with fewer rights – partially due to the number of programs which unnecessarily required administrator rights – and so most home users ran as administrator all the time. Windows Vista changes this by introducing a privilege elevation system called User Account Control. When logging in as a standard user, a logon session is created and a token containing only the most basic privileges is assigned. In this way, the new logon session is incapable of making changes that would affect the entire system. When logging in as a user in the Administrators group, two separate tokens are assigned. The first token contains all privileges typically awarded to an administrator, and the second is a restricted token similar to what a standard user would receive. User applications, including the Windows shell, are then started with the restricted token, resulting in a reduced privilege environment even under an Administrator account. When an application requests higher privileges or "Run as administrator" is clicked, UAC will prompt for confirmation and, if consent is given (including administrator credentials if the account requesting the elevation is not a member of the administrators group), start the process using the unrestricted token. Leaked documents published by WikiLeaks, codenamed Vault 7 and dated from 2013 to 2016, detail the capabilities of the CIA to perform electronic surveillance and cyber warfare, such as the ability to compromise operating systems such as Microsoft Windows. In August 2019, computer experts reported that the BlueKeep security vulnerability, , that potentially affects older unpatched Microsoft Windows versions via the program's Remote Desktop Protocol, allowing for the possibility of remote code execution, may now include related flaws, collectively named DejaBlue, affecting newer Windows versions (i.e., Windows 7 and all recent versions) as well. In addition, experts reported a Microsoft security vulnerability, , based on legacy code involving Microsoft CTF and ctfmon (ctfmon.exe), that affects all Windows versions from the older Windows XP version to the most recent Windows 10 versions; a patch to correct the flaw is currently available. File permissions All Windows versions from Windows NT 3 have been based on a file system permission system referred to as AGDLP (Accounts, Global, Domain Local, Permissions) in which file permissions are applied to the file/folder in the form of a 'local group' which then has other 'global groups' as members. These global groups then hold other groups or users depending on different Windows versions used. This system varies from other vendor products such as Linux and NetWare due to the 'static' allocation of permission being applied directly to the file or folder. However using this process of AGLP/AGDLP/AGUDLP allows a small number of static permissions to be applied and allows for easy changes to the account groups without reapplying the file permissions on the files and folders. Alternative implementations Owing to the operating system's popularity, a number of applications have been released that aim to provide compatibility with Windows applications, either as a compatibility layer for another operating system, or as a standalone system that can run software written for Windows out of the box. These include: Wine – a free and open-source implementation of the Windows API, allowing one to run many Windows applications on x86-based platforms, including UNIX, Linux and macOS. Wine developers refer to it as a "compatibility layer" and use Windows-style APIs to emulate Windows environment. CrossOver – a Wine package with licensed fonts. Its developers are regular contributors to Wine, and focus on Wine running officially supported applications. Cedega – a proprietary fork of Wine by TransGaming Technologies, designed specifically for running Microsoft Windows games on Linux. A version of Cedega known as Cider allows Windows games to run on macOS. Since Wine was licensed under the LGPL, Cedega has been unable to port the improvements made to Wine to their proprietary codebase. Cedega ceased its service in February 2011. Darwine – a port of Wine for macOS and Darwin. Operates by running Wine on QEMU. Linux Unified Kernel – a set of patches to the Linux kernel allowing many Windows executable files in Linux (using Wine DLLs); and some Windows drivers to be used. ReactOS – an open-source OS intended to run the same software as Windows, originally designed to simulate Windows NT 4.0, now aiming at Windows 7 compatibility. It has been in the development stage since 1996. Linspire – formerly LindowsOS, a commercial Linux distribution initially created with the goal of running major Windows software. Changed its name to Linspire after Microsoft v. Lindows. Discontinued in favor of Xandros Desktop, that was also later discontinued. Freedows OS – an open-source attempt at creating a Windows clone for x86 platforms, intended to be released under the GNU General Public License. Started in 1996, by Reece K. Sellin, the project was never completed, getting only to the stage of design discussions which featured a number of novel concepts until it was suspended in 2002. See also Architecture of Windows NT Azure Sphere, Microsoft's Linux-based operating system BlueKeep De facto standard Dominant design Windows Subsystem for Linux, a subsystem in Windows 10, not using the Linux kernel; reimplementing Wintel References External links Official Windows Blog Microsoft Developer Network Windows Developer Center Microsoft Windows History Timeline Pearson Education, InformIT – History of Microsoft Windows Microsoft Business Software Solutions Windows 10 release Information 1985 software Computer-related introductions in 1985 Computing platforms Microsoft franchises Personal computers Windows Operating system families Products introduced in 1985

Operating System (OS)

Glossary of operating systems terms This page is a glossary of Operating systems terminology. A access token: In Microsoft Windows operating systems, an access token contains the security credentials for a login session and identifies the user, the user's groups, the user's privileges, and, in some cases, a particular application. B binary semaphore: See semaphore. booting: In computing, booting (also known as booting up) is the initial set of operations that a computer performs after electrical power is switched on or when the computer is reset. This can take tens of seconds and typically involves performing a power-on self-test, locating and initializing peripheral devices, and then finding, loading and starting the operating system. C cache: In computer science, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere. cloud: Cloud computing operating systems are recent, and were not mentioned in Gagne's 8th Edition (2009). In contrast, by Gagne's 9th (2012), cloud o/s received 3 pages of coverage (41, 42, 716). Doeppner (2011) mentions them (p. 3), but only to prove that operating systems "are not a solved problem" and that even if the day of the dedicated PC is waning, cloud computing has created an entirely new opportunity for o/s development ala sharing, networks, memory, parallelism, etc. Gagne (2012) adds that in addition to numerous traditional o/s's at cloud warehouses, Virtual machine o/s (VMMs), Eucalyptus, Vware, vCloud Director and others are being developed specifically for cloud management with numerous traditional o/s features (security, threads, file and memory management, guis, etc.) (p. 42). Microsoft's investment in cloud aspects of o/s tend to support that argument. concurrency D daemon: Operating systems often start daemons at boot time and serve the function of responding to network requests, hardware activity, or other programs by performing some task. Daemons can also configure hardware (like udevd on some Linux systems), run scheduled tasks (like cron), and perform a variety of other tasks. E F G H I J K kernel: In computing, the kernel is a computer program that manages input/output requests from software and translates them into data processing instructions for the central processing unit and other electronic components of a computer. The kernel is a fundamental part of a modern computer's operating system. L lock: In computer science, a lock or mutex (from mutual exclusion) is a synchronization mechanism for enforcing limits on access to a resource in an environment where there are many threads of execution. A lock is designed to enforce a mutual exclusion concurrency control policy. M mutual exclusion: Mutual exclusion is to allow only one process at a time to access the same critical section (a part of code which accesses the critical resource). This helps prevent race conditions. mutex: See lock. N O P paging daemon: See daemon. process Q R S semaphore: In computer science, particularly in operating systems, a semaphore is a variable or abstract data type that is used for controlling access, by multiple processes, to a common resource in a parallel programming or a multi user environment. T thread: In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by an operating system scheduler. The scheduler itself is a light-weight process. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process. templating: In an o/s context, templating refers to creating a single virtual machine image as a guest operating system, then saving it as a tool for multiple running virtual machines (Gagne, 2012, p. 716). The technique is used both in virtualization and cloud computing management, and is common in large server warehouses. U V W Z References External links IBM's Glossary of Z/OS terms at IBM.com Operating Systems Glossary at Whatis.com Itanium architecture specification at Intel.com Linux Journalling Flash File System (JFFS) at Sourceware.org See also List of technology terms Comparison of operating systems List of important publications in operating systems List of operating systems Timeline of operating systems Operating systems Lists of computer terms

Operating System (OS)

OS/8 OS/8 was the primary operating system used on the Digital Equipment Corporation's PDP-8 minicomputer. Pre-OS/8 there were earlier PDP-8 operating systems: R-L Monitor, also referred to as MS/8. P?S/8, requiring only 4K of memory. PDP-8 4K Disk Monitor System PS/8 ("Programming System/8"), requiring 8K. This is what became OS/8 in 1971. Other/related DEC operating systems were: OS/78, OS/278, OS/12. The latter is a virtually identical version of OS/8, and was used with Digital's PDP-12 computer. Digital released OS/8 images for non-commercial purposes which can be emulated through SIMH. Overview OS/8 provided a simple operating environment that was commensurate in complexity and scale with the PDP-8 computers on which it ran. I/O was supported via a series of supplied drivers which used polled (not interrupt-driven) techniques. The device drivers had to be cleverly written as they could occupy only one or two memory pages of 128 12-bit words, and had to be able to run in any page in field 0. This often required considerable cleverness, such as the use of the OPR instruction (7XXX) for small negative constants. The memory-resident "footprint" of OS/8 was only 256 words; 128 words at the top of Field 0 and 128 words at the top of Field 1. The rest of the operating system (the USR, "User Service Routines") was swapped in and out of memory transparently (with regard to the user's program) as needed. The Concise Command Language Early versions of OS/8 had a very rudimentary command-line interpreter with very few basic commands: GET, SAVE, RUN, ASSIGN, DEASSIGN, and ODT. With version 3 they added a more sophisticated overlay called CCL (Concise Command Language) that implemented many more commands. OS/8's CCL was directly patterned after the CCL found on Digital's PDP-10 systems running TOPS-10. In fact, much of the OS/8 software system was deliberately designed to mimic, as closely as possible, the TOPS-10 operating environment. (The CCL command language was later used on PDP-11 computers running RT-11, RSX-11, and RSTS/E, providing a similar user operating environment across all three architectures: PDP-8s, PDP-10s, and PDP-11s.) The basic OS and CCL implemented many rather sophisticated commands, many of which still do not exist in modern command languages, not even in MS-DOS, Windows, or Unix-like operating systems. For example, the COMPILE command would automatically find the right compiler for a given source file and start the compile/assemble/link cycle. The ASSIGN and DEASSIGN commands allowed one to use logical device names in a program instead of physical names (as required in MS-DOS). For example, your program could write to device FLOP:AAA.TXT, and if you first did an "ASSIGN FLOP: RXA2:" then the file would be created on physical device RXA2 (the second floppy disk drive). VAX/VMS and the Commodore Amiga's operating system AmigaOS (and other OSes built around Tripos) made considerable use of this very flexible feature. The SET command was capable of setting many system options, albeit by the crude method of patching locations in the system binary code. One of them, a command under OS-78, was SET SYS OS8, and it re-enabled the MONITOR commands that were not part of OS-78. The BUILD command could reconfigure the OS on the fly, even adding device drivers, often without having to reboot the OS. The OS can boot from a hard disk and present the command prompt in under half a second. The OS/8 Filesystem OS/8 supported a simple, flat file system on a variety of mass storage devices including: TU56 DECtapes DF32 32KW fixed-head disks RF08 256KW fixed-head disks RK01/02/03/04/05 cartridge disk drives RL01/02 cartridge disk drives RX01/02 floppy diskette drives Filenames on the PDP-8 took the form of FFFFFF.XX where "F" represents an uppercase, alphanumeric character of the filename and "X" represents an upper-case, alphanumeric character of the extension (filetype). .PA : Assembly language .SV : saved core-images (executable programs) .FT : Fortran source files .DA : Data files The contents of any given file was stored contiguously in a single "extent". PIP included an option to compress ("squeeze") the filesystem, so that all unallocated space was moved to a single extent at the end of the disk. This could be invoked by the SQuish CCL command, much as MUNG could be used to run a TECO macro. OS/8 volumes had a very limited maximum storage size (4096 blocks of 256 12-bit words) and the RK05 (2.4MB) moving-head disk exceeded this size: "1.6 million words of storage." Because of this, RK05 cartridges were divided into two partitions. For example, the first RK05 on a system would be known as both RKA0: (SY:) and RKB0:. This division was commonly thought to mean "the upper surface" and "the lower surface" but this was incorrect; it in fact was "the outer cylinders" and "the inner cylinders". ASCII files ASCII files were stored as 3 8-bit characters per pair of 12-bit words: Characters 1 & 2 on the right of words 1 & 2, with bits 0-3 & 4-7 of the 3rd character stored in the leftmost bits of the pair of words. WORD 1: c0 c1 c2 c3 | a0 a1 a2 a3 a4 a5 a6 a7 WORD 2: c4 c5 c6 c7 | b0 b1 b2 b3 b4 b5 b6 b7ASCII files end with a CTRL/Z (ASCII 232). OS/8 date format OS/8 allocated the PDP-8's 12 bit words for storing dates per: 4 bits for the month 5 bits for the date therein 3 bits for the year. Y3B! This was recognized when COS-310 was developed. OS/8 CUSPs (Utility Programs) The CUSPs (Commonly-Used System Programs, that is utilities) supplied with OS/8 included: BUILD (the program to install a configured OS/8 system onto mass storage) DIR (the directory-listing program) EDIT (A line-oriented editor) MACREL (A relocating assembler that, unlike PAL, implemented macros. Written by Stanley Rabinowitz of DEC's Small Systems Group. Stan had an ASCII-artwork picture of a fish in his office that said "MACREL IS A FISH") FLAP (An absolute assembler derived from RALF) FORTRAN-II. FOTP (File-Oriented Transfer Program, an alternative to PIP) PAL (The assembler) PIP (the Peripheral Interchange Program, used to copy files) PIP10 (a version of PIP used to copy files to from PDP-10 DECtapes) RALF (Another relocating assembler for the FPP) TECO (Text Editor and COrrector, a much-more-sophisticated editor). The MUNG command ran TECO macros. CCL, the command line interpreter, was supplied in source form and could be extended by the user. Programming languages BASIC A single-user BASIC and two multi-user versions of BASIC were available as options. The single-user BASIC used several overlays to provide the full functionality of the language; when OS/8 was booted from a DECtape, a very noticeable delay occurred each time BASIC was required to switch overlays as they needed to be read from tape. The multi-user versions of BASIC (EDU20 and EDU25) differed only in whether or not they supported block-replaceable devices (DECtape or disk). Due to cost constraints, many PDP-8s had punched paper tape readers as their only mass-storage I/O device. EDU20 loaded from paper tape and could do output to a paper tape writer if the machine had one, whereas EDU25 understood the structure of a filesystem, could load from DECtape or disk, and could create files on DECtape or disk. Both could run multiple BASIC programs simultaneously using a primitive task-scheduler that round-robined among the attached terminals. Memory was always very tight because the PDP-8 used core memory, which was extremely expensive compared to RAM technology which came along a few years later. In a mere 8K of 12-bit words EDU20 could support up to 4 terminals at once, although more memory was recommended. EDU25 required an additional 4K memory bank (for a minimum of 12K) because the code contained a disk device driver and a filesystem handler. While running, EDU20 and EDU25 were self-contained programs that didn't use any OS/8 system calls. Immediately upon being invoked from the OS/8 command interpreter they would overwrite OS/8's entire resident portion - all 256 words of it. Upon startup, EDU25 would save the contents of memory to DECtape or disk and restore it when it exited. But EDU20 could not do this as it was targeted at hardware configurations without any block-replaceable device. FORTRAN In addition to a freely available FORTRAN II compiler, there was also a rather complete FORTRAN IV compiler available at extra cost. This compiler generated code for the optional FPP-8 floating-point processor, which was essentially a separate CPU, only sharing memory with the PDP-8 CPU. If you had the FPP-8 option installed, the FORTRAN runtime code would detect it and use the FPP-8 to run the main program code, and the PDP-8 CPU would run as an I/O processor. If you did not have the FPP-8, the runtime code would instead call an FPP-8 interpreter running on the PDP-8 CPU, so the program would still run, but at considerably reduced speed. This FORTRAN IV compiler in version 1 had the interesting bug that DO loops counted incorrectly: DO loops would count 1,2,3,5,6,7,… (skipping 4). A quick patch was released to fix this. See also Multics Unix TSS-8 References External links SIMH Software Kits including an OS/8 image. OS/8 Manuals at Bitsavers. Links to DEC's Hobbyist License & documentation DEC operating systems 1971 software

Operating System (OS)

Comparison of operating systems These tables provide a comparison of operating systems, of computer devices, as listing general and technical information for a number of widely used and currently available PC or handheld (including smartphone and tablet computer) operating systems. The article "Usage share of operating systems" provides a broader, and more general, comparison of operating systems that includes servers, mainframes and supercomputers. Because of the large number and variety of available Linux distributions, they are all grouped under a single entry; see comparison of Linux distributions for a detailed comparison. There is also a variety of BSD and DOS operating systems, covered in comparison of BSD operating systems and comparison of DOS operating systems. For information on views of each operating system, see operating system advocacy. General information Technical information Security Commands For POSIX compliant (or partly compliant) systems like FreeBSD, Linux, macOS or Solaris, the basic commands are the same because they are standardized. NOTE: Linux systems may vary by distribution which specific program, or even 'command' is called, via the POSIX function. For example, if you wanted to use the DOS to give you a directory listing with one detailed file listing per line you could use (e.g. in a session configuration file). See also Comparison of command shells Comparison of file systems List of operating systems Light-weight Linux distribution Operating system advocacy Security-focused operating system Timeline of operating systems Usage share of operating systems Operating system comparisons Comparison of BSD operating systems Comparison of DOS operating systems Comparison of IPv6 support in operating systems Comparison of operating system kernels Comparison of Linux distributions Comparison of netbook-oriented Linux distributions Comparison of Microsoft Windows versions Comparison of mobile operating systems Comparison of open-source operating systems Comparison of real-time operating systems Comparison of OpenSolaris distributions Comparison of Windows Vista and Windows XP References External links Comparison of operating systems Comparisons

Operating System (OS)

History of operating systems Computer operating systems (OSes) provide a set of functions needed and used by most application programs on a computer, and the links needed to control and synchronize computer hardware. On the first computers, with no operating system, every program needed the full hardware specification to run correctly and perform standard tasks, and its own drivers for peripheral devices like printers and punched paper card readers. The growing complexity of hardware and application programs eventually made operating systems a necessity for everyday use. Background The earliest computers were mainframes that lacked any form of operating system. Each user had sole use of the machine for a scheduled period of time and would arrive at the computer with program and data, often on punched paper cards and magnetic or paper tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a control panel using dials, toggle switches and panel lights. Symbolic languages, assemblers, and compilers were developed for programmers to translate symbolic program-code into machine code that previously would have been hand-encoded. Later machines came with libraries of support code on punched cards or magnetic tape, which would be linked to the user's program to assist in operations such as input and output. This was the genesis of the modern-day operating system; however, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a washing line from which tapes were hung with different colored clothes-pegs to indicate job-priority. As machines became more powerful the time to run programs diminished, and the time to hand off the equipment to the next user became large by comparison. Accounting for and paying for machine usage moved on from checking the wall clock to automatic logging by the computer. Run queues evolved from a literal queue of people at the door, to a heap of media on a jobs-waiting table, or batches of punch-cards stacked one on top of the other in the reader, until the machine itself was able to select and sequence which magnetic tape drives processed which tapes. Where program developers had originally had access to run their own jobs on the machine, they were supplanted by dedicated machine operators who looked after the machine and were less and less concerned with implementing tasks manually. When commercially available computer centers were faced with the implications of data lost through tampering or operational errors, equipment vendors were put under pressure to enhance the runtime libraries to prevent misuse of system resources. Automated monitoring was needed not just for CPU usage but for counting pages printed, cards punched, cards read, disk storage used and for signaling when operator intervention was required by jobs such as changing magnetic tapes and paper forms. Security features were added to operating systems to record audit trails of which programs were accessing which files and to prevent access to a production payroll file by an engineering program, for example. All these features were building up towards the repertoire of a fully capable operating system. Eventually the runtime libraries became an amalgamated program that was started before the first customer job and could read in the customer job, control its execution, record its usage, reassign hardware resources after the job ended, and immediately go on to process the next job. These resident background programs, capable of managing multi step processes, were often called monitors or monitor-programs before the term "operating system" established itself. An underlying program offering basic hardware-management, software-scheduling and resource-monitoring may seem a remote ancestor to the user-oriented OSes of the personal computing era. But there has been a shift in the meaning of OS. Just as early automobiles lacked speedometers, radios, and air-conditioners which later became standard, more and more optional software features became standard features in every OS package, although some applications such as database management systems and spreadsheets remain optional and separately priced. This has led to the perception of an OS as a complete user-system with an integrated graphical user interface, utilities, some applications such as text editors and file managers, and configuration tools. The true descendant of the early operating systems is what is now called the "kernel". In technical and development circles the old restricted sense of an OS persists because of the continued active development of embedded operating systems for all kinds of devices with a data-processing component, from hand-held gadgets up to industrial robots and real-time control-systems, which do not run user applications at the front-end. An embedded OS in a device today is not so far removed as one might think from its ancestor of the 1950s. The broader categories of systems and application software are discussed in the computer software article. Mainframes The first operating system used for real work was GM-NAA I/O, produced in 1956 by General Motors' Research division for its IBM 704. Most other early operating systems for IBM mainframes were also produced by customers. Early operating systems were very diverse, with each vendor or customer producing one or more operating systems specific to their particular mainframe computer. Every operating system, even from the same vendor, could have radically different models of commands, operating procedures, and such facilities as debugging aids. Typically, each time the manufacturer brought out a new machine, there would be a new operating system, and most applications would have to be manually adjusted, recompiled, and retested. Systems on IBM hardware The state of affairs continued until the 1960s when IBM, already a leading hardware vendor, stopped work on existing systems and put all its effort into developing the System/360 series of machines, all of which used the same instruction and input/output architecture. IBM intended to develop a single operating system for the new hardware, the OS/360. The problems encountered in the development of the OS/360 are legendary, and are described by Fred Brooks in The Mythical Man-Month—a book that has become a classic of software engineering. Because of performance differences across the hardware range and delays with software development, a whole family of operating systems was introduced instead of a single OS/360. IBM wound up releasing a series of stop-gaps followed by two longer-lived operating systems: OS/360 for mid-range and large systems. This was available in three system generation options: PCP for early users and for those without the resources for multiprogramming. MFT for mid-range systems, replaced by MFT-II in OS/360 Release 15/16. This had one successor, OS/VS1, which was discontinued in the 1980s. MVT for large systems. This was similar in most ways to PCP and MFT (most programs could be ported among the three without being re-compiled), but has more sophisticated memory management and a time-sharing facility, TSO. MVT had several successors including the current z/OS. DOS/360 for small System/360 models had several successors including the current z/VSE. It was significantly different from OS/360. IBM maintained full compatibility with the past, so that programs developed in the sixties can still run under z/VSE (if developed for DOS/360) or z/OS (if developed for MFT or MVT) with no change. IBM also developed TSS/360, a time-sharing system for the System/360 Model 67. Overcompensating for their perceived importance of developing a timeshare system, they set hundreds of developers to work on the project. Early releases of TSS were slow and unreliable; by the time TSS had acceptable performance and reliability, IBM wanted its TSS users to migrate to OS/360 and OS/VS2; while IBM offered a TSS/370 PRPQ, they dropped it after 3 releases. Several operating systems for the IBM S/360 and S/370 architectures were developed by third parties, including the Michigan Terminal System (MTS) and MUSIC/SP. Other mainframe operating systems Control Data Corporation developed the SCOPE operating systems in the 1960s, for batch processing and later developed the MACE operating system for time sharing, which was the basis for the later Kronos. In cooperation with the University of Minnesota, the Kronos and later the NOS operating systems were developed during the 1970s, which supported simultaneous batch and time sharing use. Like many commercial time sharing systems, its interface was an extension of the DTSS time sharing system, one of the pioneering efforts in timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the PLATO system, which used plasma panel displays and long-distance time sharing networks. PLATO was remarkably innovative for its time; the shared memory model of PLATO's TUTOR programming language allowed applications such as real-time chat and multi-user graphical games. For the UNIVAC 1107, UNIVAC, the first commercial computer manufacturer, produced the EXEC I operating system, and Computer Sciences Corporation developed the EXEC II operating system and delivered it to UNIVAC. EXEC II was ported to the UNIVAC 1108. Later, UNIVAC developed the EXEC 8 operating system for the 1108; it was the basis for operating systems for later members of the family. Like all early mainframe systems, EXEC I and EXEC II were a batch-oriented system that managed magnetic drums, disks, card readers and line printers; EXEC 8 supported both batch processing and on-line transaction processing. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BASIC system. Burroughs Corporation introduced the B5000 in 1961 with the MCP (Master Control Program) operating system. The B5000 was a stack machine designed to exclusively support high-level languages, with no software, not even at the lowest level of the operating system, being written directly in machine language or assembly language; the MCP was the first OS to be written entirely in a high-level language - ESPOL, a dialect of ALGOL 60 - although ESPOL had specialized statements for each "syllable" in the B5000 instruction set. MCP also introduced many other ground-breaking innovations, such as being one of the first commercial implementations of virtual memory. The rewrite of MCP for the B6500 is still in use today in the Unisys ClearPath/MCP line of computers. GE introduced the GE-600 series with the General Electric Comprehensive Operating Supervisor (GECOS) operating system in 1962. After Honeywell acquired GE's computer business, it was renamed to General Comprehensive Operating System (GCOS). Honeywell expanded the use of the GCOS name to cover all its operating systems in the 1970s, though many of its computers had nothing in common with the earlier GE 600 series and their operating systems were not derived from the original GECOS. Project MAC at MIT, working with GE and Bell Labs, developed Multics, which introduced the concept of ringed security privilege levels. Digital Equipment Corporation developed TOPS-10 for its PDP-10 line of 36-bit computers in 1967. Before the widespread use of Unix, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community. Bolt, Beranek, and Newman developed TENEX for a modified PDP-10 that supported demand paging; this was another popular system in the research and ARPANET communities, and was later developed by DEC into TOPS-20. Scientific Data Systems/Xerox Data Systems developed several operating systems for the Sigma series of computers, such as the Basic Control Monitor (BCM), Batch Processing Monitor (BPM), and Basic Time-Sharing Monitor (BTM). Later, BPM and BTM were succeeded by the Universal Time-Sharing System (UTS); it was designed to provide multi-programming services for online (interactive) user programs in addition to batch-mode production jobs, It was succeeded by the CP-V operating system, which combined UTS with the heavily batch-oriented Xerox Operating System. Minicomputers Digital Equipment Corporation created several operating systems for its 16-bit PDP-11 machines, including the simple RT-11 system, the time-sharing RSTS operating systems, and the RSX-11 family of real-time operating systems, as well as the VMS system for the 32-bit VAX machines. Several competitors of Digital Equipment Corporation such as Data General, Hewlett-Packard, and Computer Automation created their own operating systems. One such, "MAX III", was developed for Modular Computer Systems Modcomp II and Modcomp III computers. It was characterised by its target market being the industrial control market. The Fortran libraries included one that enabled access to measurement and control devices. IBM's key innovation in operating systems in this class (which they call "mid-range"), was their "CPF" for the System/38. This had capability-based addressing, used a machine interface architecture to isolate the application software and most of the operating system from hardware dependencies (including even such details as address size and register size) and included an integrated RDBMS. The succeeding OS/400 (now known as IBM i) for the IBM AS/400 and later IBM Power Systems has no files, only objects of different types and these objects persist in very large, flat virtual memory, called a single-level store. The Unix operating system was developed at AT&T Bell Laboratories in the late 1960s, originally for the PDP-7, and later for the PDP-11. Because it was essentially free in early editions, easily obtainable, and easily modified, it achieved wide acceptance. It also became a requirement within the Bell systems operating companies. Since it was written in the C language, when that language was ported to a new machine architecture, Unix was also able to be ported. This portability permitted it to become the choice for a second generation of minicomputers and the first generation of workstations, and its use became widespread. Unix exemplified the idea of an operating system that was conceptually the same across various hardware platforms. Because of its utility, it inspired many and later became one of the roots of the free software movement and open-source software. Numerous operating systems were based upon it including Minix, GNU/Linux, and the Berkeley Software Distribution. Apple's macOS is also based on Unix via NeXTSTEP and FreeBSD. The Pick operating system was another operating system available on a wide variety of hardware brands. Commercially released in 1973 its core was a BASIC-like language called Data/BASIC and a SQL-style database manipulation language called ENGLISH. Licensed to a large variety of manufacturers and vendors, by the early 1980s observers saw the Pick operating system as a strong competitor to Unix. Microcomputers Beginning in the mid-1970s, a new class of small computers came onto the marketplace. Featuring 8-bit processors, typically the MOS Technology 6502, Intel 8080, Motorola 6800 or the Zilog Z80, along with rudimentary input and output interfaces and as much RAM as practical, these systems started out as kit-based hobbyist computers but soon evolved into an essential business tool. Home computers While many eight-bit home computers of the 1980s, such as the BBC Micro, Commodore 64, Apple II series, the Atari 8-bit, the Amstrad CPC, ZX Spectrum series and others could load a third-party disk-loading operating system, such as CP/M or GEOS, they were generally used without one. Their built-in operating systems were designed in an era when floppy disk drives were very expensive and not expected to be used by most users, so the standard storage device on most was a tape drive using standard compact cassettes. Most, if not all, of these computers shipped with a built-in BASIC interpreter on ROM, which also served as a crude command line interface, allowing the user to load a separate disk operating system to perform file management commands and load and save to disk. The most popular home computer, the Commodore 64, was a notable exception, as its DOS was on ROM in the disk drive hardware, and the drive was addressed identically to printers, modems, and other external devices. Furthermore, those systems shipped with minimal amounts of computer memory—4-8 kilobytes was standard on early home computers—as well as 8-bit processors without specialized support circuitry like an MMU or even a dedicated real-time clock. On this hardware, a complex operating system's overhead supporting multiple tasks and users would likely compromise the performance of the machine without really being needed. As those systems were largely sold complete, with a fixed hardware configuration, there was also no need for an operating system to provide drivers for a wide range of hardware to abstract away differences. Video games and even the available spreadsheet, database and word processors for home computers were mostly self-contained programs that took over the machine completely. Although integrated software existed for these computers, they usually lacked features compared to their standalone equivalents, largely due to memory limitations. Data exchange was mostly performed through standard formats like ASCII text or CSV, or through specialized file conversion programs. Operating systems in video games and consoles Since virtually all video game consoles and arcade cabinets designed and built after 1980 were true digital machines based on microprocessors (unlike the earlier Pong clones and derivatives), some of them carried a minimal form of BIOS or built-in game, such as the ColecoVision, the Sega Master System and the SNK Neo Geo. Modern-day game consoles and videogames, starting with the PC-Engine, all have a minimal BIOS that also provides some interactive utilities such as memory card management, audio or video CD playback, copy protection and sometimes carry libraries for developers to use etc. Few of these cases, however, would qualify as a true operating system. The most notable exceptions are probably the Dreamcast game console which includes a minimal BIOS, like the PlayStation, but can load the Windows CE operating system from the game disk allowing easily porting of games from the PC world, and the Xbox game console, which is little more than a disguised Intel-based PC running a secret, modified version of Microsoft Windows in the background. Furthermore, there are Linux versions that will run on a Dreamcast and later game consoles as well. Long before that, Sony had released a kind of development kit called the Net Yaroze for its first PlayStation platform, which provided a series of programming and developing tools to be used with a normal PC and a specially modified "Black PlayStation" that could be interfaced with a PC and download programs from it. These operations require in general a functional OS on both platforms involved. In general, it can be said that videogame consoles and arcade coin-operated machines used at most a built-in BIOS during the 1970s, 1980s and most of the 1990s, while from the PlayStation era and beyond they started getting more and more sophisticated, to the point of requiring a generic or custom-built OS for aiding in development and expandability. Personal computer era The development of microprocessors made inexpensive computing available for the small business and hobbyist, which in turn led to the widespread use of interchangeable hardware components using a common interconnection (such as the S-100, SS-50, Apple II, ISA, and PCI buses), and an increasing need for "standard" operating systems to control them. The most important of the early OSes on these machines was Digital Research's CP/M-80 for the 8080 / 8085 / Z-80 CPUs. It was based on several Digital Equipment Corporation operating systems, mostly for the PDP-11 architecture. Microsoft's first operating system, MDOS/MIDAS, was designed along many of the PDP-11 features, but for microprocessor based systems. MS-DOS, or PC DOS when supplied by IBM, was designed to be similar to CP/M-80. Each of these machines had a small boot program in ROM which loaded the OS itself from disk. The BIOS on the IBM-PC class machines was an extension of this idea and has accreted more features and functions in the 20 years since the first IBM-PC was introduced in 1981. The decreasing cost of display equipment and processors made it practical to provide graphical user interfaces for many operating systems, such as the generic X Window System that is provided with many Unix systems, or other graphical systems such as Apple's classic Mac OS and macOS, the Radio Shack Color Computer's OS-9 Level II/MultiVue, Commodore's AmigaOS, Atari TOS, IBM's OS/2, and Microsoft Windows. The original GUI was developed on the Xerox Alto computer system at Xerox Palo Alto Research Center in the early 1970s and commercialized by many vendors throughout the 1980s and 1990s. Since the late 1990s, there have been three operating systems in widespread use on personal computers: Apple Inc.'s macOS, the open source Linux, and Microsoft Windows. Since 2005 and the Mac transition to Intel processors, all have been developed mainly on the x86 platform, although macOS retained PowerPC support until 2009 and Linux remains ported to a multitude of architectures including ones such as 68k, PA-RISC, and DEC Alpha, which have been long superseded and out of production, and SPARC and MIPS, which are used in servers or embedded systems but no longer for desktop computers. Other operating systems such as AmigaOS and OS/2 remain in use, if at all, mainly by retrocomputing enthusiasts or for specialized embedded applications. Mobile operating systems In the early 1990s, Psion released the Psion Series 3 PDA, a small mobile computing device. It supported user-written applications running on an operating system called EPOC. Later versions of EPOC became Symbian, an operating system used for mobile phones from Nokia, Ericsson, Sony Ericsson, Motorola, Samsung and phones developed for NTT Docomo by Sharp, Fujitsu & Mitsubishi. Symbian was the world's most widely used smartphone operating system until 2010 with a peak market share of 74% in 2006. In 1996, Palm Computing released the Pilot 1000 and Pilot 5000, running Palm OS. Microsoft Windows CE was the base for Pocket PC 2000, renamed Windows Mobile in 2003, which at its peak in 2007 was the most common operating system for smartphones in the U.S. In 2007, Apple introduced the iPhone and its operating system, known as simply iPhone OS (until the release of iOS 4), which, like Mac OS X, is based on the Unix-like Darwin. In addition to these underpinnings, it also introduced a powerful and innovative graphic user interface that was later also used on the tablet computer iPad. A year later, Android, with its own graphical user interface, was introduced, based on a modified Linux kernel, and Microsoft re-entered the mobile operating system market with Windows Phone in 2010, which was replaced by Windows 10 Mobile in 2015. In addition to these, a wide range of other mobile operating systems are contending in this area. Rise of virtualization Operating systems originally ran directly on the hardware itself and provided services to applications, but with virtualization, the operating system itself runs under the control of a hypervisor, instead of being in direct control of the hardware. On mainframes IBM introduced the notion of a virtual machine in 1968 with CP/CMS on the IBM System/360 Model 67, and extended this later in 1972 with Virtual Machine Facility/370 (VM/370) on System/370. On x86-based personal computers, VMware popularized this technology with their 1999 product, VMware Workstation, and their 2001 VMware GSX Server and VMware ESX Server products. Later, a wide range of products from others, including Xen, KVM and Hyper-V meant that by 2010 it was reported that more than 80 percent of enterprises had a virtualization program or project in place, and that 25 percent of all server workloads would be in a virtual machine. Over time, the line between virtual machines, monitors, and operating systems was blurred: Hypervisors grew more complex, gaining their own application programming interface, memory management or file system. Virtualization becomes a key feature of operating systems, as exemplified by KVM and LXC in Linux, Hyper-V in Windows Server 2008 or HP Integrity Virtual Machines in HP-UX. In some systems, such as POWER5 and POWER6-based servers from IBM, the hypervisor is no longer optional. Radically simplified operating systems, such as CoreOS have been designed to run only on virtual systems. Applications have been re-designed to run directly on a virtual machine monitor. In many ways, virtual machine software today plays the role formerly held by the operating system, including managing the hardware resources (processor, memory, I/O devices), applying scheduling policies, or allowing system administrators to manage the system. See also Charles Babbage Institute IT History Society List of operating systems Timeline of operating systems History of computer icons Notes References Further reading Operating systems History History of computing

Operating System (OS)

OS/360 and successors OS/360, officially known as IBM System/360 Operating System, is a discontinued batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was influenced by the earlier IBSYS/IBJOB and Input/Output Control System (IOCS) packages for the IBM 7090/7094 and even more so by the PR155 Operating System for the IBM 1410/7010 processors. It was one of the earliest operating systems to require the computer hardware to include at least one direct access storage device. Although OS/360 itself was discontinued, successor operating systems, including the virtual storage MVS and the 64-bit z/OS, are still run and maintain application-level compatibility. Overview IBM announced three different levels of OS/360, generated from the same tapes and sharing most of their code. IBM eventually renamed these options and made some significant design changes: Single Sequential Scheduler (SSS) Option 1 Primary Control Program (PCP) Multiple Sequential Schedulers (MSS) Option 2 Multiprogramming with a Fixed number of Tasks (MFT) MFT II Multiple Priority Schedulers (MPS) Option 4 VMS Multiprogramming with a Variable number of Tasks (MVT) Model 65 Multiprocessing (M65MP) Users often coined nicknames, e.g., "Big OS", "OS/MFT", but none of these names had any official recognition by IBM. The other major operating system for System/360 hardware was DOS/360. OS/360 is in the public domain and can be downloaded freely. As well as being run on actual System/360 hardware, it can be executed on the free Hercules emulator, which runs under most UNIX and Unix-like systems including Linux, Solaris, and macOS, as well as Windows. There are OS/360 turnkey CDs that provide pregenerated OS/360 21.8 systems ready to run under Hercules. Origin IBM originally intended that System/360 should have only one batch-oriented operating system, OS/360, capable of running on machines as small as 32 KiB. It also intended to supply a separate timesharing operating system, TSS/360, for the System/360 Model 67. There are at least two accounts of why IBM eventually decided to produce other, simpler batch-oriented operating systems: because it found that the "approximately 1.5 million instructions that enable the system to operate with virtually no manual intervention" comprising OS/360 would not fit into the limited memory available on the smaller System/360 models; or because it realized that the development of OS/360 would take much longer than expected. IBM introduced a series of stop-gaps to prevent System/360 hardware sales from collapsing—first Basic Programming Support (BPS) and BOS/360 (Basic Operating System, for the smallest machines with 8K byte memories), then TOS/360 (Tape Operating System, for machines with at least 16K byte memories and only tape drives), and finally DOS/360 (Disk Operating System), which became a mainstream operating system and is the ancestor of today's widely used z/VSE. IBM released three variants of OS/360: PCP (Primary Control Program), a stop-gap which could run only one job at a time, in 1966; MFT (Multiprogramming with Fixed number of Tasks) for the mid-range machines, and MVT (Multiprogramming with Variable number of Tasks) for the top end. MFT and MVT were used until at least 1981, a decade after their successors had been launched. The division between MFT and MVT arose because of storage limitations and scheduling constraints. Initially IBM maintained that MFT and MVT were simply "two configurations of the OS/360 control program", although later IBM described them as "separate versions of OS/360". IBM originally wrote OS/360 in assembly language. Later on, IBM wrote some OS/360 code in a new language, Basic Systems Language (BSL), derived from PL/I. A large amount of the TSO code in Release 20 was written in BSL. TSS/360 was so late and unreliable that IBM canceled it, although IBM later supplied three releases of the TSS/370 PRPQ. By this time CP-67 was running well enough for IBM to offer it without warranty as a timesharing facility for a few large customers. OS/360 variants These three options offered such similar facilities that porting applications between them usually required minimal effort; the same versions of IBM Program Products, application and utility software ran on both. The text below mostly treats PCP, MFT and MVT as simply new names for the original SSS, MSS and MPS, although there were some design changes. Also, the text does not distinguish between M65MP and MVT. Officially, PCP, MFT and MVT are not separate operating systems from OS/360, they are only install-time configuration options—in today's words, three different variants of the OS Nucleus and Scheduler. However, because of quite different behavior and memory requirements, users commonly consider them de facto separate operating systems and refer to them as "early OS/360", "OS/MFT", "OS/MVT", respectively. MFT differs from MVT mainly in the way in which it manages memory: when installing MFT, customers specify in the system generation (SysGen) a fixed number of partitions, areas of memory with fixed boundaries, in which application programs can be run simultaneously. PCP Primary Control Program (PCP) was intended for machines with small memories. It is similar to MFT with one partition. Experience indicated that it was not advisable to install OS/360 on systems with less than 128 KiB of memory, although limited production use was possible on much smaller machines, such as 48 KiB of memory. IBM dropped the PCP option in the final releases of OS/360, leaving only MFT II and MVT, both of which required more memory. Also referred to as SYS=MIN in macro expansions that were system-dependent. MFT Multiprogramming with a Fixed number of Tasks (MFT) was intended to serve as a stop-gap until Multiprogramming with a Variable number of Tasks (MVT), the intended target configuration of OS/360, became available in 1967. Early versions of MVT had many problems, so the simpler MFT continued to be used for many years. After introducing new System/370 machines with virtual memory in 1972, IBM developed MFT 2 into OS/VS1, the last system of this particular line. The first version of MFT shared much of the code and architecture with PCP, and was limited to four partitions. It was very cumbersome to run multiple partitions. Many installations used Houston Automatic Spooling Priority (HASP) to mitigate the complexity. MFT Version II (MFT-II) shared much more of the Control Program and Scheduler code with MVT, and was much more flexible to run. The maximum number of partitions increased to 52. Later modifications of MFT-II added sub-tasking, so that the fixed number of tasks was no longer fixed, although the number of partitions did remain a limitation. Experience indicated that it was not advisable to install MFT on systems with less than 256 KiB of memory, which in the 1960s was quite a large amount. Also referred to as SYS=INT in macro expansions that were system-dependent. MVT Multiprogramming with a Variable number of Tasks (MVT) was the most sophisticated of three available configurations of OS/360's control program, and one of two available configurations in the final releases. MVT was intended for the largest machines in the System/360 family. Introduced in 1964, it did not become available until 1967. Early versions had many problems and the simpler MFT continued to be used for many years. Experience indicated that it was not advisable to install MVT on systems with less than 512 KiB of memory MVT treated all memory not used by the operating system as a single pool from which contiguous regions could be allocated as required by an unlimited number of simultaneous application and systems programs. This scheme was more flexible than MFT's and in principle used memory more efficiently, but was liable to fragmentation - after a while one could find that, although there was enough spare memory in total to run a program, it was divided into separate chunks none of which was large enough. System/360 lacked memory relocation hardware so memory compaction could not be used to reduce fragmentation. A facility called Rollout/Rollin could swap a running job out to secondary storage to make its memory available to another job. The rolled-out job would, however, have to be rolled-in to the original memory locations when they again became available. In 1971 the Time Sharing Option (TSO) for use with MVT was added as part of release 20.1. TSO became widely used for program development because it provided an editor, the ability to submit batch jobs, be notified of their completion, and view the results without waiting for printed reports, and debuggers for some of the programming languages used on System/360. TSO in OS/360 communicated with terminals by using Telecommunications Access Method (TCAM). TCAM's name suggests that IBM hoped it would become the standard access method for data communications, but in fact TCAM in OS/VS2 was used almost entirely for TSO and was largely superseded by Virtual Telecommunications Access Method (VTAM) in the mid-to-late 1970s. Also referred to as SYS=VMS in invocations of some macros that were system-dependent. M65MP Model 65 Multiprocessing (M65MP) is a variant of MVT. It runs on a 360/65 in Multisystem mode M65MP traps use of the Set System Mask (SSM) instruction to serialize disabled code between the two CPUs. For the most part an M65MP system has the same behavior and interfaces as any other MVT system. The keyword parameter SYS=VMS included M65MP as well as uniprocessor MVT. Shared features PCP, MFT and MVT provide similar facilities from the point of view of application programs: The same application programming interface (API) and application binary interface (ABI), so application programs can be transferred between MFT and MVT without even needing to be modified or re-assembled or re-compiled. The same JCL (Job Control Language, for initiating batch jobs), which was more flexible and easier to use, though more complex, than that of DOS/360. The same facilities (access methods) for reading and writing files and for data communications: Sequential data sets are normally read or written one record at a time from beginning to end, using BSAM or QSAM. This was the only technique that could be used for tape drives, card readers / punches and printers. In indexed (ISAM) files a specified section of each record is defined as a key which can be used to look up specific records. In direct access (BDAM) files, the application program has to specify the relative block number, the relative track and record (TTR) or the actual physical location (MBBCCHHR) in a Direct-access storage device (DASD) of the data it wanted to access, or the starting point for a search by key. BDAM programming was not easy and most organizations never used it themselves; but it was the fastest way to access data on disks and many software companies used it in their products, especially database management systems such as ADABAS, IDMS and IBM's DL/I. It is also available from OS/360 Fortran. BDAM datasets are unblocked, with one logical record per physical record. An additional file structure, partitioned, and access method (BPAM), is mainly used for managing program libraries. Although partitioned files need to be compressed to reclaim free space, this has less impact than did a similar requirement for DOS/360's Core Image Library, because MFT and MVT allow multiple partitioned datasets and each project generally has at least one. Generation Data Groups (GDGs) were originally designed to support grandfather-father-son backup procedures - if a file was modified, the changed version became the new son, the previous son became the father, the previous father became the grandfather and the previous grandfather was deleted. But one could set up GDGs with more than 3 generations, and some applications used GDGs to collect data from large and variable numbers of sources and feed the information to one program - each collecting program created a new generation of the file and the final program read the whole group as a single sequential file (by not specifying a generation in the JCL). BTAM, a data communications facility, was primitive and hard to use by today's standards. However, it could communicate with almost any type of terminal, which was a big advantage at a time when there was hardly any standardization of communications protocols. The file naming system allows files to be managed as hierarchies with at most 8 character names at each level, e.g. PROJECT.USER.FILENAME. This is tied to the implementation of the system catalog (SYSCTLG) and Control Volumes (CVOLs), which used records with 8 byte keys. Shared features excluding PCP Some features were available only for MFT and MVT: A SPOOLing facility for MFT II and MVT (which DOS/360 initially lacked, but was, later, provided by the POWER application). Applications in MFT (Release 19 and later) and MVT could create sub-tasks, which allowed multitasking (multithreading) within the one job. Graphic Job Processing Satellite Graphic Job Processing Remote Job Entry Queued Telecommunications Access Method (QTAM) Telecommunications Access Method (TCAM) System/370 and virtual memory operating systems When System/370 was announced in 1970 it offered essentially the same facilities as System/360 but with about 4 times the processor speeds of similarly priced System/360 CPUs. Then in 1972 IBM announced System/370 Advanced Functions, of which the main item was that future sales of System/370 would include virtual memory capability and this could also be retro-fitted to existing System/370 CPUs. Hence IBM also committed to delivering enhanced operating systems which could support the use of virtual memory. OS/360 IBM provided an OS/360 SYSGEN option for S/370 support, which did not support DAT but did: Support control registers Support enhanced I/O Provide a S/370 Machine Check Handler Provide limited support for the new timer facilities OS/VS1 OS/VS1 is the successor to MFT, and offers similar facilities with several additions, e.g., RES, virtual memory. VSAM (see below) was initially available as an independent component release (ICR) and later integrated into the OS/VS1 base. IBM released fairly minor enhancements of OS/VS1 until 1983, and in 1984 announced that there would be no more. AIX/370, AIX/ESA, DPPX, IX/370, OS/VS1 and TSS/370 are the only System/370 operating systems that do not have modern descendants. OS/VS2 SVS and MVS OS/VS2 release 1 was just MVT plus virtual memory and VSAM (see below). This version was eventually renamed OS/VS2 SVS, for Single Virtual Storage, when OS/VS2 Release 2, also known as MVS, for Multiple Virtual Storage, was introduced. SVS was intended as a stepping stone from MVT to MVS, and is only of historical interest today. In 1974 IBM released what it described as OS/VS2 Release 2 but which was really a new operating system that was upwards-compatible with OS/VS2 Release 1. The Supervisor of the new system had been largely rewritten in a new dialect of BSL, PL/S; BSL and PL/S were dialects of PL/I with extensions designed to transcribe Assembly language code, including privileged instructions needed to control the computer as a whole. Time-sensitive OS components, such as the OS Dispatcher and the IOS, notably, among many others, remained coded in Assembly Language, which had been enhanced for OS/VS in the IFOX00 Assembler (from the older, OS/360 IEUASM Assembler). The new version's most noticeable feature was that it supported multiple virtual address spaces - different applications thought they were using the same range of virtual addresses, but the new system's virtual memory facilities mapped these to different ranges of real memory addresses. Each application's address space consists of 3 areas: operating system (one instance shared by all jobs); an application area which was unique for each application; shared virtual area used for various purposes including inter-job communication. IBM promised that the application areas would always be at least 8MB. This approach eliminated the risk of memory fragmentation that was present in MVT and SVS, and improved the system's internal security. The new system rapidly became known as "MVS" (Multiple Virtual Storages), the original OS/VS2 became known as "SVS" (Single Virtual Storage) and IBM itself accepted this terminology and labelled MVS's successors "MVS/xxx". MVS introduced a new approach to workload management, allowing users to define performance targets for high-priority batch jobs. This enabled users to give their systems more work than before without affecting the performance of the highest-priority jobs. MVS was IBM's first mainstream operating system on the System/370 to support what IBM called tightly coupled multiprocessing, in which 2 (later, up to 12, for IBM mainframes, and up to 16, for Amdahl mainframes) CPUs shared concurrent access to the same memory (and a single copy of the operating system and peripheral devices), providing greater processing power and a degree of graceful degradation if one CPU failed (which, fortunately, became an increasingly rare event, as system up time rose from hours to days and, then, to years.) Initially MVS was supplied with a job queue manager called JES2 (Job Entry Subsystem 2), which was descended from HASP (Houston Automatic Spooling Priority) and also supported Remote Job Entry from workstations located elsewhere. JES2 can only manage jobs for one CPU (which might be a tightly coupled multiprocessor system). In 1976 IBM provided another option, JES3 (Job Entry Subsystem 3), a descendant of ASP (Attached Support Processor), which allows one CPU to manage a single job queue feeding work to several physically distinct CPUs, and therefore allows one operator's console to manage the work of all those CPUs. Note: JES1 was the job queue manager for OS/VS1 (see above). VSAM IBM hoped that Virtual storage access method (VSAM) would replace its earlier sequential, indexed and direct access methods as it provided improved versions of these: Entry-Sequenced Datasets (ESDS) provide facilities similar to those of both sequential and BDAM (direct) datasets, since they can be read either from start to finish or directly by specifying an offset from the start. Key-Sequenced Datasets (KSDS) are a major upgrade from IBM's ISAM: they allow secondary keys with non-unique values and keys formed by concatenating non-contiguous fields in any order; they greatly reduce the performance problems caused by overflow records used to handle insertions and updates in ISAM; and they greatly reduce the risk that a software or hardware failure in the middle of an index update might corrupt the index. VSAM provides an ISAM / VSAM Interface which allows ISAM-based applications to use VSAM KSDS without reprogramming. Relative Record Datasets (RRDS) are a replacement for direct access (BDAM) datasets, allowing applications to access a record by specifying a relative record number. Unlike ESDS and KSDS, RRDS does not support variable-length records. These VSAM formats became the basis of IBM's database management systems, IMS/VS and DB2 - usually ESDS for the actual data storage and KSDS for indexes. VSAM also provides a new implementation of the catalog facility which enables applications to access files by name, without needing to know which disk drive(s) they are on. VSAM datasets must be defined in a VSAM catalog before they are used, and non-VSAM datasets can also be listed in a VSAM catalog. The MVS Master Catalog must be a VSAM catalog. Catalogs were originally provided in OS/360 in the form of CVOLs; MVS added a separate catalog structure for VSAM; later IBM added a third type of catalog known as an ICF catalog. (IBM removed support for CVOL and VSAM catalogs as of 2000, since they were not Y2K-compliant; hence in z/OS, only ICF catalogs are supported.) SNA In 1974 IBM announced Systems Network Architecture, which was meant to reduce the cost of running large networks of terminals, mainly by using communications lines much more efficiently. This is only available for IBM's virtual memory operating systems, since its mainframe software component, VTAM is only available with these operating systems. Later MVS versions and enhancements In 1977 IBM announced MVS/System Extensions, a program product (i.e., it cost extra money) which improved MVS performance and added functionality. Descendants of MVS are still used on the latest descendants of System/360, System/390 and zSeries; it was renamed to OS/390 for System/390, and the 64-bit version for the zSeries was named z/OS. Timeline These data are taken from IBM 360 Operating Systems Release History, System/370 Market Chronology of Products & Services, and IBM announcement letters. Notes References Further reading Manuals IBM, "MVT Guide" - GC28-6720-4, R21, March 1972 IBM, "MVT Supervisor PLM" - GY28-6659-7, Program Logic Manual, March 1972 IBM, "OS I/O Supervisor PLM" - GY28-6616-1, Program Logic Manual, April 1967 IBM, "OS I/O Supervisor PLM" - GY28-6616-9, Program Logic Manual, R21.7, April 1973 Books Brooks, Jr., Frederick P. (1975). "The Mythical Man-Month: Essays on Software Engineering", Addison-Wesley. . (Reprinted with corrections, January 1982) Binder, Robert V. (1985). "Application Debugging: An MVS Abend Handbook for Cobol, Assembly, PL/I, and Fortran Programmers ", Prentice-Hall. . Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and Early 370 Systems, Cambridge : MIT Press. (pp. 291–345) References in popular culture ABEND External links Operating System/360 1965–1972 MVS... A Long History on archive.org IBM mainframe operating systems Computer-related introductions in 1964 1960s software

Operating System (OS)

Optimized Systems Software Optimized Systems Software (OSS) was a company that produced disk operating systems, programming languages with integrated development environments, and applications primarily for the Atari 8-bit family of home computers. OSS was best known for their enhanced versions of Atari BASIC and the MAC/65 assembler, both of which are much faster than Atari's products, and the Action! programming language. OSS also sold some products for the Apple II. OSS transitioned to 16-bit platforms with Personal Pascal for the Atari ST and Personal Prolog for Macintosh (which was also advertised for the Atari ST, but may not have been released). OSS was not as significant in those markets. History Optimized Systems Software was formed in early 1981 by Bill Wilkinson, Mike Peters, Paul Laughton, and Kathleen O'Brien. Laughton, the primary author of Atari BASIC, was still employed by Atari, Inc. at the time, and had permission to be involved with OSS from his manager. O'Brien wrote the Atari Assembler Editor for Atari. Laughton and O'Brien (married) were not as involved with the company and were bought out by Peters and Wilkinson. OSS purchased Atari BASIC, Atari DOS, and the Atari Assembler Editor product from Shepardson Microsystems who had concluded that their BASIC and DOS products were not viable. The new company enhanced the products, renaming them OS/A+ (the Disk Operating System), BASIC A+ (a disk-based language), and EASMD (an update to the Assembler Editor). OSS continued to work with Atari (who had previously contracted with SMI) on enhanced products, most of which never reached the market. OSS debuted at the West Coast Computer Faire in March 1981. The products they released over the next several years became respected among Atari programmers, particularly the MAC/65 assembler, the Action! programming language, and BASIC XL. In a 1984 interview, Bill Wilkinson said the company consisted of 15 people. In January 1988, OSS merged with ICD (the makers of SpartaDOS and various Atari computer hardware add-ons). In 1994, Fine Tooned Engineering obtained limited rights to ICD's 8-bit products before disappearing. Disk Operating Systems OS/A+ Atari DOS 2.0S consisted of two portions, a memory-resident portion that facilitated access to disk files by programs, and a disk-resident portion providing menu-driven utilities to format, copy, delete, rename, and otherwise manipulate files on Atari's 810 disk drive. The menu system was too large to keep memory-resident, but the necessity to reload the menu system after every program was frustrating to many users. OS/A+ 2.0, 2.1 was a disk-based replacement for the Atari DOS and the Apple II DOS. It replaced the menu-driven utilities with a compact command line approach similar to CP/M (and later, MS-DOS). The command line was small enough to remain in memory with most applications, removing the need for the dreaded post-program reload. When first introduced at the West Coast Computer Faire, the program was named CP/A, but a lawyer from Digital Research (owners of CP/M) visited the booth and the name was changed. OSS couldn't have afforded even a court filing fee. OS/A+ 4.1 OSS extended the successful OS/A+ product with additional capabilities for version 4, many of which were arguably ahead of their time. For example, the strict "8.3" naming scheme (eight alphanumeric characters with a three character extension) was replaced by "long" filenames, similar to the Microsoft DOS transition to VFAT in 1995. However, unlike VFAT, OS/A+ 4.1 disks were not backward compatible with earlier systems; Atari DOS or OS/A+ 2.1 could not read disks formatted by OS/A+ 4.1, breaking backward compatibility. The memory footprint was larger as well, resulting in insufficient memory to run some popular applications. As a result of these drawbacks, OS/A+ 4.1 did not achieve the market penetration as the earlier product. OSS did reissue OS/A+ 4.1 for a brief period when they decided not to modify DOS XL for double-sided disk support. DOS XL DOS XL was designed to replace OS/A+. Included support for single and double-density disk drives. Utilized the command-prompt of OS/A+ but also included a menu program. Featured extensions that took advantage of unused memory space in Atari XL/XE computers and OSS supercartridges. Included support for Indus GT Synchromesh. Due to lack of demand and Atari working on a new version of DOS, OSS decided to halt development of DOS XL 4 and reissue OS/A+ version 4.1. BASIC The team that developed Atari BASIC while at Shepherdson Microsystems developed a series of three increasingly sophisticated BASIC interpreters at OSS. BASIC A+ Atari BASIC was designed to fit in an 8K cartridge, with an optional cartridge for the second slot of the Atari 800 adding additional capability. The second cartridge was never produced. Instead, OSS produced the disk-based BASIC A Plus (or BASIC A+), which is compatible with Atari BASIC, corrects several bugs, and adds many new features. It includes PRINT USING (for formatted output), trace and debug enhancements, direct DOS commands, and explicit support for the graphics hardware including player/missile graphics. Because BASIC A+ had to be purchased, programs developed using its extended features could not be shared with people who did not own the interpreter. BASIC XL BASIC XL is a bank-selected cartridge version of the language that replaced BASIC A+. It fixes bugs and has even more features. The BASIC XL Toolkit contains additional code and examples for use with the BASIC XL and a runtime package for redistribution. A significant change in BASIC XL is the handling of line number lookups in GOTO/GOSUB and FOR...NEXT loops. In Atari BASIC, any GOTO searches the entire program for the provided line number, and FOR...NEXT loops use the same code. Microsoft BASIC simply jumps to a FOR statement via its address. The BASIC XL FAST command replaces constant targets of GOTO/GOSUB/NEXT with addresses. This gives a huge performance boost, making loops run as fast as Microsoft BASIC, and the program as a whole even faster. The downside is that an address becomes invalid if the program is edited during runtime, preventing it from being CONTinued, unlike Atari BASIC which generally allows this after any edit. Antic in 1984 stated that "BASIC XL is the fastest and most powerful version of BASIC available for Atari computers", with "exceptional" documentation. The magazine concluded that "This is the language that should be built into Atari computers. Is anyone at Atari listening?" BASIC XE BASIC XE is an enhanced version of the BASIC XL bank-selected cartridge, with additional functions and high-speed math routines. Because it requires 64KB, it only runs on an XL/XE systems. A runtime package was not released. The BASIC XL runtime can be used, but restricted to XL functions. Assemblers EASMD EASMD (Edit/ASseMble/Debug) is the first editor/assembler from OSS. Based on the original Atari Assembler Editor, it was released in 1981 on disk. It was superseded by MAC/65. MAC/65 MAC/65 is a 6502 editor and assembler originally released on disk in 1982, then on a bank-switched "supercartridge" in 1983 which includes an integrated debugger (DDT). Like Atari BASIC, MAC/65 uses line-numbered source code and tokenizes each line as it is entered. It is significantly faster than Atari's assemblers. The MAC/65 Toolkit disk contains additional code and examples. BUG/65 BUG/65 is a machine language debugger. It was initially included with MAC/65, but the cartridge-based version of the assembler added its own debugger, DDT. BUG/65 was later added to DOS XL. Other languages Action! A cartridge-based development system for a readable ALGOL-like language that compiles to efficient 6502 code. Action! combines a full-screen editor with a compiler that generates code directly to memory without involving disk access. The language found a niche for being over a hundred times faster than Atari BASIC, but much easier to program in than assembly language. Compiled Action! programs require the cartridge to be present, because standard library functions are on the cartridge. The separately available Action! Run-Time Package overcomes this limitation and allows distribution of Action!-compiled projects. The Action! Toolkit (originally called the Programmer's Aid Disk, or PAD) contains additional code and examples for use with the Action! language. C/65 C/65 is a compiler developed by LightSpeed Software for a subset of the C programming language. C/65 outputs assembly source code. An assembler like MAC/65 is needed to create an executable file. Tiny C Tiny C, stylized as tiny-c, is an interpreter for a subset of the C programming language; it was developed by Tiny C Associates. Personal Pascal A one-pass, machine code generating compiler for the Pascal language developed by J. Lohse for the Atari ST and released by OSS in 1987. It came with a 500+ page manual. Applications The Writer's Tool A word processing application available in a bank-selected cartridge and a double-sided disk (master disk on one side, dictionary disk on the other side). It was developed by Madison Micro and published by OSS in 1984. According to Bill Wilkinson, OSS was already building a word processor, but stopped when The Writer's Tool was submitted. SpeedRead+ SpeedRead+ is a speed reading tutor developed for the Atari 8-bit and Apple II computers. Sales According to Bill Wilkinson, OSS sold about 12,000 copies of Basic XL before the ICD merger. Basic XL outsold Action! by about 2.5 or 3 to 1. MAC/65 outsold Action! by about 1.5 to 1. Basic XE sold poorly, a money-loser. Personal Pascal sold over 10,000 copies. References Notes Wilkinson, Bill (1983). The Atari BASIC Source Book. Compute! Books. . A User's Guide and Reference Manual for DOS XL 2.30, 1983 OSS Newsletter - Spring 1984 OSS Newsletter - October 1984 External links Dan's tribute to OSS — A site dedicated to the products produced for Atari 8-bit computers by Optimized Systems Software. The Atari 400/800 and OSS Antic Vol. 4, No. 9 - Jan 1986 Basic XE from O.S.S. (Product Review) Defunct software companies of the United States Atari 8-bit family Software companies based in the San Francisco Bay Area Companies based in Cupertino, California American companies established in 1981 Software companies established in 1981 Software companies disestablished in 1988 1981 establishments in California 1988 disestablishments in California Defunct companies based in the San Francisco Bay Area

Operating System (OS)

OSF/1 OSF/1 is a variant of the Unix operating system developed by the Open Software Foundation during the late 1980s and early 1990s. OSF/1 is one of the first operating systems to have used the Mach kernel developed at Carnegie Mellon University, and is probably best known as the native Unix operating system for DEC Alpha architecture systems. In 1994, after AT&T had sold UNIX System V to Novell and the rival Unix International consortium had disbanded, the Open Software Foundation ceased funding of research and development of OSF/1. The Tru64 UNIX variant of OSF/1 was supported by HP until 2012. Background In 1988, during the so-called "Unix wars", Digital Equipment Corporation (DEC) joined with IBM, Hewlett-Packard, and others to form the Open Software Foundation (OSF) to develop a version of Unix named OSF/1. The aim was to compete with System V Release 4 from AT&T Corporation and Sun Microsystems, and it has been argued that a primary goal was for the operating system to be free of AT&T intellectual property. The fact that OSF/1 is one of the first operating systems to have used the Mach kernel is cited as support of this assertion. Digital also strongly promoted OSF/1 for real-time applications, and with traditional UNIX implementations at the time providing poor real-time support at best, the real-time and multi-threading support can be interpreted as having been heavily dependent on the Mach kernel. It also incorporates a large part of the BSD kernel (based on the 4.3-Reno release) to implement the UNIX API. At the time of its introduction, OSF/1 became the third major flavor of UNIX together with System V and BSD. Vendor releases DEC's first release of OSF/1 (OSF/1 Release 1.0) in January 1992 was for its line of MIPS-based DECstation workstations, however this was never a fully supported product. DEC ported OSF/1 to their new Alpha AXP platform as DEC OSF/1 AXP Release 1.2, released in March 1993. OSF/1 AXP is a full 64-bit operating system. After OSF/1 AXP V2.0 onwards, UNIX System V compatibility was also integrated into the system. OSF/1 v2 was also released for DECStation MIPS systems the same year. Subsequent releases are named Digital UNIX, and later, Tru64 UNIX. HP also released a port of OSF/1 to the early HP 9000/700 workstations based on the PA-RISC 1.1 architecture. This was withdrawn soon afterwards due to lack of software and hardware support compared to competing operating systems, specifically HP-UX. As part of the AIM alliance and the resulting PowerOpen specification, Apple Computer intended to base A/UX 4.0 for its PowerPC-based Macintoshes upon OSF/1, but the project was cancelled and PowerOpen deprecated. IBM used OSF/1 as the basis of the AIX/ESA operating system for System/370 and System/390 mainframes. OSF/1 was also ported by Kendall Square Research to its proprietary microarchitecture used in the KSR1 supercomputer. OSFMK The Open Software Foundation (akin to The Open Group) created OSFMK which is a commercial version of the Mach kernel for use in OSF/1. It contains applicable code from the University of Utah Mach 4 kernel (such as the "Shuttles" modification used to speed up message passing) and applicable code from the many Mach 3.0 variants that sprouted off from the original Carnegie Mellon University Mach 3.0 kernel. It also consists of improvements made by the OSF such as built-in collocation capability, realtime improvements, and rewriting of the IPC RPC component for better performance . OSF/1 AD OSF/1 AD (Advanced Development) was a distributed version of OSF/1 developed for massively parallel supercomputers by Locus Computing Corporation. Variants of OSF/1 AD are on several such systems, including the Intel Paragon XP/S and ASCI Red, Convex Exemplar SPP-1200 (as SPP-UX) and the Hitachi SR2201 (as HI-UX MPP). References Discontinued operating systems Mach (kernel) Microkernel-based operating systems Unix variants

Operating System (OS)

Acorn MOS The Machine Operating System (MOS) or OS is a discontinued computer operating system (OS) used in Acorn Computers' BBC computer range. It included support for four-channel sound, graphics, file system abstraction, and digital and analogue input/output (I/O) including a daisy-chained expansion bus. The system was single-tasking, monolithic and non-reentrant. Versions 0.10 to 1.20 were used on the BBC Micro, version 1.00 on the Electron, version 2 was used on the B+, and versions 3 to 5 were used in the BBC Master series. The final BBC computer, the BBC A3000, was 32-bit and ran RISC OS, which kept on portions of the Acorn MOS architecture and shared a number of characteristics (e.g. "star commands" CLI, "VDU" video control codes and screen modes) with the earlier 8-bit MOS. Versions 0 to 2 of the MOS were 16 KiB in size, written in 6502 machine code, and held in read-only memory (ROM) on the motherboard. The upper quarter of the 16-bit address space (0xC000 to 0xFFFF) is reserved for its ROM code and I/O space. Versions 3 to 5 were still restricted to a 16 KiB address space, but managed to hold more code and hence more complex routines, partly because of the alternative 65C102 central processing unit (CPU) with its denser instruction set plus the careful use of paging. User interface The original MOS versions, from 0 to 2, did not have a user interface per se: applications were expected to forward operating system command lines to the OS on its behalf, and the programming language BBC BASIC ROM, with 6502 assembler built in, supplied with the BBC Micro is the default application used for this purpose. The BBC Micro would halt with a Language? error if no ROM is present that advertises to the OS an ability to provide a user interface (called language ROMs). MOS version 3 onwards did feature a simple command-line interface, normally only seen when the CMOS memory did not contain a setting for the default language ROM. Application programs on ROM, and some cassette and disc-based software also, typically provide a command line, useful for working with file storage such as browsing the currently inserted disc. The OS provides the line entry facility and obeys the commands entered, but the application oversees running the command prompt. Cassette and disc based software typically relies on BBC BASIC's own user interface in order to be loaded, although it is possible to configure a floppy disk to boot up without needing to have BASIC commands executed, this was rarely used in practice. In BBC BASIC, OS commands are preceded with an asterisk or passed via the OSCLI keyword, to instruct BASIC to forward that command directly to the OS. This led to the asterisk being the prompt symbol for any software providing an OS command line; MOS version 3 onwards officially uses the asterisk as the command prompt symbol. When referring to an OS command, they generally include the asterisk as part of the name, for example , , etc., although only the part after the asterisk is the command. The asterisk was called a "star" and the commands were called "star commands". Unrecognised commands are offered to any service (extension) ROMs; filing system ROMs will often check to see if a file on disc matches that name, the same most other command-line interfaces do. The operating system call OSWORD with accumulator = 0 does however offer programs single line input (with ctrl-U for clear line and the cursor copying keys enabled) with basic character filtering and line length limit. The MOS command line interpreter features a rather unusual idea: abbreviation of commands. To save typing a dot could be used after the first few characters, such as for and for . was abbreviated to alone. , the command to catalogue (list) a cassette or disc, can be abbreviated down to . Service ROMs 3rd party ROMs generally also support command abbreviation, leading to ambiguity where two service ROMs provide commands which are very similar in name but possibly different in function. In this case, the MOS would prioritise the command from the ROM in the higher numbered ROM slot, e.g., 7 has precedence over 6. Some 3rd party suppliers would get around this by prefixing their star commands with other letters. For example, Watford Electronics ROMS would have their star commands prefixed with W thus making them unique. Extension The lower 16 KiB of the ROM map (0x8000 to 0xBFFF) is reserved for the active Sideways address space paged bank. The Sideways system on the BBC Micro allows for one ROM at a time from sockets on the motherboard (or expansion boards) to be switched into the main memory map. Software can be run from ROM this way (leaving the RAM free of user program code, for more workspace) and the OS can be extended by way of such ROMs. The most prevalent sideways ROM after BASIC is the Acorn Disc Filing System used to provide floppy disc support to the machine. During a reset, every paged ROM is switched in and asked how much public and private workspace it needs. Each ROM is allocated a chunk of private workspace that remains allocated at all times, and a single block of public workspace, equal to the size of the largest request, is made available to the active ROM. During operation, the paged area is rapidly switched between ROMs when file system commands are issued and unrecognised commands are put to the OS. MOS allocates a 3.5 KiB block of memory (0x0000 to 0x0DFF) from the bottom of the memory map for operating system and language ROM workspace: On a cassette-only machine, 0x0E00 is the start of user program memory. With OS extension ROMs fitted such as the a filing system ROM, more memory is allocated above this point; DFS ROMs generally use another 2.75 KiB to cache the disc catalogue and manage random access buffers. A network filing system ROM (for Econet) allocates another 0.5 KiB on top of this. This is a serious problem because MOS does not support relocation of machine code, which must be run from the address at which it was assembled, so some programs which assumed a fixed start of user program memory could overwrite MOS workspace. The problem was alleviated in versions 3 to 5 by allowing ROMs to allocate workspace in an alternative RAM bank at 0xC000 to 0xDFFF which was present in Master series computers, though old ROMs could continue to allocate blocks of main memory. The OS also maintains a vector table of all its calls which can be updated to hook any OS calls for user extension. By altering or 'hooking' these vectors, developers could substitute their own routines for those provided as defaults by the MOS. Text, graphics, printing The MOS permits textual output intended for the screen to be directed instead to the printer, or both at once, allowing for very trivial printing support for plain text. Graphics printing is not supported and has to be written separately. Graphics and in general all screen output is handled in a very unusual way. The ASCII control characters are almost entirely given new significance under MOS: known as the "VDU drivers", because the documentation described them in relation to the VDU statement in BBC BASIC, they are interpreted as video control characters. (i.e. ASCII 30) moves the cursor to (0, 0), VDU 4 and 5 select whether text should be drawn at the graphics or text cursor, VDU 12 clears the screen and VDU 14 and 15 turn scroll lock on and off. Thus, pressing ctrl-L will clear the screen and ctrl-N will enable scroll lock. VDU 2 and 3 toggle whether screen output is echoed to the printer. The BBC BASIC VDU statement is equivalent to the conventional BASIC and many of the control codes (such as 12 for "clear screen" and 7 for "beep") have the same functions as on other contemporary machines. Many more control characters take parameters: one or more characters that follow are used solely for their bit value as a parameter and not as a control code. VDU 19 handles palette remap; the following five bytes represent the palette entry, the desired colour and three reserve bytes. VDU 31 locates the text cursor to the location held in the following two bytes. VDU 17 sets the text colour and 18 the graphics colour. VDU 25 uses the succeeding five bytes to move the graphics cursor and plot solid and dashed lines, dots and filled triangles, the documented extent of graphics in MOS 0 and 1. The first byte is the command code, followed by the x and y co-ordinates as two byte pairs. Other graphic functions such as horizontal line fill bounded by a given colour were available by use of undocumented or poorly documented command codes. BBC BASIC contained aliases for the commonly used VDU codes (such as GCOL for VDU 18 or PLOT for VDU 25). Some statements were direct equivalents to VDU codes, such as CLS for VDU 12. Some statements were less exact equivalents as they incorporated functionality specific to BASIC as well as calling the OS routines; for example the statement would set screen mode and adjust the BASIC system variable HIMEM according to the amount of memory the new mode left available for BASIC, while would set the screen mode only, without altering HIMEM. This allowed a programmer to allocate a block of memory from BASIC for example to load machine code routines into by lowering the value of HIMEM at the start of a program, and still be free to switch screen modes without deallocating it as a side effect. There is one operating system command to write a character, OSWRCH, which is responsible for all text and graphics. For example, to move the cursor to (10, 15), needed, in 6502 assembler: LDA #31: JSR OSWRCH \ move text cursor LDA #10: JSR OSWRCH \ x-coordinate LDA #15: JSR OSWRCH \ y-coordinate (LDA loads a value into the accumulator; JSR is "jump to subroutine".) On the third OS call, the cursor will move. The following code would draw a line from (0, 0) to (0, +100): LDA #25: JSR OSWRCH \ begin "PLOT" (ASCII 25) command LDA #4: JSR OSWRCH \ command k=4, or move absolute LDA #0: JSR OSWRCH: JSR OSWRCH: JSR OSWRCH: JSR OSWRCH \ send (0, 0) as low, high byte pairs LDA #25: JSR OSWRCH \ begin PLOT LDA #1: JSR OSWRCH \ k=1 - draw relative LDA #0: JSR OSWRCH: JSR OSWRCH \ x = 0 LDA #100: JSR OSWRCH \ y = 100 (low byte) LDA #0: JSR OSWRCH \ high byte BBC BASIC allows performing the above as any of the following: VDU 25, 4, 0; 0; 25, 4, 100; 0; PRINT CHR$(25); CHR$(4); CHR$(0); ... etc. PLOT 4, 0, 0: PLOT 1, 0, 100 MOVE 0, 0: DRAW 0, 100: REM absolute co-ords only! OSWRCH=&FFEE: A%=25: CALL OSWRCH: A%=4: CALL OSWRCH: A%=0: CALL OSWRCH ... etc. Graphics in the Acorn MOS use a virtual graphics resolution of 1280×1024, with pixel positions mapped to the nearest equivalent pixel in the current graphics mode. Switching video resolution will not affect the shape, size or position of graphics drawn even with completely different pixel metrics in the new mode, because this is all accounted for by the OS. MOS does provide two other OS calls that handle text output: OSNEWL and OSASCI. OSNEWL writes a line feed and carriage return to the current output stream. OSASCI forwards all characters directly to OSWRCH except for carriage return, which triggers a call to OSNEWL instead. The precise code for OSASCI and OSNEWL five lines of 6502 assembler is documented in the BBC Micro User Guide. MOS implements character recognition so that text printed on screen in the system font can be selected with the arrow keys and input with the key as though it was being typed. To activate screen editing the user moves the hardware cursor to the text to be read and the OS displays a second cursor in software at the original position. Pressing copies one character from the hardware cursor to the software cursor and advances both, so that holding the key down copies a section of the text, the cursors wrapping around the vertical edges of the screen as necessary. If the screen scrolls during editing, the hardware cursor's position is adjusted to follow the text. The user can make changes to the text during the copy, and user-defined characters are recognised in graphics modes. Screen editing is terminated when or are pressed, which have their usual effects. Character recognition is made available to users in the API with a call to read the character at the current cursor position. Sound Sound generation is carried out through another OS call, OSWORD, which handles a variety of tasks enumerated via a task code placed into the accumulator. All OSWORD calls bear a parameter block used to send and receive multiple data; the address of this block is passed in the X and Y registers, with the low byte in X and the high byte in Y. There are four buffered sound channels three melodic and one noise-based on the sound chip found in the BBC Micro. There is only one waveform for melodic channels; the supported note parameters are pitch, duration, amplitude, envelope selection and various control options. For the amplitude parameter, a zero or negative sets a static amplitude, and a positive value select an amplitude and pitch envelope (a predefined temporal variation) to apply to the note. Control parameters was passed through the channel parameter, and include flush (the buffer is cleared and the channel silenced before the note is played), synchronise count (as soon as the same sync count is received for that many channels, all the synchronised notes are played together), and control over the Speech system upgrade where fitted. OSWORD handles many functions other than sound, many of which do not have direct support in BASIC. They may be accessed from BASIC by setting up the parameter block, loading its address into X% and Y% and the task code into A%, and then calling the routine. Other I/O and second processor support The BBC Micro had support for a second processor connected via the Tube, which allowed direct access to the system bus. The driver code for the Tube interface is not held in the MOS, usually being supplied by an external service ROM. The OS has calls to handle reading and writing to all I/O (ports and screen memory) and programmers are strongly advised to use these by the Acorn documentation. The reason for this is that when a second processor is installed, user software is run from the separate memory map on the far side of the Tube processor bus, and direct access to memory-mapped I/O registers and video memory is impossible. However, for the sake of performance, many apps including many games, write directly to main address space for I/O, and hence crash or give a blank screen if a 6502 second processor is attached. One such performance-critical area is sprite support: BBC Micro hardware does not support sprites, and games must implement sprites in software. In practice, the widespread use of direct access in place of the OS calls very rarely caused problems. Second processor units were expensive and very little software was written to make use of them, so few people bought them, and those who did have them could simply switch them off or unplug the cable if a problem arose. The MOS contains two built-in file systems: cassette and ROM. These are quite similar (try , , with a suitable ROM installed) and share a great deal of code. They feature a rudimentary copy protection mechanism where a file with a certain flag set cannot be loaded except to execute it. (Before Amstrad's launch of a mass-market twin cassette recorder in 1987, most home users did not have facilities to dub cassettes without loading the files into the computer for re-saving.) The Advanced Disc Filing System (ADFS), installed as standard in the Master series, has a similar mechanism. Versions Releases 0 and 1 Versions for the BBC Micro family, starting at 0.10 and finishing at 1.20. Confusingly the Electron shipped with version 1.00 despite being released after the BBC Micro's version 1.20, because it was the first release of a ROM for the electron. The MOS version number was not intended as an API definition: the Electron ROM was not "based on" the BBC Micro ROM version 1.0 in any sense. Release 2 This version is for the BBC Model B+, essentially the same as MOS 1.20 except with the addition of support for the sideways and shadow RAM present on the B+. Releases 3 to 5 MOS 3 to MOS 5 shipped with the BBC Master Series systems, in the Master 128, Master ET, and Master Compact models respectively. The initial release of MOS 3 expanded upon the facilities provided in MOS 2 on the B+ to support additional hardware, provide a command line facility and extend the VDU driver code with enhanced graphics plotting abilities. Two notable versions were made public: version 3.20 being the most common, and version 3.50 (although this had more functionality and bug fixes it was not 100% compatible with some popular applications software so was offered as an optional upgrade only). MOS 4 was a stripped down version of MOS 3 intended for the similarly minimized Master ET, and a few minor bugs fixed. MOS 5 shipped with the Master Compact, and was much altered with some functions removed or highly amended. Credits With the exception of MOS 3.50 where the space was reclaimed for more code, the area normally hidden by the input/output memory locations (the 768 bytes from 0xFC00-0xFEFF inclusive) in the MOS ROM contained a list of names of contributors to the system. This could be recovered by extracting the ROM and reading its contents in an EPROM programmer. Those who did not have such a device could access the ROM on a Master by setting a test bit of an access control register, then using a machine-code program to copy the ROM directly to text-mode screen memory. The full text of the credit string in MOS 1.20 is as follows; no spaces occur after the commas to save memory: "(C) 1981 Acorn Computers Ltd.Thanks are due to the following contributors to the development of the BBC Computer (among others too numerous to mention):- David Allen,Bob Austin,Ram Banerjee,Paul Bond,Allen Boothroyd,Cambridge,Cleartone,John Coll,John Cox,Andy Cripps,Chris Curry,6502 designers,Jeremy Dion,Tim Dobson,Joe Dunn,Paul Farrell,Ferranti,Steve Furber,Jon Gibbons,Andrew Gordon,Lawrence Hardwick,Dylan Harris,Hermann Hauser,Hitachi,Andy Hopper,ICL,Martin Jackson,Brian Jones,Chris Jordan,David King,David Kitson,Paul Kriwaczek,Computer Laboratory,Peter Miller,Arthur Norman,Glyn Phillips,Mike Prees,John Radcliffe,Wilberforce Road,Peter Robinson,Richard Russell,Kim Spence-Jones,Graham Tebby,Jon Thackray,Chris Turner,Adrian Warner,Roger Wilson,Alan Wright." Reception In interviews in 1993 and 2001, Acorn cofounder Hermann Hauser recounted that Microsoft's Bill Gates, having noticed that 1.5 million BBC Micros were sold, tried to sell MS-DOS to Acorn, but Hauser considered that adopting MS-DOS would have been a "retrograde step" compared to retaining Acorn's system. References Notes Watford Electronics, "The Advanced Reference Manual for the BBC Master Series", 1988 Acorn operating systems Discontinued operating systems 1981 software

Operating System (OS)

Internet OS An Internet operating system, or Internet OS, is any type of operating system designed to run all of its applications and services through an Internet client, generally a web browser. The advantages of such an OS would be that it would run on a thin client, allowing cheaper, more easily manageable computer systems; it would require all applications to be designed on cross-platform, open standards; and would not tie a user's applications, documents, and preferences to a single computer, but rather place them in the Internet cloud. The Internet OS has also been promoted as the perfect type of platform for software as a service. History Talk of an Internet OS began to surface in 1995 as the browser war started heating up between Microsoft and Netscape. In response to the limited capabilities of HTML at the time, Microsoft began developing an online content authoring platform that would be based on distributed OLE (Object Linking and Embedding) which it codenamed Blackbird. Using OLE, applications put on the web would contain their own processing logic, so would act similar to applications in a typical desktop environment. Immediately, there were concerns that this would tie the web to proprietary Microsoft technology that wouldn't be guaranteed to run across different systems. As a challenge, Marc Andreessen of Netscape announced a set of new products that would help transform their browser into what he called an "Internet OS" that would provide the tools and programming interfaces for a new generation of Internet-based applications. The so-called "Internet OS" would still run on top of a regular OS – being based around Netscape Navigator – but he dismissed desktop operating systems like Windows as simply "bag[s] of drivers", reiterating that the goal would be to "turn Windows into a mundane collection of not entirely debugged device drivers". Andreessen explained that the newest versions of Navigator were not just web browsers, but suites of Internet applications, including programs for mail, FTP, news, and more, and would come with viewers for a variety of document types, like Adobe Acrobat, Apple QuickTime, and Sun Java applets, which would give it programming interfaces and publishing tools for developers. Netscape also would continue to sell its server software, and Java applets would run cross-platform on both its clients and its servers, and as a scripting language in the form of JavaScript. They would also provide facilities for backend transaction processing, elaborating the client/server model with navigating clients and application servers and database servers. He pointed out – because of the broad capabilities that all of this gave their browser – the only difference technically between Netscape Navigator and a traditional operating system is that Navigator didn't include device drivers. Technical problems with Blackbird, the growth of the web, and what they saw as competitive statements from Netscape, soon led Microsoft to rethink their strategy and they began to position OLE as a primary tool within Netscape's proposed ecosystem. OLE would now be embeddable in web pages using an ActiveX plug-in, and would be easily integrated on the server side using ASP (Active Server Pages) development. The "Gang of Five" and the NC Opposition in the industry to Microsoft began to grow, as did the concept of an "Internet OS", and this led to the formation of an alliance around developing Java as an alternative to Windows – the chief partners being Netscape, Sun, Oracle, and IBM. These companies were informally referred to in the industry press as the "Gang of Four". Novell later joined the alliance, leading it to be called the "Gang of Five". In May 1997, the group published a position paper which discussed integration of software component models within CORBA – a commonly used architecture allowing computer applications from different vendors running on different systems to work together over networks. From this, they then issued several RFPs (Request for Proposals) to the Object Management Group (OMG), the standards body responsible for managing CORBA, meant to help integrate different aspects of Java. The proposals included support for JavaBeans – the serialized, component architecture of Java – and for JavaScript. In what was called the "Java-tization of CORBA", the group was positioning Java to be a distributed object architecture, similar to what Microsoft had intended with OLE in Blackbird. OLE would only exist as a second-class technology that would interface through CORBA using JavaBeans. The group also promoted the idea of a JavaOS – a minimal, Java-based operating system – which would in turn run Netscape's web browser, and through the browser run JavaBeans components. This would be the front for a new ecosystem based on open standards; first, HTML in the web browser; and second, Java, which they hoped would become widely adopted through CORBA. JavaOS would be hosted on a Network Computer (or NC), a concept long advocated by Oracle. The NC would be a thin client designed only for Internet use, leaving it to access applications and documents stored entirely online. Oracle saw its role as providing tools for the server layer, where network-hosted applications would be provided through the Network Application Server, which in turn would make use of both Oracle7 relationship database management system and the Oracle Web Server. Oracle also outlined what was referred to as the Network Computing Architecture (NCA), which would separate presentation, application and data access logic into Java applets or NCA cartridges. Microsoft and Intel in response to this challenge put forward a standard for a competing model called the NetPC, a diskless PC that would be primarily adapted to web browser use and would run a simplified version of Windows 95, codenamed Pegasus. Later down the road, this idea evolved into the Netbook. Microsoft publicly criticized the idea of an Internet OS, and instead argued that the traditional desktop OS should be Internet-enabled, the beginning of the idea for Active Platform, an Internet strategy that culminated later in the release of Windows 98. This strategy, which involved tightly bundling Internet Explorer in Windows, became the center of a United States anti-trust suit against Microsoft. All of the Gang of Five – Netscape, Sun, IBM, Oracle, and Novell – were involved in lobbying for anti-trust action against Microsoft. By 1998, the Java alliance started to fall apart. Oracle continued developing server-side Java databases but had given up the idea of the network computer and Netscape had given up on their Java browser efforts, instead aiming to position themselves as an Internet portal. Pressure from investors was given the blame. Chrome OS and Chromium OS Google revived the idea of the Internet OS in 2009 with the development of Chrome OS, a Linux-based operating system designed to work exclusively with AJAX-based web applications. The operating system was designed to look and operate like the Chrome web browser and be sold on laptops developed with partners, called Chromebooks. They also promoted G Suite, their suite of web applications, as an alternative to traditional desktop software such as Microsoft Office. Google has tried to address standard criticisms of the Internet OS concept with its development projects. Google Native Client allows a browser to run Intel x86 native code in a sandbox, so that more complex programs could run that more fully take advantage of a system's hardware. Google Gears was also created to allow offline access of online applications, although this is being deprecated in favour of web storage, a model in the process of standardization by the World Wide Web Consortium (W3C). Chromium OS is the development version of Chrome OS, but until Chrome OS, Chromium OS principal user interface is the Chromium web browser rather, which is fully free and open-source, rather than the commercial Google Chrome web browser version. As such Chromium OS does therefor not ship any of Google's branding and proprietary cloud services preinstalled. See also Kiosk software Cloud computing DR-WebSpyder References Cloud clients Web desktops

Operating System (OS)

OS-9 OS-9 is a family of real-time, process-based, multitasking, multi-user operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It was purchased by Radisys Corp in 2001, and was purchased again in 2013 by its current owner Microware LP. The OS-9 family was popular for general-purpose computing and remains in use in commercial embedded systems and amongst hobbyists. Today, OS-9 is a product name used by both a Motorola 68000-series machine language OS and a portable (PowerPC, x86, ARM, MIPS, SH4, etc.) version written in C, originally known as OS-9000. History The first version ("OS-9 Level One"), which dates back to 1979–1980, was written in assembly language for the Motorola 6809 CPU, and all of its processes ran within the 64KB address space of the CPU without a memory management unit. It was developed as a supporting operating system for the BASIC09 project, contracted for by Motorola as part of the 6809 development. A later 6809 version ("Level Two") takes advantage of memory mapping hardware, supported up to 2 MB of memory (ca. 1980) in most implementations, and included a GUI on some platforms. In 1983, OS-9/6809 was ported to Motorola 68000 assembly language and extended (called OS-9/68K); and a still later (1989) version was rewritten mostly in C for further portability. The portable version was initially called OS-9000 and was released for 80386 PC systems around 1989, then ported to PowerPC around 1995. These later versions lack the memory mapping facilities of OS-9/6809 Level Two simply because they do not need them. They used a single flat address space that all processes share; memory mapping hardware, if present, is mostly used to ensure that processes access only memory they have the right to access. The 680x0 and 80386 (and later) MPUs all directly support far more than of memory in any case. As a consequence of early pervasive design decisions taking advantage of the easily used reentrant object code capabilities of the 6809 processor, programs intended for OS-9 are required to be reentrant; compilers produce reentrant code automatically and assemblers for OS-9 offer considerable support for it. OS-9 also uses position-independent code and data because the 6809 also supports it directly; compilers and assemblers support position independence. The OS-9 kernel loads programs (including shared code), and allocates data, wherever sufficient free space is available in the memory map. This allows the entire OS and all applications to be placed in ROM or Flash memory, and eases memory management requirements when programs are loaded into RAM and run. Programs, device drivers, and I/O managers under OS-9 are all 'modules' and can be dynamically loaded and unloaded (subject to link counts) as needed. OS-9/6809 runs on Motorola EXORbus systems using the Motorola 6809, SS-50 Bus and SS-50C bus systems from companies such as SWTPC, Tano, Gimix, Midwest Scientific, and Smoke Signal Broadcasting, STD-bus 6809 systems from several suppliers, personal computers such as the Fujitsu FM-11, FM-8, FM-7 and FM-77, Hitachi MB-S1, and many others. System Industries, a third-party provider of DEC compatible equipment, used a 68B09E processor running OS9 in its QIC (quarter-inch cartridge) tape backup controllers in VAX installations. The best known hardware (due to its low price and broad distribution) was the TRS-80 Color Computer (CoCo) and the similar Dragon series. Even on the CoCo, a quite minimalist hardware platform, it was possible under OS-9/6809 Level One to have more than one interactive user running concurrently (for example, one on the console keyboard, another in the background, and perhaps a third interactively via a serial connection) as well as several other non-interactive processes. A second processor implementation for the BBC Micro was produced by Cumana. It included on-board RAM, SCSI hard disk interface and a MC68008 processor. OS-9 was also ported to the Commodore SP-9000 or SuperPET, which had a 6809 in addition to the 6502 of the base 8032 model, as well as 64 KB more. The Toronto PET Users Group sponsored a HW/SW project which included a daughter board with an MMU as well as the OS-9 distribution disks. With two processors, 96 KB, a 25×80 screen and serial, parallel and IEEE-488 ports and many peripherals this was one of the most capable OS-9 systems available. OS-9's multi-user and multi-tasking capabilities make it usable as a general-purpose interactive computer system. Many third-party interactive applications have been written for it, such as the Dynacalc spreadsheet, the VED text formatter, and the Stylograph and Screditor-3 WYSIWYG word processors. TSC's nroff emulating formatter was ported to OS-9 by MicroWay, as well. In mid 1980s, OS-9 was selected for the CD-i operating system. Around the same time, Microsoft approached Microware for acquisition of the company primarily because it was attracted by CD-RTOS, the CD-i operating system. The negotiation failed and no deal was made; Microware decided to remain independent. In late 1980s, Microware released OS-9000, a more portable version of the operating system. The vast majority of the operating system kernel was rewritten in C leaving a handful of hardware-dependent parts in assembly language. A few "more advanced features" were added such as tree-like kernel module name space. OS-9000 was initially ported to the Motorola 680x0 family CPUs, Intel 80386, and PowerPC. The OS-9000/680x0 was a marketing failure and withdrawn very quickly, probably because few customers wanted to try the fatter and slower operating system over the existing OS-9/680x0 proven record of stability. That the Motorola 680x0 family and VME board computer system vendors were nearing their end of life might have affected the unpopularity of OS-9000/680x0. Microware later started calling all of its operating systems — including what had been originally called OS-9000 — simply OS-9, and started shifting its business interest towards portable consumer device markets such as cellphones, car navigation, and multimedia. In late 1980s and early 1990s, the Character Generators computers used in Broadcast Systems used OS-9 and OS-9000 extensively. The now defunct Pesa Electronica used OS-9 on their CGs such as CG 4722 and CG4733. Name conflicts and court decisions In 1999, nineteen years after the first release of OS-9, Apple Computer released Mac OS 9. Microware sued Apple that year for trademark infringement, although a judge ruled that there would be little chance for confusion between the two. Some Macintosh users who are unaware of Microware's lesser known OS-9 have posted to the comp.os.os9 newsgroup not realizing what OS-9 is. In 2001, RadiSys purchased Microware to acquire the Intel IXP-1200 network processor resources. This acquisition infused Microware with capital and allowed Microware to continue OS-9 development and support. On 21 February 2013, Microware LP (a partnership formed by Freestation of Japan, Microsys Electronics of Germany and RTSI LLC of the USA) announced that they signed an Asset Purchase Agreement to buy the rights to the names Microware, OS-9 and all assets from RadiSys. Technology Modern and archaic design OS-9 (especially the 68k version and thereafter) clearly distinguishes itself from the prior generation of embedded operating systems in many aspects. Runs on 8-bit, 16-bit, and 32-bit CPUs. Clear separation between user mode and supervisor (kernel) mode. Dynamic use of individually and separately built software components (executable program images and kernel modules) rather than a statically linked single monolithic image. Unix-like process name-space model (not memory model) and user shell program. Clear separation between hardware independent (e.g. file managers) and hardware dependent (e.g. device drivers) layers. When compared with more modern operating systems: The kernel is written entirely in assembly language (OS-9/68K version only) and C (portable version to other architectures) using simple internal data structures, reducing flexibility and improvement scope while improving determinability required for real-time operating systems. Performance was also affected for some operations, but assembly language helped with the speed issue. Systems without a memory management unit (MMU) have no memory protection against illegal access, nor per-process memory protection, while systems with an MMU can have memory protection enabled. The module controlling the MMU can be included or omitted by the system integrator to enable or disable memory protection. This allows OS-9 to run on older systems which do not include an MMU. Older versions of OS-9 do not support POSIX threads, while all OS-9 supported processors support POSIX threads. No SMP support for multiple sockets, cores, or hardware threads in the same OS-9 instance (can run as a RTOS on one of the cores of dual core processors like Core Duo and Core 2 Duo, when Linux is running on the other core doing general purpose tasks). Task scheduling OS-9's real-time kernel allows multiple independent applications to execute simultaneously through task switching and inter-process communication facilities. All OS-9 programs run as processes containing at least one lightweight process (thread) but may contain an effectively unlimited number of threads. Within a process, these lightweight processes share memory, I/O paths, and other resources in accordance with the POSIX threads specification and API. OS-9 schedules the threads using a fixed-priority preemptive scheduling algorithm with round-robin scheduling within each priority. Time slicing is supported. The priority levels can be divided into a range that supports aging and a higher-priority range that uses strict priority scheduling. Each process can access any system resource by issuing the appropriate OS-9 service request. At every scheduling point, OS-9 compares the priority of the thread at the head of the active queue to the priority of the current thread. It context switches to the thread on the active queue if its priority is higher than the current processes' priority. Aging artificially increases the effective priority of threads in the active queue as time passes. At defined intervals, time slicing returns the current thread to the active queue behind other threads at the same priority. Kernel modules Kernel – Contains task switching, memory allocation, and most non-I/O calls IOMAN – Handles I/O calls to various file managers and drivers. File managers basic set: SCF, Serial files (serial devices) RBF, Random block (disk devices) SBF, Sequential block (tape Devices) NFM, NULL devices (USB and other devices) MFM, Message PCF, PC FAT files PIPEMAN, Pipe manager Modman - Memory module directories SSM – System security (MMU handling) Cache – Cache handling, VectXXX – Vector / PIC handler FPU – Floating point emulation Align – Address alignment fault handler Commands The following list of commands is supported by the OS-9 shell. Shell built-in commands chd chx kill w wait setenv unsetenv setpr logout profile ex -e -ne -p -p=<str> -np -t -nt -v -nv -x -nx Utilities for operating system functions attr copy date deiniz del deldir dsave dump echo fixmod free ident iniz link list load makdir mdir merge mfree pd pr printenv procs rename save shell setime sleep tee tmode touch unlink System management utilities backup dcheck devs format frestore fsave irqs login os9gen tsmon xmode General utilities binex build cfp cmp code compress count edt exbin expand grep help make qsort tr umacs Comparisons with Unix OS-9's notion of processes and I/O paths is quite similar to that of Unix in nearly all respects, but there are some significant differences. Firstly, the file system is not a single tree, but instead is a forest with each tree corresponding to a device. Second, OS-9 does not have a Unix-style fork() system call—instead it has a system call which creates a process running a specified program, performing much the same function as a fork-exec or a spawn. Additionally, OS-9 processes keep track of two "current directories" rather than just one; the "current execution directory" is where it will by default look first to load programs to run (which is similar to the use of PATH environment variable under UNIX). The other is the current data directory. Another difference is that in OS-9, grandparent directories can be indicated by repeating periods three or more times, without any intervening slashes (a feature also found in 4DOS/4OS2/4NT/TC). For example, ..../file in OS-9, is similar to ../../../file in Unix. But . and .., with just one or two periods, each work the same in both OS-9 and Unix. OS-9 has had a modular design from the beginning, influenced by notions of the designers of the 6809 and how they expected software would be distributed in the future (see the three-part series of articles in January-March 1979 Byte by Terry Ritter, et al. of Motorola who designed the CPU). The module structure requires more explanation: OS-9 keeps a "module directory", a memory-resident list of all modules that are in memory either by having been loaded, or by having been found in ROM during an initial scan at boot time. When one types a command to the OS-9 shell, it will look first in the current module directory for a module of the specified name and will use it (and increase its link count) if found, or it will look on disk for an appropriately named file if not. In OS-9/6809 and OS-9/68000, the module directory is flat, but OS-9000 made the module directory tree-structured. The OS-9000 shell looks in one's alternative module directory for a MODPATH environment variable, analogous to the PATH variable in all versions, indicating the sequence of module directories in which to look for pre-loaded modules. Modules are not only used to hold programs, but can also be created on the fly to hold data, and are the way in which OS-9 supports shared memory. OS-9/non-68000 supports POSIX threads. A single process can start any number of threads. Status OS-9 has faded from popular use, though Microware LP does still support it and it does run on modern architectures such as ARM and x86. The compiler provided, Ultra C/C++, supports C89, but supports neither C99 nor C++98. Ultra C++ does provide limited support for C++ templates. It is also supported by popular SSL/TLS libraries such as wolfSSL. A Version of OS-9 running Steve Adams' G-Windows is present on semiconductor wafer scrubbers manufactured by Ontrak Systems / Lam Research. Thousands of these systems are in use today, however, the software running on them dates to 1999 when the last version was created to handle Y2K issues. Versions of OS-9/68K ran on a wide variety of 68000 family platforms, including the Sharp X68000 in Japan, some personal computers intended by their designers as upgrades from the Color Computer (e.g., the 68070 and 68340-based MM/1, and on other computers from Frank Hogg Laboratories, PEP Modular Computers, and Delmar Co.) It was also ported to the Atari ST by Recc-o-ware in the early 1990s, and was distributed by Cumana in Europe. A port for 68000-based Apple Macintoshes distributed by Ultrascience exists. A port to the Amiga by Digby Tarvin is also purported to exist. OS-9/68K is mandated by Caltrans to be used in the 2070-1B and 2070-1E controller cards, and so ends up being used to run many North American traffic signal control systems. OS-9/68K is also found in some other embedded applications, including the Quanta Delta television broadcast character generator, still in production by ScanLine Technologies in Utah. While the user-level interface code on this system started at boot time, there was a hidden, undocumented keyboard sequence that would provide a user with a root shell prompt in a scroll window on the device's edit-channel monitor. In the embedded market, where OS-9 has found application in such devices as the Fairlight CMI synthesizers, robotics, in-car navigation systems, and Philips' Compact Disc-Interactive (CD-i) industry standard. The TRS-80 Color Computer (and clones) still has users and an annual conference in Chicago; as of 2018 the 27th Annual "Last" Chicago CoCoFEST was scheduled for 21-22 April 2018. A group of Canadian programmers rewrote OS-9/6809 Level II for the CoCo 3 (w/ address translation hardware) for efficiency, and to take advantage of the native mode of the Hitachi 6309. Today's serious CoCo users now typically have replaced the 68B09E in the CoCo 3 with an Hitachi 63B09E and run the rewrite, called NitrOS-9. The combination is surprisingly fast, considering that it runs on an expressly low cost, 8-bit computer system. Gary Becker's CoCo3 FPGA is a synthesized TRS-80 Color Computer which runs NitrOS-9 on an Altera DE-1 development board. The core 6809 CPU was designed by John Kent and is currently running at 25 MHz. OS-9000/80x86 can be run on PC-type machines built around the Intel x86 CPUs. OS-9000 has also been ported to the PowerPC, MIPS, some versions of Advanced RISC Machines' ARM processor, and some of the Hitachi SH family of processors. The DigiCart/II Plus audio playback unit runs OS-9/68K. It is a solid state replacement for radio station style cart players. These units are used in radio and at places like Walt Disney World where they play park announcements. German electronics manufacturer Eltec has been manufacturing the Eurocom-model CPU boards for industrial purposes since the late 1970s, starting with the 6802 and 6809 Eurocom-1 and Eurocom-2, and onwards with 68K, and derivative, CPU boards up to today. The modern boards can be delivered with a range of operating systems, amongst which is OS-9. Omron used OS-9 in their NS series HMI panels. However, for their new NA series, Omron selected Windows Embedded Compact 7. Omron indicated that with OS-9 nearly all the drivers, for example for a USB stick, had to be written by Omron. References Further reading External links Microware LP DTR - Access OS-9 Disk on PC OS-9 Frequently Asked Questions List Archive of OS-9 information and software, from RTSI LLC. Repository for command line tools for manipulating 6809 OS-9 disk images, on SourceForge Execution environment for OS-9 user-mode programs on Mac/Win/linux host OS NitrOS-9 official website, on SourceForge An OS-9 Port to the Thomson MO5, emulation (fr) Running OS-9 on a TRS-80 Color Computer (CoCo) comp.os.os9 newsgroup via Google groups web interface. Official OS-9 Blog A 6809 Emulator based on the SWTPC 6809 system that runs OS9 and UniFLEX as well as FLEX XiBase9 (a GUI) DragonWiki Real-time operating systems Embedded operating systems TRS-80 Color Computer ARM operating systems X86 operating systems PowerPC operating systems Proprietary operating systems

Operating System (OS)

THE multiprogramming system The THE multiprogramming system or THE OS was a computer operating system designed by a team led by Edsger W. Dijkstra, described in monographs in 1965-66 and published in 1968. Dijkstra never named the system; "THE" is simply the abbreviation of "Technische Hogeschool Eindhoven", then the name (in Dutch) of the Eindhoven University of Technology of the Netherlands. The THE system was primarily a batch system that supported multitasking; it was not designed as a multi-user operating system. It was much like the SDS 940, but "the set of processes in the THE system was static". The THE system apparently introduced the first forms of software-based paged virtual memory (the Electrologica X8 did not support hardware-based memory management), freeing programs from being forced to use physical locations on the drum memory. It did this by using a modified ALGOL compiler (the only programming language supported by Dijkstra's system) to "automatically generate calls to system routines, which made sure the requested information was in memory, swapping if necessary". Paged virtual memory was also used for buffering input/output (I/O) device data, and for a significant portion of the operating system code, and nearly all the ALGOL 60 compiler. In this system, semaphores were used as a programming construct for the first time. Design The design of the THE multiprogramming system is significant for its use of a layered structure, in which "higher" layers depend on "lower" layers only: Layer 0 was responsible for the multiprogramming aspects of the operating system. It decided which process was allocated to the central processing unit (CPU), and accounted for processes that were blocked on semaphores. It dealt with interrupts and performed the context switches when a process change was needed. This is the lowest level. In modern terms, this was the scheduler. Layer 1 was concerned with allocating memory to processes. In modern terms, this was the pager. Layer 2 dealt with communication between the operating system and the system console. Layer 3 managed all I/O between the devices attached to the computer. This included buffering information from the various devices. Layer 4 consisted of user programs. There were 5 processes: in total, they handled the compiling, executing, and printing of user programs. When finished, they passed control back to the schedule queue, which was priority-based, favoring recently started processes and ones that blocked because of I/O. Layer 5 was the user; as Dijkstra notes, "not implemented by us". The constraint that higher layers can only depend on lower layers was imposed by the designers in order to make reasoning about the system (using quasi-formal methods) more tractable, and also to facilitate building and testing the system incrementally. The layers were implemented in order, layer 0 first, with thorough testing of the abstractions provided by each layer in turn. This division of the kernel into layers was similar in some ways to Multics' later ring-segmentation model. Several subsequent operating systems have used layering to some extent, including Windows NT and macOS, although usually with fewer layers. The code of the system was written in assembly language for the Dutch Electrologica X8 computer. This computer had a word size of 27 bits, 32 kilowords of core memory, 512 kilowords of drum memory providing backing store for the LRU cache algorithm, paper tape readers, paper tape punches, plotters, and printers. See also RC 4000 Multiprogramming System Ring (computer security) Timeline of operating systems References Assembly language software Discontinued operating systems Dutch inventions Computer science in the Netherlands Information technology in the Netherlands Edsger W. Dijkstra 1968 software

Operating System (OS)

Object-oriented operating system An object-oriented operating system is an operating system that is designed, structured, and operated using object-oriented programming principles. An object-oriented operating system is in contrast to an object-oriented user interface or programming framework, which can be run on a non-object-oriented operating system like DOS or Unix. There are already object-based language concepts involved in the design of a more typical operating system such as Unix. While a more traditional language like C does not support object-orientation as fluidly as more recent languages, the notion of, for example, a file, stream, or device driver (in Unix, each represented as a file descriptor) can be considered a good example of objects. They are, after all, abstract data types, with various methods in the form of system calls which behavior varies based on the type of object and which implementation details are hidden from the caller. Object-orientation has been defined as objects + inheritance, and inheritance is only one approach to the more general problem of delegation that occurs in every operating system. Object-orientation has been more widely used in the user interfaces of operating systems than in their kernels. Background An object is an instance of a class, which provides a certain set of functionalities. Two objects can be differentiated based on the functionalities (or methods) they support. In an operating system context, objects are associated with a resource. Historically, the object-oriented design principles were used in operating systems to provide several protection mechanisms. Protection mechanisms in an operating system help in providing a clear separation between different user programs. It also protects the operating system from any malicious user program behavior. For example, consider the case of user profiles in an operating system. The user should not have access to resources of another user. The object model deals with these protection issues with each resource acting as an object. Every object can perform only a set of operations. In the context of user profiles, the set of operations is limited by privilege level of a user. Present-day operating systems use object-oriented design principles for many components of the system, which includes protection. Examples Athene Athene is an object-based operating system first released in 2000 by Rocklyte Systems. The user environment was constructed entirely from objects that are linked together at runtime. Applications for Athene could also be created using this methodology and were commonly scripted using the object scripting language Dynamic Markup Language (DML). Objects could have been shared between processes by creating them in shared memory and locking them as needed for access. Athene's object framework was multi-platform, allowing it to be used in Windows and Linux environments for developing object-oriented programs. The company went defunct and the project abandoned sometime in 2009. BeOS One attempt at creating a truly object-oriented operating system was the BeOS of the mid 1990s, which used objects and the C++ language for the application programming interface (API). But the kernel was written in C with C++ wrappers in user space. The system did not become mainstream and proved commercially unviable. Now it is being used and developed by a small group of enthusiasts. Choices Choices is an object-oriented operating system developed at the University of Illinois at Urbana–Champaign. It is written in C++ and uses objects to represent core kernel components like the central processing unit (CPU), processes, and so on. Inheritance is used to separate the kernel into portable machine-independent classes and small non-portable dependent classes. Choices has been ported to and runs on SPARC, x86, and ARM. GEOS PC/GEOS is a light-weight object-oriented multitasking graphical operating system with sophisticated window and desktop management featuring scalable fonts. It is mostly written in an object-oriented x86 assembly language dialect and some C/C++ and is designed to run on DOS (similar to Microsoft Windows up to Windows Me). GEOS was developed originally by Berkeley Softworks in 1990, which later became GeoWorks Corporation, and it is continued to be maintained by BreadBox Computer Company. Related software suites were named Ensemble and New Deal Office. Adaptations exist for various palmtops, and 32-bit systems with non-x86-CPUs. Haiku After the discontinuation of BeOS, an effort to create an open-source replacement began. Haiku (originally named OpenBeOS) reached its first milestone in September 2009 with the release of Haiku R1/Alpha 1. The x86 distribution is compatible with BeOS at both source and binary level. Like BeOS, it is written primarily in C++ and provides an object-oriented API. It is actively developed. IBM i (OS/400, i5/OS) IBM introduced OS/400 in 1988. This OS ran exclusively on the AS/400 platform. Renamed IBM i in 2008, this operating system and runs exclusively on Power Systems which also can run AIX and Linux. IBM i uses an object-oriented methodology and integrates a database (Db2 for i). The IBM i OS has a 128-bit unique identifier for each object. IBM OS/2 2.0 IBM's first priority based pre-emptive multitasking, graphical, windows-based operating system included an object-oriented user shell. It was designed for the Intel 80386 that used virtual 8086 mode with full 32-bit support and was released in 1992. ArcaOS, a new OS/2 based operating system initially called Blue Lion is being developed by Arca Noae. The first version was released in May 2017. IBM TopView TopView was an object-oriented operating environment that loaded on a PC on DOS, and then took control from DOS. At that point it effectively became an object-oriented operating system with an object-oriented API (TopView API). It was IBM's first multi-tasking, window based, object-oriented operating system for the PC led by David C. Morrill and released in February 1985. Java-based Given that Oracle's (formerly Sun Microsystems') Java is today one of the most dominant object-oriented languages, it is no surprise that Java-based operating systems have been attempted. In this area, ideally, the kernel would consist of the bare minimum needed to support a Java virtual machine (JVM). This is the only component of such an operating system that would have to be written in a language other than Java. Built on the JVM and basic hardware support, it would be possible to write the rest of the operating system in Java; even parts of the system that are more traditionally written in a lower-level language such as C, for example device drivers, can be written in Java. Examples of attempts at such an operating system include JavaOS, JOS, JNode, and JX. Lisp-based An object-oriented operating system written in the Lisp dialect Lisp Machine Lisp (and later Common Lisp) was developed at MIT. It was commercialized with Lisp Machines from Symbolics, Lisp Machines Inc. and Texas Instruments. Symbolics called their operating system Genera. It was developed with the Flavors object-oriented extension of Lisp, then with New Flavors, and then with the Common Lisp Object System (CLOS). Xerox developed several workstations with an operating system written in Interlisp-D. Interlisp-D provided object-oriented extensions like LOOPS and CLOS. Movitz and Mezzano are two more recent attempts at operating systems written in Common Lisp. Medos-2 Medos-2 is a single user, object-oriented operating system made for the Lilith line of workstations (processor: Advanced Micro Devices (AMD) 2901), developed in the early 1980s at ETH Zurich by Svend Erik Knudsen with advice from Niklaus Wirth. It is built entirely from modules of the programming language Modula-2. It was succeeded at ETH Zurich by the Oberon system, and a variant named Excelsior was developed for the Kronos workstation, by the Academy of Sciences of the Soviet Union, Siberian branch, Novosibirsk Computing Center, Modular Asynchronous Developable Systems (MARS) project, Kronos Research Group (KRG). Microsoft Singularity Singularity is an experimental operating system based on Microsoft's .NET Framework. It is comparable to Java-based operating systems. Microsoft Windows NT Windows NT is a family of operating systems (including Windows 7, 8, Phone 8, 8.1, Windows 10, Xbox) produced by Microsoft, the first version of which was released in July 1993. It is a high-level programming language-based, processor-independent, multiprocessing, multi-user operating system. It is best described as object-based rather than object-oriented as it does not include the full inheritance properties of object-oriented languages. The Object Manager is in charge of managing NT objects. As part of this responsibility, it maintains an internal namespace where various operating system components, device drivers, and Win32 programs can store and lookup objects. The NT Native API provides routines that allow user space (mode) programs to browse the namespace and query the status of objects located there, but the interfaces are undocumented. NT supports per-object (file, function, and role) access control lists allowing a rich set of security permissions to be applied to systems and services. WinObj is a Windows NT program that uses the NT Native API (provided by NTDLL.DLL) to access and display information on the NT Object Manager's name space. Component Object Model On the user mode side of Windows, the Component Object Model (COM) is an application binary interface standard for software components introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages. COM is the basis for several other Microsoft technologies and frameworks, including Object Linking and Embedding (OLE), OLE Automation, ActiveX, COM+, Distributed Component Object Model (DCOM), the Windows shell, DirectX, and Windows Runtime. OLE is a proprietary technology developed by Microsoft that allows embedding and linking to documents and other objects. On a technical level, an OLE object is any object that implements the IOleObject interface, possibly along with a wide range of other interfaces, depending on the object's needs. Its primary use is for managing compound documents, but it is also used for transferring data between different applications using drag and drop and clipboard operations. Compound File Binary Format Compound File Binary Format (CFBF) is a file format for storing many files and streams within one file on a disk. CFBF is developed by Microsoft and is an implementation of Microsoft COM Structured Storage. Structured storage is widely used as main file format in Microsoft Office applications including Microsoft Word, Microsoft Excel, Microsoft PowerPoint, Microsoft Access and is the basis of Advanced Authoring Format. Object Linking and Embedding Object Linking and Embedding (OLE) was part of a grander plan named Cairo, the code name for a project at Microsoft from 1991 to 1996. Its charter was to build technologies for a next generation operating system that would fulfill Bill Gates' vision of "information at your fingertips". Cairo never shipped, although parts of its technologies have since appeared in other products. The Windows 95 graphical user interface was based on the initial design work that was done on the Cairo user interface. The remaining component is the object-based file system. It was once planned to be implemented in the form of Windows Future Storage (WinFS) as part of Windows Vista. WinFS is the code name for data storage and management system project based on relational databases, running on the Windows NT file system (NTFS), which is object-oriented in that it can store the NT objects including its NT object identifier. Each NTFS object has an object identifier; a shortcut with a target that's on an NTFS volume also records the object identifier of the shortcut target, and the object identifier of the drive. WinFS was first demonstrated in 2003 as an advanced storage subsystem for the Microsoft Windows operating system, designed for persistence and management of structured, semi-structured, and unstructured data. WinFS development was cancelled in June 2006, with some of its technologies merged into other Microsoft products such as Microsoft SQL Server 2008 and Microsoft SharePoint. It was subsequently confirmed in an interview with Bill Gates that Microsoft planned to migrate applications like Windows Media Player, Windows Photo Gallery, Microsoft Office Outlook, etc., to use WinFS as the data storage back-end. NeXTSTEP During the late 1980s, Steve Jobs formed the computer company NeXT. One of NeXT's first tasks was to design an object-oriented operating system, NeXTSTEP. They did this by adding an object-oriented framework on Mach and BSD using the Objective-C language as a basis. It achieved a niche status in the computing market, notably used by Tim Berners-Lee developing the first implementation of the World Wide Web. NeXTStep later evolved into OpenStep and the Cocoa API on Mac OS X and iOS. OpenStep was provided as an API layer on many operating systems, namely HP-UX, NextStep, Solaris, and Windows. Oberon Oberon is a single user, object-oriented operating system made for the Ceres line of workstations (processor: National Semiconductor NS32000), developed in the later 1980s at ETH Zurich by Niklaus Wirth and Jürg Gutknecht. It is built entirely from modules of the programming language Oberon. A later evolution was named Active Object System (AOS), then renamed Bluebottle, then renamed A2. OOSMOS The Object-Oriented State Machine Operating System (OOSMOS), written in C, promotes object-oriented encapsulation and implements a full table-driven hierarchical state machine architecture. It generates C code directly from state charts drawn with the open source tool UMLet. OOSMOS also supports a unique feature call 'state threads' which allows a thread of execution per state. OOSMOS operates on a bare board or in cooperation with an existing operating system. ReactOS ReactOS is an open-source operating system intended to be binary compatible with application software and device drivers made for Microsoft Windows NT versions. Written from scratch, it aims to follow the architecture of Windows NT designed by Microsoft from the hardware level right through to the application level. This is not a Linux-based system, and shares none of the unix architecture. Self Self (programming language) was invented at Xerox PARC. It was then developed at Stanford University and Sun Microsystems. Smalltalk Smalltalk was invented at Xerox in the 1970s. The Smalltalk system is fully object-oriented and needs very little support by BIOS and the run-time system. Syllable Syllable makes heavy use of C++ and for that reason is often compared to BeOS. Symbolics Genera Genera from Symbolics is an operating system for Lisp machines written in ZetaLisp and Symbolics Common Lisp. It makes heavy use of Flavors (an early object-oriented extension to Lisp) and the Common Lisp Object System (CLOS). Development began in the mid 70s at MIT. Taligent Taligent was an object-oriented operating system project, begun by Apple Inc. and jointly developed with IBM in the 1990s. It was later spun off to an IBM subsidiary and transformed from an operating system to a programming environment. See also Operating system Object-oriented design Object-oriented programming Plan 9 from Bell Labs References External links Apertos Choices Hermes, former IBM project OOSMOS Rebol aspirations to displace the OS with the language environment Object-oriented programming Operating system technology

Operating System (OS)

MacOS macOS (; previously Mac OS X and later OS X) is a proprietary graphical operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and laptop computers it is the second most widely used desktop OS, after Microsoft Windows and ahead of Chrome OS. macOS succeeded the classic Mac OS, a Macintosh operating system with nine releases from 1984 to 1999. During this time, Apple cofounder Steve Jobs had left Apple and started another company, NeXT, developing the NeXTSTEP platform that would later be acquired by Apple to form the basis of macOS. The first desktop version, Mac OS X 10.0, was released in March 2001, with its first update, 10.1, arriving later that year. All releases from Mac OS X 10.5 Leopard and after are UNIX 03 certified, with an exception for OS X 10.7 Lion. Apple's mobile operating system, iOS, has been considered a variant of macOS. A prominent part of macOS's original brand identity was the use of Roman numeral X, pronounced "ten" as in Mac OS X and also the iPhone X, as well as code naming each release after species of big cats, or places within California. Apple shortened the name to "OS X" in 2012 and then changed it to "macOS" in 2016 to align with the branding of Apple's other operating systems, iOS, watchOS, and tvOS. After sixteen distinct versions of macOS 10, macOS Big Sur was presented as version 11 in 2020, and macOS Monterey was presented as version 12 in 2021. macOS has supported three major processor architectures, beginning with PowerPC-based Macs in 1999. In 2006, Apple transitioned to the Intel architecture with a line of Macs using Intel Core processors. In 2020, Apple began the Apple silicon transition, using self-designed, 64-bit ARM-based Apple M1 processors on new Mac computers. History Development The heritage of what would become macOS had originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, before being launched in 1989. The kernel of NeXTSTEP is based upon the Mach kernel, which was originally developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from parts of BSD. Its graphical user interface was built on top of an object-oriented GUI toolkit using the programming language. Throughout the early 1990s, Apple had tried to create a "next-generation" OS to succeed its classic Mac OS through the Taligent, Copland and Gershwin projects, but all were eventually abandoned. This led Apple to purchase NeXT in 1996, allowing NeXTSTEP, then called OPENSTEP, to serve as the basis for Apple's next generation operating system. This purchase also led to Steve Jobs returning to Apple as an interim, and then the permanent CEO, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be adopted by Apple's primary market of home users and creative professionals. The project was first code named "Rhapsody" and then officially named Mac OS X. Mac OS X Mac OS X was originally presented as the tenth major version of Apple's operating system for Macintosh computers; until 2020, versions of macOS retained the major version number "10". The letter "X" in Mac OS X's name refers to the number 10, a Roman numeral, and Apple has stated that it should be pronounced "ten" in this context. However, it is also commonly pronounced like the letter "X". Previous Macintosh operating systems (versions of the classic Mac OS) were named using Arabic numerals, as with Mac OS 8 and Mac OS 9. As of 2020 and 2021, Apple reverted to Arabic numeral versioning for successive releases, macOS 11 Big Sur and macOS 12 Monterey, as they have done for the iPhone 11 and iPhone 12 following the iPhone X. The first version of Mac OS X, Mac OS X Server 1.0, was a transitional product, featuring an interface resembling the classic Mac OS, though it was not compatible with software designed for the older system. Consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API; many could also be run directly through the Classic Environment with a reduction in performance. The consumer version of Mac OS X was launched in 2001 with Mac OS X 10.0. Reviews were variable, with extensive praise for its sophisticated, glossy Aqua interface, but criticizing it for sluggish performance. With Apple's popularity at a low, the makers of several classic Mac applications such as FrameMaker and PageMaker declined to develop new versions of their software for Mac OS X. Ars Technica columnist John Siracusa, who reviewed every major OS X release up to 10.10, described the early releases in retrospect as 'dog-slow, feature poor' and Aqua as 'unbearably slow and a huge resource hog'. Apple rapidly developed several new releases of Mac OS X. Siracusa's review of version 10.3, Panther, noted "It's strange to have gone from years of uncertainty and vaporware to a steady annual supply of major new operating system releases." Version 10.4, Tiger, reportedly shocked executives at Microsoft by offering a number of features, such as fast file searching and improved graphics processing, that Microsoft had spent several years struggling to add to Windows with acceptable performance. As the operating system evolved, it moved away from the classic Mac OS, with applications being added and removed. Considering music to be a key market, Apple developed the iPod music player and music software for the Mac, including iTunes and GarageBand. Targeting the consumer and media markets, Apple emphasized its new "digital lifestyle" applications such as the iLife suite, integrated home entertainment through the Front Row media center and the Safari web browser. With increasing popularity of the internet, Apple offered additional online services, including the .Mac, MobileMe and most recently iCloud products. It later began selling third-party applications through the Mac App Store. Newer versions of Mac OS X also included modifications to the general interface, moving away from the striped gloss and transparency of the initial versions. Some applications began to use a brushed metal appearance, or non-pinstriped title bar appearance in version 10.4. In Leopard, Apple announced a unification of the interface, with a standardized gray-gradient window style. In 2006, the first Intel Macs released used a specialized version of Mac OS X 10.4 Tiger. A key development for the system was the announcement and release of the iPhone from 2007 onwards. While Apple's previous iPod media players used a minimal operating system, the iPhone used an operating system based on Mac OS X, which would later be called "iPhone OS" and then iOS. The simultaneous release of two operating systems based on the same frameworks placed tension on Apple, which cited the iPhone as forcing it to delay Mac OS X 10.5 Leopard. However, after Apple opened the iPhone to third-party developers its commercial success drew attention to Mac OS X, with many iPhone software developers showing interest in Mac development. In 2007, Mac OS X 10.5 Leopard was the sole release with universal binary components, allowing installation on both Intel Macs and select PowerPC Macs. It is also the final release with PowerPC Mac support. Mac OS X 10.6 Snow Leopard was the first version of OS X to be built exclusively for Intel Macs, and the final release with 32-bit Intel Mac support. The name was intended to signal its status as an iteration of Leopard, focusing on technical and performance improvements rather than user-facing features; indeed it was explicitly branded to developers as being a 'no new features' release. Since its release, several OS X or macOS releases (namely OS X Mountain Lion, OS X El Capitan, macOS High Sierra, and macOS Monterey) follow this pattern, with a name derived from its predecessor, similar to the 'tick–tock model' used by Intel. In two succeeding versions, Lion and Mountain Lion, Apple moved some applications to a highly skeuomorphic style of design inspired by contemporary versions of iOS while simplifying some elements by making controls such as scroll bars fade out when not in use. This direction was, like brushed metal interfaces, unpopular with some users, although it continued a trend of greater animation and variety in the interface previously seen in design aspects such as the Time Machine backup utility, which presented past file versions against a swirling nebula, and the glossy translucent dock of Leopard and Snow Leopard. In addition, with Mac OS X 10.7 Lion, Apple ceased to release separate server versions of Mac OS X, selling server tools as a separate downloadable application through the Mac App Store. A review described the trend in the server products as becoming "cheaper and simpler... shifting its focus from large businesses to small ones." OS X In 2012, with the release of OS X 10.8 Mountain Lion, the name of the system was shortened from Mac OS X to OS X. That year, Apple removed the head of OS X development, Scott Forstall, and design was changed towards a more minimal direction. Apple's new user interface design, using deep color saturation, text-only buttons and a minimal, 'flat' interface, was debuted with iOS 7 in 2013. With OS X engineers reportedly working on iOS 7, the version released in 2013, OS X 10.9 Mavericks, was something of a transitional release, with some of the skeuomorphic design removed, while most of the general interface of Mavericks remained unchanged. The next version, OS X 10.10 Yosemite, adopted a design similar to iOS 7 but with greater complexity suitable for an interface controlled with a mouse. From 2012 onwards, the system has shifted to an annual release schedule similar to that of iOS. It also steadily cut the cost of updates from Snow Leopard onwards, before removing upgrade fees altogether from 2013 onwards. Some journalists and third-party software developers have suggested that this decision, while allowing more rapid feature release, meant less opportunity to focus on stability, with no version of OS X recommendable for users requiring stability and performance above new features. Apple's 2015 update, OS X 10.11 El Capitan, was announced to focus specifically on stability and performance improvements. macOS In 2016, with the release of macOS 10.12 Sierra, the name was changed from OS X to macOS to align it with the branding of Apple's other primary operating systems: iOS, watchOS, and tvOS. macOS 10.12 Sierra's main features are the introduction of Siri to macOS, Optimized Storage, improvements to included applications, and greater integration with Apple's iPhone and Apple Watch. The Apple File System (APFS) was announced at Apple's annual Worldwide Developers Conference (WWDC) in June 2016 as a replacement for HFS+, a highly criticized file system. Apple previewed macOS 10.13 High Sierra at WWDC 2017, before releasing it later that year. When running on solid state drives, it uses APFS, rather than HFS+. Its successor, macOS 10.14 Mojave, was released in 2018, adding a dark user interface option and a dynamic wallpaper setting. It was succeeded by macOS 10.15 Catalina in 2019, which replaces iTunes with separate apps for different types of media, and introduces the Catalyst system for porting iOS apps. In 2020, Apple previewed macOS 11 Big Sur at the WWDC 2020. This was the first increment in the primary version number of macOS since the release of Mac OS X Public Beta in 2000; updates to macOS 11 were given 11.x numbers, matching the version numbering scheme used by Apple's other operating systems. Big Sur brought major changes to the UI and was the first version to run on the ARM instruction set. The new numbering system was continued in 2021 with macOS 12 Monterey. Architecture At macOS's core is a POSIX-compliant operating system built on top of the XNU kernel, with standard Unix facilities available from the command line interface. Apple has released this family of software as a free and open source operating system named Darwin. On top of Darwin, Apple layered a number of components, including the Aqua interface and the Finder, to complete the GUI-based operating system which is macOS. With its original introduction as Mac OS X, the system brought a number of new capabilities to provide a more stable and reliable platform than its predecessor, the classic Mac OS. For example, pre-emptive multitasking and memory protection improved the system's ability to run multiple applications simultaneously without them interrupting or corrupting each other. Many aspects of macOS's architecture are derived from OPENSTEP, which was designed to be portable, to ease the transition from one platform to another. For example, NeXTSTEP was ported from the original 68k-based NeXT workstations to x86 and other architectures before NeXT was purchased by Apple, and OPENSTEP was later ported to the PowerPC architecture as part of the Rhapsody project. Prior to macOS High Sierra, and on drives other than solid state drives (SSDs), the default file system is HFS+, which it inherited from the classic Mac OS. Operating system designer Linus Torvalds has criticized HFS+, saying it is "probably the worst file system ever", whose design is "actively corrupting user data". He criticized the case insensitivity of file names, a design made worse when Apple extended the file system to support Unicode. The Darwin subsystem in macOS manages the file system, which includes the Unix permissions layer. In 2003 and 2005, two Macworld editors expressed criticism of the permission scheme; Ted Landau called misconfigured permissions "the most common frustration" in macOS, while Rob Griffiths suggested that some users may even have to reset permissions every day, a process which can take up to 15 minutes. More recently, another Macworld editor, Dan Frakes, called the procedure of repairing permissions vastly overused. He argues that macOS typically handles permissions properly without user interference, and resetting permissions should only be tried when problems emerge. The architecture of macOS incorporates a layered design: the layered frameworks aid rapid development of applications by providing existing code for common tasks. Apple provides its own software development tools, most prominently an integrated development environment called Xcode. Xcode provides interfaces to compilers that support several programming languages including C, C++, Objective-C, and Swift. For the Mac transition to Intel processors, it was modified so that developers could build their applications as a universal binary, which provides compatibility with both the Intel-based and PowerPC-based Macintosh lines. First and third-party applications can be controlled programmatically using the AppleScript framework, retained from the classic Mac OS, or using the newer Automator application that offers pre-written tasks that do not require programming knowledge. Software compatibility Apple offered two main APIs to develop software natively for macOS: Cocoa and Carbon. Cocoa was a descendant of APIs inherited from OPENSTEP with no ancestry from the classic Mac OS, while Carbon was an adaptation of classic Mac OS APIs, allowing Mac software to be minimally rewritten to run natively on Mac OS X. The Cocoa API was created as the result of a 1993 collaboration between NeXT Computer and Sun Microsystems. This heritage is highly visible for Cocoa developers, since the "NS" prefix is ubiquitous in the framework, standing variously for NeXTSTEP or NeXT/Sun. The official OPENSTEP API, published in September 1994, was the first to split the API between Foundation and ApplicationKit and the first to use the "NS" prefix. Traditionally, Cocoa programs have been mostly written in Objective-C, with Java as an alternative. However, on July 11, 2005, Apple announced that "features added to Cocoa in Mac OS X versions later than 10.4 will not be added to the Cocoa-Java programming interface." macOS also used to support the Java Platform as a "preferred software package"—in practice this means that applications written in Java fit as neatly into the operating system as possible while still being cross-platform compatible, and that graphical user interfaces written in Swing look almost exactly like native Cocoa interfaces. Since 2014, Apple has promoted its new programming language Swift as the preferred language for software development on Apple platforms. Apple's original plan with macOS was to require all developers to rewrite their software into the Cocoa APIs. This caused much outcry among existing Mac developers, who threatened to abandon the platform rather than invest in a costly rewrite, and the idea was shelved. To permit a smooth transition from Mac OS 9 to Mac OS X, the Carbon Application Programming Interface (API) was created. Applications written with Carbon were initially able to run natively on both classic Mac OS and Mac OS X, although this ability was later dropped as Mac OS X developed. Carbon was not included in the first product sold as Mac OS X: the little-used original release of Mac OS X Server 1.0, which also did not include the Aqua interface. Apple limited further development of Carbon from the release of Leopard onwards and announced that Carbon applications would not run at 64-bit. A number of macOS applications continued to use Carbon for some time afterwards, especially ones with heritage dating back to the classic Mac OS and for which updates would be difficult, uneconomic or not necessary. This included Microsoft Office up to Office 2016, and Photoshop up to CS5. Early versions of macOS could also run some classic Mac OS applications through the Classic Environment with performance limitations; this feature was removed from 10.5 onwards and all Macs using Intel processors. Because macOS is POSIX compliant, many software packages written for the other Unix-like systems including Linux can be recompiled to run on it, including much scientific and technical software. Third-party projects such as Homebrew, Fink, MacPorts and pkgsrc provide pre-compiled or pre-formatted packages. Apple and others have provided versions of the X Window System graphical interface which can allow these applications to run with an approximation of the macOS look-and-feel. The current Apple-endorsed method is the open-source XQuartz project; earlier versions could use the X11 application provided by Apple, or before that the XDarwin project. Applications can be distributed to Macs and installed by the user from any source and by any method such as downloading (with or without code signing, available via an Apple developer account) or through the Mac App Store, a marketplace of software maintained by Apple through a process requiring the company's approval. Apps installed through the Mac App Store run within a sandbox, restricting their ability to exchange information with other applications or modify the core operating system and its features. This has been cited as an advantage, by allowing users to install apps with confidence that they should not be able to damage their system, but also as a disadvantage due to blocking the Mac App Store's use for professional applications that require elevated privileges. Applications without any code signature cannot be run by default except from a computer's administrator account. Apple produces macOS applications. Some are included with macOS and some sold separately. This includes iWork, Final Cut Pro, Logic Pro, iLife, and the database application FileMaker. Numerous other developers also offer software for macOS. In 2018, Apple introduced an application layer, reportedly codenamed Marzipan, to port iOS apps to macOS. macOS Mojave included ports of four first-party iOS apps including Home and News, and it was announced that the API would be available for third-party developers to use from 2019. Hardware compatibility Tools such as XPostFacto and patches applied to the installation media have been developed by third parties to enable installation of newer versions of macOS on systems not officially supported by Apple. This includes a number of pre-G3 Power Macintosh systems that can be made to run up to and including Mac OS X 10.2 Jaguar, all G3-based Macs which can run up to and including Tiger, and sub-867 MHz G4 Macs can run Leopard by removing the restriction from the installation DVD or entering a command in the Mac's Open Firmware interface to tell the Leopard Installer that it has a clock rate of 867 MHz or greater. Except for features requiring specific hardware such as graphics acceleration or DVD writing, the operating system offers the same functionality on all supported hardware. As most Mac hardware components, or components similar to those, since the Intel transition are available for purchase, some technology-capable groups have developed software to install macOS on non-Apple computers. These are referred to as Hackintoshes, a portmanteau of the words "hack" and "Macintosh". This violates Apple's EULA (and is therefore unsupported by Apple technical support, warranties etc.), but communities that cater to personal users, who do not install for resale and profit, have generally been ignored by Apple. These self-made computers allow more flexibility and customization of hardware, but at a cost of leaving the user more responsible for their own machine, such as on matter of data integrity or security. Psystar, a business that attempted to profit from selling macOS on non-Apple certified hardware, was sued by Apple in 2008. PowerPC–Intel transition In April 2002, eWeek announced a rumor that Apple had a version of Mac OS X code-named Marklar, which ran on Intel x86 processors. The idea behind Marklar was to keep Mac OS X running on an alternative platform should Apple become dissatisfied with the progress of the PowerPC platform. These rumors subsided until late in May 2005, when various media outlets, such as The Wall Street Journal and CNET, announced that Apple would unveil Marklar in the coming months. On June 6, 2005, Steve Jobs announced in his keynote address at WWDC that Apple would be making the transition from PowerPC to Intel processors over the following two years, and that Mac OS X would support both platforms during the transition. Jobs also confirmed rumors that Apple had versions of Mac OS X running on Intel processors for most of its developmental life. Intel-based Macs would run a new recompiled version of OS X along with Rosetta, a binary translation layer which enables software compiled for PowerPC Mac OS X to run on Intel Mac OS X machines. The system was included with Mac OS X versions up to version 10.6.8. Apple dropped support for Classic mode on the new Intel Macs. Third party emulation software such as Mini vMac, Basilisk II and SheepShaver provided support for some early versions of Mac OS. A new version of Xcode and the underlying command-line compilers supported building universal binaries that would run on either architecture. PowerPC-only software is supported with Apple's official emulation software, Rosetta, though applications eventually had to be rewritten to run properly on the newer versions released for Intel processors. Apple initially encouraged developers to produce universal binaries with support for both PowerPC and Intel. PowerPC binaries suffer a performance penalty when run on Intel Macs through Rosetta. Moreover, some PowerPC software, such as kernel extensions and System Preferences plugins, are not supported on Intel Macs at all. Some PowerPC applications would not run on macOS at all. Plugins for Safari need to be compiled for the same platform as Safari, so when Safari is running on Intel, it requires plug-ins that have been compiled as Intel-only or universal binaries, so PowerPC-only plug-ins will not work. While Intel Macs can run PowerPC, Intel, and universal binaries, PowerPC Macs support only universal and PowerPC builds. Support for the PowerPC platform was dropped following the transition. In 2009, Apple announced at WWDC that Mac OS X 10.6 Snow Leopard would drop support for PowerPC processors and be Intel-only. Rosetta continued to be offered as an optional download or installation choice in Snow Leopard before it was discontinued with Mac OS X 10.7 Lion. In addition, new versions of Mac OS X first- and third-party software increasingly required Intel processors, including new versions of iLife, iWork, Aperture and Logic Pro. Intel–ARM transition Rumors of Apple shifting Macs to the ARM processors used by iOS devices began circulating as early as 2011, and ebbed and flowed throughout the 2010s. Rumors intensified in 2020, when numerous reports announced that the company would announce its shift to its custom processors at WWDC. Apple officially announced its shift to processors designed in-house on June 22, 2020, at WWDC 2020, with the transition planned to last for two years. The first release of macOS to support ARM is macOS Big Sur. The change in processor architecture allows Macs with ARM processors to be able to run natively with iOS and iPadOS apps. Features Aqua user interface One of the major differences between the classic Mac OS and the current macOS was the addition of Aqua, a graphical user interface with water-like elements, in the first major release of Mac OS X. Every window element, text, graphic, or widget is drawn on-screen using spatial anti-aliasing technology. ColorSync, a technology introduced many years before, was improved and built into the core drawing engine, to provide color matching for printing and multimedia professionals. Also, drop shadows were added around windows and isolated text elements to provide a sense of depth. New interface elements were integrated, including sheets (dialog boxes attached to specific windows) and drawers, which would slide out and provide options. The use of soft edges, translucent colors, and pinstripes, similar to the hardware design of the first iMacs, brought more texture and color to the user interface when compared to what Mac OS 9 and Mac OS X Server 1.0's "Platinum" appearance had offered. According to Siracusa, the introduction of Aqua and its departure from the then conventional look "hit like a ton of bricks." Bruce Tognazzini (who founded the original Apple Human Interface Group) said that the Aqua interface in Mac OS X 10.0 represented a step backwards in usability compared with the original Mac OS interface. Third-party developers started producing skins for customizable applications and other operating systems which mimicked the Aqua appearance. To some extent, Apple has used the successful transition to this new design as leverage, at various times threatening legal action against people who make or distribute software with an interface the company says is derived from its copyrighted design. Apple has continued to change aspects of the macOS appearance and design, particularly with tweaks to the appearance of windows and the menu bar. Since 2012, Apple has sold many of its Mac models with high-resolution Retina displays, and macOS and its APIs have extensive support for resolution-independent development on supporting high-resolution displays. Reviewers have described Apple's support for the technology as superior to that on Windows. The human interface guidelines published by Apple for macOS are followed by many applications, giving them consistent user interface and keyboard shortcuts. In addition, new services for applications are included, which include spelling and grammar checkers, special characters palette, color picker, font chooser and dictionary; these global features are present in every Cocoa application, adding consistency. The graphics system OpenGL composites windows onto the screen to allow hardware-accelerated drawing. This technology, introduced in version 10.2, is called Quartz Extreme, a component of Quartz. Quartz's internal imaging model correlates well with the Portable Document Format (PDF) imaging model, making it easy to output PDF to multiple devices. As a side result, PDF viewing and creating PDF documents from any application are built-in features. Reflecting its popularity with design users, macOS also has system support for a variety of professional video and image formats and includes an extensive pre-installed font library, featuring many prominent brand-name designs. Components The Finder is a file browser allowing quick access to all areas of the computer, which has been modified throughout subsequent releases of macOS. Quick Look has been part of the Finder since version 10.5. It allows for dynamic previews of files, including videos and multi-page documents without opening any other applications. Spotlight, a file searching technology which has been integrated into the Finder since version 10.4, allows rapid real-time searches of data files; mail messages; photos; and other information based on item properties (metadata) or content. macOS makes use of a Dock, which holds file and folder shortcuts as well as minimized windows. Apple added Exposé in version 10.3 (called Mission Control since version 10.7), a feature which includes three functions to help accessibility between windows and desktop. Its functions are to instantly display all open windows as thumbnails for easy navigation to different tasks, display all open windows as thumbnails from the current application, and hide all windows to access the desktop. FileVault is optional encryption of the user's files with the 128-bit Advanced Encryption Standard (AES-128). Features introduced in version 10.4 include Automator, an application designed to create an automatic workflow for different tasks; Dashboard, a full-screen group of small applications called desktop widgets that can be called up and dismissed in one keystroke; and Front Row, a media viewer interface accessed by the Apple Remote. Sync Services allows applications to access a centralized extensible database for various elements of user data, including calendar and contact items. The operating system then managed conflicting edits and data consistency. All system icons are scalable up to 512×512 pixels as of version 10.5 to accommodate various places where they appear in larger size, including for example the Cover Flow view, a three-dimensional graphical user interface included with iTunes, the Finder, and other Apple products for visually skimming through files and digital media libraries via cover artwork. That version also introduced Spaces, a virtual desktop implementation which enables the user to have more than one desktop and display them in an Exposé-like interface; an automatic backup technology called Time Machine, which allows users to view and restore previous versions of files and application data; and Screen Sharing was built in for the first time. In more recent releases, Apple has developed support for emoji characters by including the proprietary Apple Color Emoji font. Apple has also connected macOS with social networks such as Twitter and Facebook through the addition of share buttons for content such as pictures and text. Apple has brought several applications and features that originally debuted in iOS, its mobile operating system, to macOS in recent releases, notably the intelligent personal assistant Siri, which was introduced in version 10.12 of macOS. Multilingual support There are 39 system languages available in macOS for the user at the moment of installation; the system language is used throughout the entire operating system environment. Input methods for typing in dozens of scripts can be chosen independently of the system language. Recent updates have added increased support for Chinese characters and interconnections with popular social networks in China. Updating methods macOS can be updated using the Software Update preference pane in System Preferences or the softwareupdate command line utility. Until OS X 10.8 Mountain Lion, a separate Software Update application performed this functionality. In Mountain Lion and later, this was merged into the Mac App Store application, although the underlying update mechanism remains unchanged and is fundamentally different from the download mechanism used when purchasing an App Store application. In macOS 10.14 Mojave, the updating function was moved again to the Software Update preference pane. Release history Timeline of versions With the exception of Mac OS X Server 1.0 and the original public beta, OS X versions were named after big cats until OS X 10.9 Mavericks, when Apple switched to using California locations. Prior to its release, Mac OS X 10.0 was code named "Cheetah" internally at Apple, and Mac OS X 10.1 was code named internally as "Puma". After the immense buzz surrounding Mac OS X 10.2, codenamed "Jaguar", Apple's product marketing began openly using the code names to promote the operating system. Mac OS X 10.3 was marketed as "Panther", Mac OS X 10.4 as "Tiger", Mac OS X 10.5 as "Leopard", Mac OS X 10.6 as "Snow Leopard", Mac OS X 10.7 as "Lion", OS X 10.8 as "Mountain Lion", and OS X 10.9 as "Mavericks". "Panther", "Tiger" and "Leopard" are registered as trademarks of Apple, but "Cheetah", "Puma" and "Jaguar" have never been registered. Apple has also registered "Lynx" and "Cougar" as trademarks, though these were allowed to lapse. Computer retailer Tiger Direct sued Apple for its use of the name "Tiger". On May 16, 2005, a US federal court in the Southern District of Florida ruled that Apple's use did not infringe on Tiger Direct's trademark. Mac OS X Public Beta On September 13, 2000, Apple released a $29.95 "preview" version of Mac OS X, internally codenamed Kodiak, to gain feedback from users. The "PB", as it was known, marked the first public availability of the Aqua interface and Apple made many changes to the UI based on customer feedback. Mac OS X Public Beta expired and ceased to function in Spring 2001. Mac OS X 10.0 (Cheetah) On March 24, 2001, Apple released Mac OS X 10.0 (internally codenamed Cheetah). The initial version was slow, incomplete, and had very few applications available at launch, mostly from independent developers. While many critics suggested that the operating system was not ready for mainstream adoption, they recognized the importance of its initial launch as a base on which to improve. Simply releasing Mac OS X was received by the Macintosh community as a great accomplishment, for attempts to overhaul the Mac OS had been underway since 1996, and delayed by countless setbacks. Mac OS X 10.1 (Puma) Later that year on September 25, 2001, Mac OS X 10.1 (internally codenamed Puma) was released. It featured increased performance and provided missing features, such as DVD playback. Apple released 10.1 as a free upgrade CD for 10.0 users, in addition to the US$129 boxed version for people running Mac OS 9. It was discovered that the upgrade CDs were full install CDs that could be used with Mac OS 9 systems by removing a specific file; Apple later re-released the CDs in an actual stripped-down format that did not facilitate installation on such systems. On January 7, 2002, Apple announced that Mac OS X was to be the default operating system for all Macintosh products by the end of that month. Mac OS X 10.2 Jaguar On August 23, 2002, Apple followed up with Mac OS X 10.2 Jaguar, the first release to use its code name as part of the branding. It brought great raw performance improvements, a sleeker look, and many powerful user-interface enhancements (over 150, according to Apple ), including Quartz Extreme for compositing graphics directly on an ATI Radeon or Nvidia GeForce2 MX AGP-based video card with at least 16 MB of VRAM, a system-wide repository for contact information in the new Address Book, and an instant messaging client named iChat. The Happy Mac which had appeared during the Mac OS startup sequence for almost 18 years was replaced with a large grey Apple logo with the introduction of Mac OS X v10.2. Mac OS X 10.3 Panther Mac OS X v10.3 Panther was released on October 24, 2003. It significantly improved performance and incorporated the most extensive update yet to the user interface. Panther included as many or more new features as Jaguar had the year before, including an updated Finder, incorporating a brushed-metal interface, Fast user switching, Exposé (Window manager), FileVault, Safari, iChat AV (which added video conferencing features to iChat), improved Portable Document Format (PDF) rendering and much greater Microsoft Windows interoperability. Support for some early G3 computers such as "beige" Power Macs and "WallStreet" PowerBooks was discontinued. Mac OS X 10.4 Tiger Mac OS X 10.4 Tiger was released on April 29, 2005. Apple stated that Tiger contained more than 200 new features. As with Panther, certain older machines were no longer supported; Tiger requires a Mac with 256 MB and a built-in FireWire port. Among the new features, Tiger introduced Spotlight, Dashboard, Smart Folders, updated Mail program with Smart Mailboxes, QuickTime 7, Safari 2, Automator, VoiceOver, Core Image and Core Video. The initial release of the Apple TV used a modified version of Tiger with a different graphical interface and fewer applications and services. On January 10, 2006, Apple released the first Intel-based Macs along with the 10.4.4 update to Tiger. This operating system functioned identically on the PowerPC-based Macs and the new Intel-based machines, with the exception of the Intel release lacking support for the Classic environment. Mac OS X 10.5 Leopard Mac OS X 10.5 Leopard was released on October 26, 2007. It was called by Apple "the largest update of Mac OS X". It brought more than 300 new features. Leopard supports both PowerPC- and Intel x86-based Macintosh computers; support for the G3 processor was dropped and the G4 processor required a minimum clock rate of 867 MHz, and at least 512 MB of RAM to be installed. The single DVD works for all supported Macs (including 64-bit machines). New features include a new look, an updated Finder, Time Machine, Spaces, Boot Camp pre-installed, full support for 64-bit applications (including graphical applications), new features in Mail and iChat, and a number of new security features. Leopard is an Open Brand UNIX 03 registered product on the Intel platform. It was also the first BSD-based OS to receive UNIX 03 certification. Leopard dropped support for the Classic Environment and all Classic applications. It was the final version of Mac OS X to support the PowerPC architecture. Mac OS X 10.6 Snow Leopard Mac OS X 10.6 Snow Leopard was released on August 28, 2009. Rather than delivering big changes to the appearance and end user functionality like the previous releases of , Snow Leopard focused on "under the hood" changes, increasing the performance, efficiency, and stability of the operating system. For most users, the most noticeable changes were: the disk space that the operating system frees up after a clean install compared to Mac OS X 10.5 Leopard, a more responsive Finder rewritten in Cocoa, faster Time Machine backups, more reliable and user-friendly disk ejects, a more powerful version of the Preview application, as well as a faster Safari web browser. Snow Leopard only supported machines with Intel CPUs, required at least 1 GB of RAM, and dropped default support for applications built for the PowerPC architecture (Rosetta could be installed as an additional component to retain support for PowerPC-only applications). Snow Leopard also featured new 64-bit technology capable of supporting greater amounts of RAM, improved support for multi-core processors through Grand Central Dispatch, and advanced GPU performance with OpenCL. The 10.6.6 update introduced support for the Mac App Store, Apple's digital distribution platform for macOS applications. OS X 10.7 Lion OS X 10.7 Lion was released on July 20, 2011. It brought developments made in Apple's iOS, such as an easily navigable display of installed applications called Launchpad and a greater use of multi-touch gestures, to the Mac. This release removed Rosetta, making it incompatible with PowerPC applications. Changes made to the GUI include auto-hiding scrollbars that only appear when they are used, and Mission Control which unifies Exposé, Spaces, Dashboard, and full-screen applications within a single interface. Apple also made changes to applications: they resume in the same state as they were before they were closed, similar to iOS. Documents auto-save by default. OS X 10.8 Mountain Lion OS X 10.8 Mountain Lion was released on July 25, 2012. Following the release of Lion the previous year, it was the first of the annual rather than two-yearly updates to OS X (and later macOS), which also closely aligned with the annual iOS operating system updates. It incorporates some features seen in iOS 5, which include Game Center, support for iMessage in the new Messages messaging application, and Reminders as a to-do list app separate from iCal (which is renamed as Calendar, like the iOS app). It also includes support for storing iWork documents in iCloud. Notification Center, which makes its debut in Mountain Lion, is a desktop version similar to the one in iOS 5.0 and higher. Application pop-ups are now concentrated on the corner of the screen, and the Center itself is pulled from the right side of the screen. Mountain Lion also includes more Chinese features including support for Baidu as an option for Safari search engine, QQ, 163.com and 126.com services for Mail, Contacts and Calendar, Youku, Tudou and Sina Weibo are integrated into share sheets. Starting with Mountain Lion, Apple software updates (including the OS) are distributed via the App Store. This updating mechanism replaced the Apple Software Update utility. OS X 10.9 Mavericks OS X 10.9 Mavericks was released on October 22, 2013. It was a free upgrade to all users running Snow Leopard or later with a 64-bit Intel processor. Its changes include the addition of the previously iOS-only Maps and iBooks applications, improvements to the Notification Center, enhancements to several applications, and many under-the-hood improvements. OS X 10.10 Yosemite OS X 10.10 Yosemite was released on October 16, 2014. It features a redesigned user interface similar to that of iOS 7, intended to feature a more minimal, text-based 'flat' design, with use of translucency effects and intensely saturated colors. Apple's showcase new feature in Yosemite is Handoff, which enables users with iPhones running iOS 8.1 or later to answer phone calls, receive and send SMS messages, and complete unfinished iPhone emails on their Mac. As of OS X 10.10.3, Photos replaced iPhoto and Aperture. OS X 10.11 El Capitan OS X 10.11 El Capitan was released on September 30, 2015. Similar to Mac OS X 10.6 Snow Leopard, Apple described this release as emphasizing "refinements to the Mac experience" and "improvements to system performance". Refinements include public transport built into the Maps application, GUI improvements to the Notes application, adopting San Francisco as the system font for clearer legibility, and the introduction of System Integrity Protection. The Metal API, first introduced in iOS 8, was also included in this operating system for "all Macs since 2012". According to Apple, Metal accelerates system-level rendering by up to 50 percent, resulting in faster graphics performance for everyday apps. Metal also delivers up to 10 times faster draw call performance for more fluid experience in games and pro apps. macOS 10.12 Sierra macOS 10.12 Sierra was released to the public on September 20, 2016. New features include the addition of Siri, Optimized Storage, and updates to Photos, Messages, and iTunes. macOS 10.13 High Sierra macOS 10.13 High Sierra was released to the public on September 25, 2017. Like OS X El Capitan and OS X Mountain Lion, High Sierra is a refinement-based update having very few new features visible to the user, including updates to Safari, Photos, and Mail, among other changes. The major change under the hood is the switch to the Apple File System, optimized for the solid-state storage used in most new Mac computers. macOS 10.14 Mojave macOS 10.14 Mojave was released on September 24, 2018. The update introduced a system-wide dark mode and several new apps lifted from iOS, such as Apple News. It was the first version to require a GPU that supports Metal. Mojave also changed the system software update mechanism from the App Store (where it had been since OS X Mountain Lion) to a new panel in System Preferences. App updates remain in the App Store. macOS 10.15 Catalina macOS 10.15 Catalina was released on October 7, 2019. Updates included enhanced voice control, and bundled apps for music, video, and podcasts that together replace the functions of iTunes, and the ability to use an iPad as an external monitor. Catalina officially dropped support for 32-bit applications. macOS 11 Big Sur macOS Big Sur was announced during the WWDC keynote speech on June 22, 2020, and it was made available to the general public on November 12, 2020. This is the first time the major version number of the operating system has been incremented since the Mac OS X Public Beta in 2000. It brings ARM support, new icons, and aesthetic user interface changes to the system. macOS 12 Monterey macOS Monterey was announced during the WWDC keynote speech on June 7, 2021 and released on October 25, 2021, introducing Universal Control (which allows input devices to be used with multiple devices simultaneously), Focus (which allows selectively limiting notifications and alerts depending on user-defined user/work modes), Shortcuts (a task automation framework previously only available on iOS and iPadOS expected to replace Automator), a redesigned Safari Web browser, and updates and improvements to FaceTime. Reception Usage share As of July 2016, macOS is the second-most-active general-purpose desktop client operating system used on the World Wide Web following Microsoft Windows, with a 4.90% usage share according to statistics compiled by the Wikimedia Foundation. It is the second-most widely used desktop operating system (for web browsing), after Windows, and is estimated at approximately five times the usage of Linux (which has 1.01%). Usage share generally continues to shift away from the desktop and toward mobile operating systems such as iOS and Android. Malware and spyware In its earlier years, Mac OS X enjoyed a near-absence of the types of malware and spyware that have affected Microsoft Windows users. macOS has a smaller usage share compared to Windows. Worms, as well as potential vulnerabilities, were noted in 2006, which led some industry analysts and anti-virus companies to issue warnings that Apple's Mac OS X is not immune to malware. Increasing market share coincided with additional reports of a variety of attacks. In early 2011, Mac OS X experienced a large increase in malware attacks, and malware such as Mac Defender, MacProtector, and MacGuard was seen as an increasing problem for Mac users. At first, the malware installer required the user to enter the administrative password, but later versions installed without user input. Initially, Apple support staff were instructed not to assist in the removal of the malware or admit the existence of the malware issue, but as the malware spread, a support document was issued. Apple announced an OS X update to fix the problem. An estimated 100,000 users were affected. Apple releases security updates for macOS regularly, as well as signature files containing malware signatures for Xprotect, an anti-malware feature part of File Quarantine present since Mac OS X Snow Leopard. Promotion As a device company, Apple has mostly promoted macOS to sell Macs, with promotion of macOS updates focused on existing users, promotion at Apple Store and other retail partners, or through events for developers. In larger scale advertising campaigns, Apple specifically promoted macOS as better for handling media and other home-user applications, and comparing Mac OS X (especially versions Tiger and Leopard) with the heavy criticism Microsoft received for the long-awaited Windows Vista operating system. See also Dock (macOS) Classic Mac OS (1984–2001) Comparison of BSD operating systems Comparison of operating systems List of operating systems List of Macintosh software Macintosh operating systems References External links – official site macOS Support – official support page 1999 software Apple Inc. operating systems Apple Inc. software Computer-related introductions in 1999 Mach (kernel) X86-64 operating systems ARM operating systems

Operating System (OS)

Disk operating system A disk operating system (abbreviated DOS) is a computer operating system that resides on and can use a disk storage device, such as a floppy disk, hard disk drive, or optical disc. A disk operating system must provide a file system for organizing, reading, and writing files on the storage disk. Strictly speaking, this definition does not apply to current generations of operating systems, such as versions of Microsoft Windows in use, and is more appropriately used only for older generations of operating systems. Disk operating systems were available for mainframes, minicomputers, microprocessors and home computers and were usually loaded from the disks themselves as part of the boot process. History In the early days of computers, there were no disk drives, floppy disks or modern flash storage devices. Early storage devices such as delay lines, core memories, punched cards, punched tape, magnetic tape, and magnetic drums were used instead. And in the early days of microcomputers and home computers, paper tape or audio cassette tape (see Kansas City standard) or nothing were used instead. In the latter case, program and data entry was done at front panel switches directly into memory or through a computer terminal / keyboard, sometimes controlled by a BASIC interpreter in ROM; when power was turned off any information was lost. In the early 1960s, as disk drives became larger and more affordable, various mainframe and minicomputer vendors began introducing disk operating systems and modifying existing operating systems to exploit disks. Both hard disks and floppy disk drives require software to manage rapid access to block storage of sequential and other data. For most microcomputers, a disk drive of any kind was an optional peripheral; systems could be used with a tape drive or booted without a storage device at all. The disk operating system component of the operating system was only needed when a disk drive was used. By the time IBM announced the System/360 mainframes, the concept of a disk operating system was well established. Although IBM did offer Basic Programming Support (BPS/360) and TOS/360 for small systems, they were out of the mainstream and most customers used either DOS/360 or OS/360. Most home and personal computers of the late 1970s and 1980s used a disk operating system, most often with "DOS" in the name and simply referred to as "DOS" within their respective communities: CBM DOS for Commodore 8-bit systems, Atari DOS for the Atari 8-bit family, TRS-DOS for the TRS-80, Apple DOS and ProDOS for the Apple II, AmigaDOS for the Amiga, and MS-DOS for IBM PC compatibles. Usually, a disk operating system was loaded from a disk. Among the exceptions were Commodore, whose DOS resided on ROM chips in the disk drives. The Lt. Kernal hard disk subsystem for the Commodore 64 and Commodore 128 models stored its DOS on the disk, as is the case with modern systems, and loaded the DOS into RAM at boot time; the British BBC Micro's optional Disc Filing System, DFS, offered as a kit with a disk controller chip, a ROM chip, and a handful of logic chips, to be installed inside the computer. Disk operating systems that were extensions to the OS Apple DOS was the primary operating system for the Apple II series of computers, from 1979 with the introduction of the floppy disk drive, until 1983 when it was replaced by ProDOS. Commodore DOS was used on 8-bit Commodore computers such as the Commodore 64. Unlike most other DOS systems, it was integrated into the disk drives, not loaded into the computer's own memory. Atari DOS was used by the Atari 8-bit family of computers. The Atari OS only offered low-level disk-access, so an extra layer called DOS was booted from a floppy and offered higher level functions such as filesystems. Third-party replacements for Atari DOS were also available: DOS XL, SpartaDOS, MyDOS, TurboDOS, Top-DOS. MSX-DOS for the MSX computer standard. Initial version, released in 1984, was nothing but MS-DOS 1.0 ported to Z80; but in 1988 it evolved to version 2, offering facilities such as subdirectories, memory management and environment strings. The MSX-DOS kernel resided in ROM (built-in on the disk controller) so basic file access capacity was available even without the command interpreter, by using BASIC extended commands. Disc Filing System (DFS) This was an optional component for the Acorn BBC Micro, offered as a kit with a disk controller chip, a ROM chip, and a handful of logic chips, to be installed inside the computer Advanced Disc Filing System (ADFS) was a successor to Acorn's DFS. AMSDOS for the Amstrad CPC computers. GDOS and G+DOS, for the +D and DISCiPLE disk interfaces for the ZX Spectrum. Disk operating systems that were the main OSs Some disk operating systems were the operating systems for the entire computer system. The Burroughs Master Control Program (MCP) for the B5000 originally ran from a drum, but starting with the B5500 it ran from a disk. It is the basis for the MCP on the B6500, B7500 and their successor systems. The SIPROS, Chippewa Operating System (COS), SCOPE, MACE and KRONOS operating systems on the Control Data Corporation (CDC) 6000 series and 7600 were all disk operating systems. KRONOS evolved into NOS and SCOPE evolved into NOS/BE. The GECOS operating system for the GE 600 family of mainframe computers (it later became GCOS). The IBM Basic Operating System/360 (BOS/360), Disk Operating System/360 (DOS/360) and Operating System/360 (OS/360) were standard for all but the smallest System/360 installations. BOS is gone, DOS has evolved into z/VSE and OS has evolved into z/OS. The DOS-11 operating system for DEC PDP-11 minicomputers. CP/M was a disk operating system--even though it was not named as such--used as the main or alternate operating system for numerous microcomputers of the 1970s and 1980s. TRSDOS was the operating system for the TRS-80 line of computers from Tandy. MS-DOS for IBM PC compatibles with Intel x86 CPUs. It started as 86-DOS, which was modeled on CP/M, and then itself served as the basis for Microsoft's MS-DOS, and was rebranded by IBM as IBM PC DOS until 1993. Various compatible systems were later produced by different organizations, starting with DR-DOS in 1988. See also Live CD References Notes Disk operating systems

Operating System (OS)

OS/VS1 Operating System/Virtual Storage 1, or OS/VS1, is a discontinued IBM mainframe computer operating system designed to be run on IBM System/370 hardware. It was the successor to the Multiprogramming with a Fixed number of Tasks (MFT) option of System/360's operating system OS/360. OS/VS1, in comparison to its predecessor, supported virtual memory (then called virtual storage). OS/VS1 was generally available during the 1970s and 1980s, and it is no longer supported by IBM. Description OS/VS1 was OS/360 MFT II with a single virtual address space; by comparison, OS/VS2 SVS was OS/360 MVT with a single virtual address space. OS/VS1 was often installed on mid-range IBM mainframe systems, such as the System/370 Model 145 and, later, the System/370 Model 148. OS/VS1 was intended to manage a medium-sized work load (for the 1970s) consisting only of batch processing applications, running within a fixed number of operating system partitions via the batch job management system Job Entry Subsystem 1 (JES1). This was in contrast to OS/VS2 which was intended to handle larger work loads consisting of batch applications, online interactive users (using the Time Sharing Option, or TSO), or a combination of both. However, OS/VS1 could, and often did, support interactive applications and users by running IBM's CICS transaction processing monitor as a job within one of its partitions. Installation and modification of OS/VS1 was accomplished via IBM's cumbersome System Generation (SYSGEN) process. Remote Entry Services (RES) OS/VS1 included a replacement for OS/360 RJE. It allowed submission and retrieval of jobs by 2770, 2780 and 3780 terminals and by workstation programs included with OS/VS1 for, e.g., 1130. RES included Remote Terminal Access Method and a closer integration with Job Management than what RJE had. IBM upgrades OS/VS1 went through seven product releases. IBM enhanced OS/VS1 Release 7 with four releases of the IBM OS/VS1 Basic Programming Extensions (BPE), product 5662-257. BPE provides support for new 1980s hardware, such as 3380 Direct Access Storage, and for VM handshaking between VTAM and VM/VTAM Communications Network Application (VCNA). IBM announced the last BPE release, OS/VS1 Basic Programming Extensions Release 4, on September 15, 1983, with planned general availability in March 1984. IBM announced the end of functional enhancements to OS/VS1 in 1984. IBM recommended OS/VS1 installations migrate to MVS/370 or MVS/XA. To assist with the migration to MVS/XA, IBM made the VM/XA Migration Aid. It allowed installations to run OS/VS1 and MVS/XA simultaneously on the same machine, as guests of a third systemVM/XA. This way, the new MVS/XA system could be tested while the old production OS/VS1 system was still in use. On January 24, 1989, IBM announced the intention to withdraw OS/VS1 and OS/VS1 BPE from marketing effective April 24, 1989, and to discontinue service effective February 28, 1990. Time-sharing Although IBM's Time Sharing Option (TSO) required VS2, customers with a 370/145 or 370/148 had other time-sharing options. One combination was VM/CMS for time sharing, and a guest "machine" running OS/360 MFT II for batch. Conversational Remote Job Entry Optional component of OS/360 MFT II, OS/360 MVT and OS/VS1, CRJE allowed the user at a line-mode terminal to edit text datasets, submit jobs and access job output. TONE for VS1 A non-IBM time-sharing product named TONE (TSO-like, for VS1 / VS ONE) was marketed by Tone Software Co. References Further reading Functional structure of IBM virtual storage operating systems, Part I: Influences of dynamic address translation on operating system technology, by M. A. Auslander and J. F. Jaffe, IBM Systems Journal, Volume 12 (1973), No 4, Page 368 OS/VS1 Concepts and Philosophies, by T. F. Wheeler, Jr., IBM Systems Journal, Volume 13 (1974), No 3, Page 213 The job entry subsystem of OS/VS1, by J. H. Baily, J. A. Howard, and T. J. Szczygielski, IBM Systems Journal, Volume 13 (1974), No 3, Page 253 (The OS/V1 job entry subsystem was named JES1) IBM mainframe operating systems 1972 software

Operating System (OS)

Operations support system Operations support systems (OSS), operational support systems in British usage, or Operation System (OpS) in NTT, are computer systems used by telecommunications service providers to manage their networks (e.g., telephone networks). They support management functions such as network inventory, service provisioning, network configuration and fault management. Together with business support systems (BSS), they are used to support various end-to-end telecommunication services. BSS and OSS have their own data and service responsibilities. The two systems together are often abbreviated OSS/BSS, BSS/OSS or simply B/OSS. The acronym OSS is also used in a singular form to refer to all the Operations Support Systems viewed as a whole system. Different subdivisions of OSS have been proposed by the TM Forum, industrial research labs, or OSS vendors. In general, an OSS covers at least the following five functions: Network management systems Service delivery Service fulfillment, including the network inventory, activation and provisioning Service assurance Customer care History Before about 1970, many OSS activities were performed by manual administrative processes. However, it became obvious that much of this activity could be replaced by computers. In the next 5 years or so, the telephone companies created a number of computer systems (or software applications) which automated much of this activity. This was one of the driving factors for the development of the Unix operating system and the C programming language. The Bell System purchased their own product line of PDP-11 computers from Digital Equipment Corporation for a variety of OSS applications. OSS systems used in the Bell System include AMATPS, CSOBS, EADAS, Remote Memory Administration System (RMAS), Switching Control Center System (SCCS), Service Evaluation System (SES), Trunks Integrated Record Keeping System (TIRKS), and many more. OSS systems from this era are described in the Bell System Technical Journal, Bell Labs Record, and Telcordia Technologies (now part of Ericsson) SR-2275. Many OSS systems were initially not linked to each other and often required manual intervention. For example, consider the case where a customer wants to order a new telephone service. The ordering system would take the customer's details and details of their order, but would not be able to configure the telephone exchange directly—this would be done by a switch management system. Details of the new service would need to be transferred from the order handling system to the switch management system—and this would normally be done by a technician re-keying the details from one screen into another—a process often referred to as "swivel chair integration". This was clearly another source of inefficiency, so the focus for the next few years was on creating automated interfaces between the OSS applications—OSS integration. Cheap and simple OSS integration remains a major goal of most telecom companies. Architecture A lot of the work on OSS has been centered on defining its architecture. Put simply, there are four key elements of OSS: Processes the sequence of events Data the information that is acted upon Applications the components that implement processes to manage data Technology how we implement the applications During the 1990s, new OSS architecture definitions were done by the ITU Telecommunication Standardization Sector (ITU-T) in its Telecommunications Management Network (TMN) model. This established a 4-layer model of TMN applicable within an OSS: Business Management Level (BML) Service Management Level (SML) Network Management Level (NML) Element Management Level (EML) A fifth level is mentioned at times being the elements themselves, though the standards speak of only four levels. This was a basis for later work. Network management was further defined by the ISO using the FCAPS model—Fault, Configuration, Accounting, Performance and Security. This basis was adopted by the ITU-T TMN standards as the Functional model for the technology base of the TMN standards M.3000 – M.3599 series. Although the FCAPS model was originally conceived and is applicable for an IT enterprise network, it was adopted for use in the public networks run by telecommunication service providers adhering to ITU-T TMN standards. A big issue of network and service management is the ability to manage and control the network elements of the access and core networks. Historically, many efforts have been spent in standardization fora (ITU-T, 3GPP) in order to define standard protocol for network management, but with no success and practical results. On the other hand IETF SNMP protocol (Simple Network Management Protocol) has become the de facto standard for internet and telco management, at the EML-NML communication level. From 2000 and beyond, with the growth of the new broadband and VoIP services, the management of home networks is also entering the scope of OSS and network management. DSL Forum TR-069 specification has defined the CPE WAN Management Protocol (CWMP), suitable for managing home networks devices and terminals at the EML-NML interface. TM Forum The TM Forum, formerly the TeleManagement Forum, is an international membership organization of communications service providers and suppliers to the communications industry. While OSS is generally dominated by proprietary and custom technologies, TM Forum promotes standards and frameworks in OSS and BSS. By 2005, developments in OSS architecture were the results of the TM Forum's New Generation Operations Systems and Software (NGOSS) program, which was established in 2000. This established a set of principles that OSS integration should adopt, along with a set of models that provide standardized approaches. NGOSS was renamed Frameworx. Frameworx models An information model (the Shared Information/Data model, or SID) – now more commonly referred to as the Information Framework, A process model (the enhanced Telecom Operation Map, or eTOM) – now more commonly known as the Business Process Framework, An application model (the Telecom Applications Map) – now known as the Application Framework, an architecture (the Technology Neutral Architecture) and a lifecycle model. The TM Forum describes Frameworx as an architecture that is: "loosely coupled" distributed component based The components interact through a common communications vehicle (using an information exchange infrastructure; e.g., EAI, Web Services, EJB). The behavior can be controlled through the use of process management and/or policy management to orchestrate the functionality provided by the services offered by the components. The early focus of the TM Forum's NGOSS work was on building reference models to support a business stakeholder view on process, information and application interaction. Running in parallel were activities that supported an implementation stakeholder view on interface specifications to provide access to OSS capability (primarily MTNM). The MTNM work evolved into a set of Web Services providing Multi-Technology Operations System Interfaces MTOSI. Most recently, the OSS through Java initiative (OSS/J) joined the TMF to provide NGOSS-based BSS/OSS APIs. Ongoing work - Open Digital Architecture (ODA) Open Digital Architecture (ODA) offers an industry-agreed blueprint, language and set of key design principles to follow. It will provide pragmatic pathways for the journey from maintaining monolithic, legacy software solutions, towards managing nimble, cloud based capabilities that can be orchestrated using AI. It is a reference architecture that maps TM Forum’s Open APIs against technical and business platform functions. See also Business support system COSMOS (telecommunications) Loop maintenance operations system OA&M Service Evaluation System Switching Control Center System References External links Video: What is OSS/BSS? TM Forum OSS through Java initiative OSS News Review OSS Observer landing page of Analysys Mason Pipeline Magazine InsideTelephony OSS/BSS (2017.05.20 via Wayback Machine) Billing & OSS World OSS Line Telecommunications OSS and BSS Telcordia SR-2275 Network management Telecommunications systems

Operating System (OS)

Apple GS/OS GS/OS is an operating system developed by Apple Computer for its Apple IIGS personal computer that uses the ProDOS file system. It provides facilities for accessing the file system, controlling input/output devices, loading and running program files, and a system allowing programs to handle interrupts and signals. GS/OS was included as a component of Apple IIGS System Software versions 4.0 through 6.0.1. GS/OS, unlike its predecessor, is written entirely in 16-bit code and was the first true 16-bit operating system for the IIGS. GS/OS includes a facility known as file system translators (FSTs) which allows it to support multiple on-disk file systems in a manner transparent to application programs, a feature not found in ProDOS or most other microcomputer operating systems at the time. It was usually used with the ProDOS file system (which was the only one from which it could be booted), but GS/OS also supports a variety of other file systems, including the Hierarchical File System used by the Mac OS. Other file system translators, in addition to ProDOS and HFS, include those for MS-DOS, High Sierra/ISO-9660, Apple DOS 3.3, and Pascal, albeit read-only (full read/write support had been planned but never completed). Another advantage of GS/OS over its predecessor, the ProDOS 16 operating system, is that it was written in 16-bit code for the 65816 processor used in the IIGS, rather than primarily in 8-bit 6502 machine code that does not take advantage of the IIGS's unique features. It also extends the ProDOS file system to provide for resource forks on files similar to those used on the Apple Macintosh, which allows for programs to be written in a more flexible way. The big change from the previous versions of ProDOS is that GS/OS offers vast speed optimizations (loading time, disk access, screen updates) and incorporates many features of other Apple operating systems, including Apple III Apple SOS, the Macintosh System 5, as well as concepts and features that would later appear in future Macintosh System Software releases. In particular, in addition to a Finder, loadable fonts, plug-in device drivers (modem, printer, etc.), GS/OS also offers a thermometer progress display, AppleShare support, File System Translators for accessing foreign file formats, disk caching and the ability to use resource forks. A command-line development environment called APW (Apple Programmer's Workshop) is available; much like the Macintosh Programmer's Workshop. Releases Source: ProDOS 16 (GS/OS predecessor) 1986 – System 1.0 (ProDOS 16 v1.0), System 1.1 (ProDOS 16 v1.1) 1987 – System 2.0 (ProDOS 16 v1.2), System 3.1 (ProDOS 16 v1.3) 1988 – System 3.2 (ProDOS 16 v1.6) GS/OS 1988 – System 4.0 (GS/OS v2.0) 1989 – System 5.0 (GS/OS v3.0), System 5.0.1 (GS/OS v3.0), System 5.0.2 (GS/OS v3.0) 1990 – System 5.0.3 (GS/OS v3.03) 1991 – System 5.0.4 (GS/OS v3.03) 1992 – System 6.0 (GS/OS v4.01) 1993 – System 6.0.1 (GS/OS v4.02) Unofficial versions 2015 – System 6.0.2 (GS/OS v4.02), System 6.0.3 (GS/OS v4.02) 2017 – System 6.0.4 (GS/OS v4.02) See also Apple DOS Apple II Apple IIGS Juiced.GS – The last remaining Apple II publication KansasFest – An annual convention for Apple II users Macintosh Finder ProDOS References External links Apple IIgs GS/OS 6.0.1 Screenshots and details GS/OS at the Apple II History Museum A2Central.com – Apple II news and downloads Apple II software Apple Inc. operating systems Disk operating systems Discontinued operating systems Window-based operating systems

Operating System (OS)

UNOS (operating system) UNOS is the first, now discontinued, 32-bit Unix-like real-time operating system (RTOS) with real-time extensions. It was developed by Jeffery Goldberg, MS. who left Bell Labs after using Unix and became VP of engineering for Charles River Data Systems (CRDS), now defunct. UNOS was written to capitalize on the first 32-bit microprocessor, the Motorola 68k central processing unit (CPU). CRDS sold a UNOS based 68K system, and sold porting services and licenses to other manufacturers who had embedded CPUs. History Jeff Goldberg created an experimental OS using only eventcounts for synchronization, that allowed a preemptive kernel, for a Charles River Data Systems (CRDS) PDP-11. CRDS hired Goldberg to create UNOS and began selling it in 1981. UNOS was written for the Motorola 68000 series processors. While compatible with Version 7 Unix, it is also an RTOS. CRDS supported it on the company's Universe 68 computers, as did Motorola's Versabus systems. CRDS's primary market was OEMs embedding the CRDS unit within a larger pile of hardware, often requiring better real-time response than Unix could deliver. UNOS has a cleaner kernel interface than UNIX in 1981. There was e.g., a system call to obtain ps information instead of reading /dev/kmem. UNOS required memory protection, with the 68000 using an MMU developed by CRDS; and only used Motorola MMUs after UNOS 7 on the 68020 (CRDS System CP20) (using the MC68851 PMMU). UNOS was written in the programming languages C and assembly language, and supported Fortran, COBOL, Pascal, and Business Basic. Limits UNOS from CRDS never supported paged virtual memory and multiprocessor support had not been built in from the start, so the kernel remained mostly single-threaded on the few multiprocessor systems built. A UNOS variant enhanced by H. Berthold AG under the name vBertOS added demanded page loading and paged processes in 1984, but was given up in favor of SunOS because of the missing GUI and the missing networking code in Spring 1985, when Berthold imported the first Sun to Europe. References Discontinued operating systems Embedded operating systems Real-time operating systems Unix variants 68k architecture

Operating System (OS)

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system. IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax, and capabilities. Beginning in 1988 with DR-DOS, several competing products were released for the x86 platform, and MS-DOS went through eight versions, until development ceased in 2000. Initially, MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in ever greater sizes and formats, along with added feature support for newer processors and rapidly evolving computer architectures. Ultimately, it was the key product in Microsoft's development from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI. History MS-DOS was a renamed form of 86-DOS owned by Seattle Computer Products, written by Tim Paterson. Development of 86-DOS took only six weeks, as it was basically a clone of Digital Research's CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M: an improved disk sector buffering logic, and the introduction of FAT12 instead of the CP/M filesystem. This first version was shipped in August 1980. Microsoft, which needed an operating system for the IBM Personal Computer, hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for in July of the same year. Microsoft kept the version number, but renamed it MS-DOS. They also licensed MS-DOS 1.10/1.14 to IBM, which, in August 1981, offered it as PC DOS 1.0 as one of three operating systems for the IBM 5150 or the IBM PC. Within a year, Microsoft licensed MS-DOS to over 70 other companies. It was designed to be an OS that could run on any 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, and with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers (the DOS BIOS), minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, and installable device drivers for other devices loaded and integrated at boot time. The OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and a standard Microsoft kernel, which they would typically supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, and there is a major distinction between an IBM-compatible (or ISA) machine and an MS-DOS [compatible] machine. Some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could run software written exclusively for MS-DOS without dependence on the peripheral hardware of the IBM PC architecture. This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O, and indeed the same design philosophy is embodied in Windows NT (see Hardware Abstraction Layer). However, in MS-DOS's early days, the greater speed attainable by programs through direct control of hardware was of particular importance, especially for games, which often pushed the limits of their contemporary hardware. Very soon an IBM-compatible architecture became the goal, and before long all 8086-family computers closely emulated IBM's hardware, and only a single version of MS-DOS for a fixed hardware platform was needed for the market. This version is the version of MS-DOS that is discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to the systems they were designed for, and in any case were very similar in function and capability to some standard version for the IBM PC—often the same-numbered version, but not always, since some OEMs used their own proprietary version numbering schemes (e.g. labeling later releases of MS-DOS 1.x as 2.0 or vice versa)—with a few notable exceptions. Microsoft omitted multi-user support from MS-DOS because Microsoft's Unix-based operating system, Xenix, was fully multi-user. The company planned, over time, to improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the Motorola 68000, Zilog Z8000, and the LSI-11; they would be upwardly compatible with Xenix, which Byte in 1983 described as "the multi-user MS-DOS of the future". Microsoft advertised MS-DOS and Xenix together, listing the shared features of its "single-user OS" and "the multi-user, multi-tasking, UNIX-derived operating system", and promising easy porting between them. After the breakup of the Bell System, however, AT&T Computer Systems started selling UNIX System V. Believing that it could not compete with AT&T in the Unix market, Microsoft abandoned Xenix, and in 1987 transferred ownership of Xenix to the Santa Cruz Operation (SCO). On March 25, 2014, Microsoft made the code to SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11 available to the public under the Microsoft Research License Agreement, which makes the code source-available, but not open source as defined by Open Source Initiative or Free Software Foundation standards. Microsoft would later re-license the code under the MIT License on September 28, 2018, making these versions free software. As an April Fool's Day joke in 2015, Microsoft Mobile launched a Windows Phone application called MS-DOS Mobile which was presented as a new mobile operating system and worked similar to MS-DOS. Versions Microsoft licensed or released versions of MS-DOS under different names like Lifeboat Associates "Software Bus 86" a.k.a. SB-DOS, COMPAQ-DOS, NCR-DOS or Z-DOS before it eventually enforced the MS-DOS name for all versions but the IBM one, which was originally called "IBM Personal Computer DOS", later shortened to IBM PC DOS. (Competitors released compatible DOS systems such as DR DOS and PTS-DOS that could also run DOS applications.) In the former Eastern bloc, MS-DOS derivatives named DCP () 3.20 and 3.30 (DCP 1700, DCP 3.3) and WDOS existed in the late 1980s. They were produced by the East German electronics manufacturer VEB Robotron. The following versions of MS-DOS were released to the public: MS-DOS 1.x Version 1.24 (OEM) – basis for IBM's Personal Computer DOS 1.1 Version 1.25 (OEM) – basis for non-IBM OEM versions of MS-DOS, including SCP MS-DOS 1.25 Compaq-DOS 1.12, a Compaq OEM version of MS-DOS 1.25; Release date: November, 1983 TI BOOT V. 1.13, a Texas Instruments OEM version of MS-DOS; Release date: August, 1983 Zenith Z-DOS 1.19, a Zenith OEM version of MS-DOS 1.25 Zenith Z-DOS/MS-DOS release 1.01, version 1.25, a Zenith OEM version of MS-DOS; Release date: May, 1983 MS-DOS 2.x Support for IBM's XT 10 MB hard disk drives, support up to 16 MB or 32 MB FAT12 formatted hard disk drives depending on the formatting tool shipped by OEMs, user installable device drivers, tree-structure filing system, Unix-like inheritable redirectable file handles, non-multitasking child processes an improved Terminate and Stay Resident (TSR) API, environment variables, device driver support, FOR and GOTO loops in batch files, ANSI.SYS. Version 2.0 (OEM), First version to support 5.25-inch, 180 KB and 360 KB floppy disks; Release date: October 1983 Version 2.02 (OEM, Compaq); Release date: November 1983 Version 2.05 (OEM, international support); Release date: October 1983 Version 2.1 (OEM, IBM only) Version 2.11 (OEM) Altos MS-DOS 2.11, an Altos OEM version of MS-DOS 2.11 for the ACT-86C ITT Corporation ITT-DOS 2.11 Version 2 (MS-DOS 2.11 for the ITT XTRA Personal Computer); Release date: July 1985 Toshiba MS-DOS 2.11 in ROM drive for the model T1000 laptop TeleVideo PC DOS 2.11, a TeleVideo OEM version of MS-DOS 2.11 Olivetti M19 came with MS-DOS 2.11 Version 2.13 (OEM, Zenith); Release date: July 1984 Version 2.2 (OEM, with Hangeul support) Version 2.25 (OEM, with Hangeul and Kanji support) Version 2.3 (used on the Toshiba Pasopia 16) MS-DOS 3.x Version 3.0 (OEM) – First version to support 5.25-inch, 1.2 MB floppy drives and diskettes, FAT16 partitions up to 32 MB; Release date: April, 1985 Version 3.1 (OEM) – Support for Microsoft Networks through an IFS layer, remote file and printer API Version 3.2 (OEM) – First version to support 3.5-inch, 720 kB floppy drives and diskettes and XCOPY. Version 3.10 (OEM, Multitech); Release date: May, 1986 Version 3.20 – First retail release (non-OEM); Release date: July, 1986 Version 3.21 (OEM / non-OEM); Release date: May, 1987 Version 3.22 (OEM) – (HP 95LX) Version 3.25 (OEM) Version 3.3 (OEM) – First version to support 3.5-inch, 1.44 MB floppy drives and diskettes, extended and logical partitions, directory tree copying with XCOPY, improved support for internationalization (COUNTRY.SYS), networked file flush operations Version 3.3a (OEM) Version 3.30; Release date: February, 1988 Version 3.30A (OEM, DTK); Release date: July, 1987 Version 3.30T (OEM, Tandy); Release date: July, 1990 Version 3.31 (Compaq OEM only) – supports FAT16B with partitions larger than 32 MiB; Release date: November, 1989 MS-DOS 4.0 / MS-DOS 4.x MS-DOS 4.0 (multitasking) and MS-DOS 4.1 A separate branch of development with additional multitasking features, released between 3.2 and 3.3, and later abandoned. It is unrelated to any later versions, including versions 4.00 and 4.01 listed below MS-DOS 4.x (IBM-developed) – includes a graphical/mouse interface. It had many bugs and compatibility issues. Version 4.00 (OEM) – First version with builtin IBM/Microsoft support of a hard disk partitions greater than 32 MB and up to a maximum size of 2 GB, FASTOPEN/FASTSEEK, DOSSHELL, could use EMS for the disk buffers and provided EMS drivers and emulation for 386 compatible processors; Release date: October, 1988 Version 4.01 (OEM) – Microsoft rewritten Version 4.00 released under MS-DOS label but not IBM PC DOS. First version to introduce volume serial number when formatting hard disks and floppy disks (Disk duplication also and when using SYS to make a floppy disk or a partition of a hard drive bootable); Release date: April, 1989 Version 4.01a (OEM) MS-DOS 5.x Version 5.0 (Retail) – includes a full-screen text editor. A number of bugs required re issue. First version to support 3.5-inch, 2.88 MB floppy drives and diskettes. The SHARE command was not needed anymore for old DOS 1.x style FCB file API to partitions over 32 MB. First version to get the HIMEM.SYS driver and load portions of the operating system into the upper memory area and high memory area. Support up to four DOS primary partitions although FDISK cannot create more than one. AST Premium Exec DOS 5.0 (OEM) a version for the AST Premium Exec series of notebooks with various extensions, including improved load-high and extended codepage support Version 5.0a (Retail) – With this release, IBM and Microsoft versions diverge. Version 5.50 (Windows NTVDM) – All Windows NT 32-bit versions ship with files from DOS 5.0 MS-DOS 6.x Version 6.0 (Retail) – Online help through QBASIC. Disk compression, upper memory optimization and antivirus included. Version 6.2 – SCANDISK as replacement for CHKDSK. Fix serious bugs in DBLSPACE. Version 6.21 (Retail) – Stacker-infringing DBLSPACE removed. Version 6.22 (Retail) – New DRVSPACE compression. MS-DOS 7/8 (as part of Windows 9x) Windows 95's first retail release included support for VFAT long file names when run in a Windows Virtual-8086 box and 32-bits signed integer errorlevel. New editor. JO.SYS is an alternative filename of the IO.SYS kernel file and used as such for "special purposes". JO.SYS allows booting from either CD-ROM drive or hard disk. Last version to recognize only the first 8.4 GB of a hard disk. The VER internal command reports the Windows version 4.00.950, applications through the MS-DOS API would be reported a version number of 7.00. Windows 95's OEM Service Release 2, through Windows 98 Second Edition, added support for the FAT32 file system, and was the last version that could boot to the command line from a hard disk. The VER internal command reports the Windows version 4.00.1111, 4.10.1998, or 4.10.2222 depending on the version of Windows, while applications through the API would report version 7.10. Windows Me was the last version based on MS-DOS, and DOS mode was significantly altered in this release. Booting from the hard disk to a command line only was no longer permitted, AUTOEXEC.BAT and CONFIG.SYS files were no longer loaded nor parsed before loading the Windows GUI; booting from floppy disk was still permitted to allow for emergency recovery and this version is included in Windows XP and later versions for creating MS-DOS Startup Disks. The VER internal command reports the Windows version 4.90.3000, or 5.1 when created from newer versions of Windows. Applications requesting the version through the API would report version 8.00. Microsoft DOS was released through the OEM channel, until Digital Research released DR-DOS 5.0 as a retail upgrade. With PC DOS 5.00.1, the IBM-Microsoft agreement started to end, and IBM entered the retail DOS market with IBM DOS 5.00.1, 5.02, 6.00 and PC DOS 6.1, 6.3, 7, 2000 and 7.1. Localized versions Localized versions of MS-DOS existed for different markets. While Western issues of MS-DOS evolved around the same set of tools and drivers just with localized message languages and differing sets of supported codepages and keyboard layouts, some language versions were considerably different from Western issues and were adapted to run on localized PC hardware with additional BIOS services not available in Western PCs, support multiple hardware codepages for displays and printers, support DBCS, alternative input methods and graphics output. Affected issues include Japanese (DOS/V), Korean, Arabic (ADOS 3.3/5.0), Hebrew (HDOS 3.3/5.0), Russian (RDOS 4.01/5.0) as well as some other Eastern European versions of DOS. Competition On microcomputers based on the Intel 8086 and 8088 processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from Digital Research, whose CP/M operating system had inspired MS-DOS. In fact, there remains controversy as to whether QDOS was more or less plagiarized from early versions of CP/M code. Digital Research released CP/M-86 a few months after MS-DOS, and it was offered as an alternative to MS-DOS and Microsoft's licensing requirements, but at a higher price. Executable programs for CP/M-86 and MS-DOS were not interchangeable with each other; many applications were sold in both MS-DOS and CP/M-86 versions until MS-DOS became preponderant (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS originally supported the simple .COM, which was modeled after a similar but binary-incompatible format known from CP/M-80. CP/M-86 instead supported a relocatable format using the file extension .CMD to avoid name conflicts with CP/M-80 and MS-DOS .COM files. MS-DOS version 1.0 added a more advanced relocatable .EXE executable file format. Most of the machines in the early days of MS-DOS had differing system architectures and there was a certain degree of incompatibility, and subsequently vendor lock-in. Users who began using MS-DOS with their machines were compelled to continue using the version customized for their hardware, or face trying to get all of their proprietary hardware and software to work with the new system. In the business world the 808x-based machines that MS-DOS was tied to faced competition from the Unix operating system which ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called Xenix. In the emerging world of home users, a variety of other computers based on various other processors were in serious competition with the IBM PC: the Apple II, early Apple Macintosh, the Commodore 64 and others did not use the 808x processor; many 808x machines of different architectures used custom versions of MS-DOS. At first all these machines were in competition. In time the IBM PC hardware configuration became dominant in the 808x market as software written to communicate directly with the PC hardware without using standard operating system calls ran much faster, but on true PC-compatibles only. Non-PC-compatible 808x machines were too small a market to have fast software written for them alone, and the market remained open only for IBM PCs and machines that closely imitated their architecture, all running either a single version of MS-DOS compatible only with PCs, or the equivalent IBM PC DOS. Most clones cost much less than IBM-branded machines of similar performance, and became widely used by home users, while IBM PCs had a large share of the business computer market. Microsoft and IBM together began what was intended as the follow-on to MS-DOS/PC DOS, called OS/2. When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that "DOS is Dead" and stating that version 4 was the last full release. OS/2 was designed for efficient multi-tasking and offered a number of advanced features that had been designed together with similar look and feel; it was seen as the legitimate heir to the "kludgy" DOS platform. MS-DOS had grown in spurts, with many significant features being taken or duplicated from Microsoft's other products and operating systems. MS-DOS also grew by incorporating, by direct licensing or feature duplicating, the functionality of tools and utilities developed by independent companies, such as Norton Utilities, PC Tools (Microsoft Anti-Virus), QEMM expanded memory manager, Stacker disk compression, and others. During the period when Digital Research was competing in the operating system market some computers, like Amstrad PC1512, were sold with floppy disks for two operating systems (only one of which could be used at a time), MS-DOS and CP/M-86 or a derivative of it. Digital Research produced DOS Plus, which was compatible with MS-DOS 2.11, supported CP/M-86 programs, had additional features including multi-tasking, and could read and write disks in CP/M and MS-DOS format. While OS/2 was under protracted development, Digital Research released the MS-DOS compatible DR DOS 5.0, which included features only available as third-party add-ons for MS-DOS. Unwilling to lose any portion of the market, Microsoft responded by announcing the "pending" release of MS-DOS 5.0 in May 1990. This effectively killed most DR DOS sales until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR DOS 6.0, which sold well until the "pre-announcement" of MS-DOS 6.0 again stifled the sales of DR DOS. Microsoft had been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD (fear, uncertainty, and doubt) regarding DR DOS. For example, in October 1990, shortly after the release of DR DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in InfoWorld and PC Week. Brad Silverberg, then Vice President of Systems Software at Microsoft and general manager of its Windows and MS-DOS Business Unit, wrote a forceful letter to PC Week (November 5, 1990), denying that Microsoft was engaged in FUD tactics ("to serve our customers better, we decided to be more forthcoming about version 5.0") and denying that Microsoft copied features from DR DOS: "The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn't be surprising that DRI has heard some of the same requests from customers that we have." – (Schulman et al. 1994). The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Much of Microsoft's further contributions to OS/2 also went into creating a third GUI replacement for DOS, Windows NT. IBM, which had already been developing the next version of OS/2, carried on development of the platform without Microsoft and sold it as the alternative to DOS and Windows. Legal issues As a response to Digital Research's DR DOS 6.0, which bundled SuperStor disk compression, Microsoft opened negotiations with Stac Electronics, vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft part of the Stacker source code. Stac was unwilling to meet Microsoft's terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft's DoubleDisk, using it as the core for its DoubleSpace disk compression. MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had disk compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code. Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages in the Caldera v. Microsoft lawsuit. It was believed that the settlement ran in the order of $150 million, but was revealed in November 2009 with the release of the Settlement Agreement to be $280 million. Use of undocumented APIs Microsoft also used a variety of tactics in MS-DOS and several of their applications and development tools that, while operating perfectly when running on genuine MS-DOS (and PC DOS), would break when run on another vendor's implementation of DOS. Notable examples of this practice included: Microsoft's QuickPascal (released in early 1989) was the first MS product that checked for MS-DOS by modifying the program's Program Segment Prefix using undocumented DOS functions, and then checked whether or not the associated value changed in a fixed position within the DOS data segment (also undocumented). This check also made it into later MS products, including Microsoft QuickC v2.5, Programmer's Workbench and Microsoft C v6.0. The AARD code, a block of code in the windows launcher (WIN.COM) and a few other system files of Windows 3.1. It was XOR encrypted, self-modifying, and deliberately obfuscated, using various undocumented DOS structures and functions to determine whether or not Windows really was running on MS-DOS. In the beta versions, it displayed an "error" message if the test for genuine MS-DOS failed, prompting the user to abort or continue, with abort the default. In the final release version, the code still ran, but the message and prompt were disabled by an added flag byte, rendering it (probably) ineffectual. Note that the Windows 3.0 beta code only gave a warning that Windows would not operate properly on a "foreign" OS. It did, in fact, run just fine on DR DOS 6.0. Interrupt routines called by Windows to inform MS-DOS that Windows is starting/exiting, information that MS-DOS retained in an IN_WINDOWS flag, in spite of the fact that MS-DOS and Windows were supposed to be two separate products. Windows command-line interface All versions of Microsoft Windows have had an MS-DOS or MS-DOS-like command-line interface called MS-DOS Prompt which redirected input to MS-DOS and output from MS-DOS to the MS-DOS Prompt, or, in later versions, Command Prompt. This could run many DOS and variously Win32, OS/2 1.x and POSIX command-line utilities in the same command-line session, allowing piping between commands. The user interface, and the icon up to Windows 2000, followed the native MS-DOS interface. The Command Prompt introduced with Windows NT is not actually MS-DOS, but shares some commands with MS-DOS. Earlier versions of Windows The 16-bit versions of Windows (up to 3.11) ran as a Graphical User Interface (GUI) on top of MS-DOS. With Windows 95, 98, 98 SE and Me, the role of MS-DOS was reduced to a boot loader, with MS-DOS programs running in a virtual DOS machine within 32-bit Windows, with ability to boot directly into MS-DOS retained as a backward compatibility option for applications that required real mode access to the hardware, which was generally not possible within Windows. The command line accessed the DOS command line (usually COMMAND.COM) through a Windows module (WINOLDAP.MOD). Windows NT Windows NT-based operating systems boot through a kernel whose sole purpose is to load Windows. One cannot run Win32 applications in the loader system in the manner that OS/2, UNIX or consumer versions of Windows can launch character-mode sessions. The command session permits running various supported command-line utilities from Win32, MS-DOS, OS/2 1.x and POSIX. The emulators for MS-DOS, OS/2 and POSIX use the host's window in the same way that Win16 applications use the Win32 explorer. Using the host's window allows one to pipe output between emulations. The MS-DOS emulation takes place through the NTVDM (NT Virtual DOS Machine). This is a modified SoftPC (a former product similar to VirtualPC), running a modified MS-DOS 5 (NTIO.SYS and NTDOS.SYS). The output is handled by the console DLLs, so that the program at the prompt (CMD.EXE, 4NT.EXE, TCC.EXE), can see the output. 64-bit Windows has neither the DOS emulation, nor the DOS commands EDIT, DEBUG and EDLIN that come with 32-bit Windows. The DOS version returns 5.00 or 5.50, depending on which API function is used to determine it. Utilities from MS-DOS 5.00 run in this emulation without modification. The very early beta programs of NT show MS-DOS 30.00, but programs running in MS-DOS 30.00 would assume that OS/2 was in control. The OS/2 emulation is handled through OS2SS.EXE and OS2.EXE, and DOSCALLS.DLL. OS2.EXE is a version of the OS/2 shell (CMD.EXE), which passes commands down to the OS2SS.EXE, and input-output to the Windows NT shell. Windows 2000 was the last version of NT to support OS/2. The emulation is OS/2 1.30. POSIX is emulated through the POSIX shell, but no emulated shell; the commands are handled directly in CMD.EXE. The Command Prompt is often called the MS-DOS Prompt. In part, this was the official name for it in Windows 9x and early versions of Windows NT (NT 3.5 and earlier), and in part because the SoftPC emulation of DOS redirects output into it. Actually only COMMAND.COM and other 16-bit commands run in an NTVDM with AUTOEXEC.NT and CONFIG.NT initialisation determined by _DEFAULT.PIF, optionally permitting the use of Win32 console applications and internal commands with an NTCMDPROMPT directive. Win32 console applications use CMD.EXE as their command prompt shell. This confusion does not exist under OS/2 because there are separate DOS and OS/2 prompts, and running a DOS program under OS/2 will launch a separate DOS window to run the application. All versions of Windows for Itanium (no longer sold by Microsoft) and x86-64 architectures no longer include the NTVDM and can therefore no longer natively run DOS or 16-bit Windows applications. There are alternatives such as virtual machine emulators such as Microsoft's own Virtual PC, as well as VMware, DOSBox etc., unofficial compatibility layers such as NTVDMx64, OTVDM (WineVDM), Win3mu and others. End-of-life The introduction of Windows 3.0 in 1990, with an easy-to-use graphical user interface, marked the beginning of the end for the command-line driven MS-DOS. With the release of Windows 95 (and continuing in the Windows 9x product line through to Windows Me), an integrated version of MS-DOS was used for bootstrapping, troubleshooting, and backwards-compatibility with old DOS software, particularly games, and no longer released as a standalone product. In Windows 95, the DOS, called MS-DOS 7, can be booted separately, without the Windows GUI; this capability was retained through Windows 98 Second Edition. Windows Me removed the capability to boot its underlying MS-DOS 8.0 alone from a hard disk, but retained the ability to make a DOS boot floppy disk (called an "Emergency Boot Disk") and can be hacked to restore full access to the underlying DOS. On December 31, 2001, Microsoft declared all versions of MS-DOS 6.22 and older obsolete and stopped providing support and updates for the system. As MS-DOS 7.0 was a part of Windows 95, support for it also ended when Windows 95 extended support ended on December 31, 2001. As MS-DOS 7.10 and MS-DOS 8.0 were part of Windows 98 and Windows ME respectively, support ended when Windows 98 and ME extended support ended on on July 11, 2006, thus ending support and updates of MS-DOS from Microsoft. In contrast to the Windows 9x series, the Windows NT-derived 32-bit operating systems (Windows NT, 2000, XP and newer), developed alongside the 9x series, do not contain MS-DOS compatibility as a core component of the operating system nor do they rely on it for bootstrapping, as NT was not with the level of support for legacy MS-DOS and Win16 apps that Windows 9x was, but does provide limited DOS emulation called NTVDM (NT Virtual DOS Machine) to run DOS applications and provide DOS-like command prompt windows. 64-bit versions of Windows NT do not provide DOS emulation and cannot run DOS applications natively. Windows XP contains a copy of the Windows Me boot disk, stripped down to bootstrap only. This is accessible only by formatting a floppy as an "MS-DOS startup disk". Files like the driver for the CD-ROM support were deleted from the Windows Me bootdisk and the startup files (AUTOEXEC.BAT and CONFIG.SYS) no longer had content. This modified disk was the base for creating the MS-DOS image for Windows XP. Some of the deleted files can be recovered with an undelete tool. When booting up an MS-DOS startup disk made with Windows XP's format tool, the version number and the VER internal command reports as "Windows Millennium" and "5.1", respectively, and not as "MS-DOS 8.0" (which was used as the base for Windows Me but never released as a stand-alone product), though the API still says Version 8.0. When creating a DOS startup disk on Windows Vista, the files on the startup disk are dated April 18, 2005 but are otherwise unchanged, including the string "MS-DOS Version 8 Copyright 1981–1999 Microsoft Corp" inside COMMAND.COM. Windows 7, 8, and 8.1 can also create a MS-DOS startup disk. Starting with Windows 10, the ability to create a DOS startup disk has been removed and so either a virtual machine running MS-DOS or an older version (in a virtual machine or dual boot) must be used to format a floppy disk, or an image must be obtained from an external source. Other solutions include using DOS compatible alternatives, such as FreeDOS or even copying the required files and boot sector themselves. With Windows 11, the operating system does not support NTVDM as it's only 64-bit, thus removing any traces of MS-DOS from Windows and Microsoft. MS-DOS 6.22 was the last standalone version produced by Microsoft for Intel 8088, Intel 8086, and Intel 80286 processors, which remain available for download via their MSDN, volume license, and OEM license partner websites, for customers with valid login credentials. MS-DOS is still used in embedded x86 systems due to its simple architecture and minimal memory and processor requirements, though some current products have switched to the still-maintained open-source alternative FreeDOS. In 2018, Microsoft released the source code for MS-DOS 1.25 and 2.0 on GitHub. The purpose of this, according to Microsoft, is mainly for education and experimentation with historic operating systems and for new programmers to gain an understanding of how low-level software works, both historic and current. According to program manager Rich Turner, the other versions could not be open-sourced due to third-party licensing restrictions. Due to the historical nature of the software, Microsoft will not accept any pull requests to the code; only pull requests for modified and translated documentation will be accepted. Users, however, are allowed and fully encouraged to fork the repository containing the MS-DOS source code and make their own modifications, and do whatever they like with it. Legacy compatibility From 1983 onwards, various companies worked on graphical user interfaces (GUIs) capable of running on PC hardware. However, this required duplicated effort and did not provide much consistency in interface design (even between products from the same company). Later, in 1985, Microsoft Windows 1.0 was released as Microsoft's first attempt at providing a consistent user interface (for applications). The early versions of Windows ran on top of MS-DOS. At first Windows met with little success, but this was also true for most other companies' efforts as well, for example GEM. After version 3.0, Windows gained market acceptance. Windows 9x used MS-DOS to boot the Windows kernel in protected mode. Basic features related to the file system, such as long file names, were only available to DOS applications when running through Windows. Windows NT runs independently of DOS but includes NTVDM, a component for simulating a DOS environment for legacy applications. Related systems MS-DOS compatible systems include: IBM PC DOS DR DOS, Novell DOS, OpenDOS FreeDOS PTS-DOS ROM-DOS Microsoft manufactured IBM PC DOS for IBM. It and MS-DOS were identical products that eventually diverged starting with MS-DOS version 6.0. Digital Research did not follow Microsoft's version numbering scheme. For example, MS-DOS 4, released in July 1988, was followed by DR DOS 5.0 in May 1990. MS-DOS 5.0 came in April 1991, and DR DOS 6.0 was released the following June. These products are collectively referred to as "DOS", even though "Disk Operating System" is a generic term used on other systems unrelated to the x86 and IBM PC. "MS-DOS" can also be a generic reference to DOS on IBM PC compatible computers. Microsoft's control of the Windows platform, and their programming practices which intentionally made Windows appear as if it ran poorly on competing versions of DOS, crippled the ability of other DOS makers to continue to compete with MS-DOS. Digital Research had to release interim releases to circumvent Windows limitations inserted artificially, designed specifically to provide Microsoft with a competitive advantage. See also 4DOS – designed to replace the default command interpreter COMMAND.COM Bad command or file name DOSBox History of Microsoft Windows Towns OS – an MS-DOS adaptation by Fujitsu for FM Towns Tao ExDOS – commercial solution for DOS software on new Windows systems. Win32 console – an environment provided by Windows operating systems to support character-mode applications Notes References External links MS-DOS Source MS-DOS 1.1 and MS-DOS 2.0 Source Code on GitHub Current License Agreement Policies for MS-DOS and Windows Tim Paterson on DOS – Paterson wrote the QDOS OS DOSBox, a multiplatform DOS emulator Archive.Org: MS Dos Emulator 1981 software Discontinued Microsoft operating systems Disk operating systems DOS variants Floppy disk-based operating systems Microcomputer software Microsoft free software Free software operating systems Proprietary operating systems Software using the MIT license Assembly language software Formerly proprietary software

Operating System (OS)

Business Operating System (software) The Business Operating System, or BOS, was initially developed as an early cross-platform operating system, originally produced for Intel 8080 and Motorola 6800 computers, then redeveloped for actual businesses and business models. The technology began subsequently for Zilog Z80-based computers, and then later for most microcomputers of the 1980s, then developed into a premium automated software solution for Investors and Asset Managers alike. CAP Ltd, a British company and at the time one of the world's largest Information Technology consulting firms, developed BOS. CAP designed BOS and BOS applications for platform-independence. Via a management buyout (MBO) in 1981, BOS was spun off to three interlinked companies, MPSL (MicroProducts Software Ltd) which looked after the sales and marketing of BOS, MPPL (MicroProducts Programming Ltd) which looked after both the development of BOS and various horizontal software packages, and MicroProducts Training Ltd. BOS was distributed on a global basis, mainly to the United States and British Commonwealth, by a variety of independent and MPSL-owned companies. A popular version was implemented on the Sage/Stride 68000 family based computers, and sold well in Australia. The Sage itself was initially developed using UCSD Pascal and p-code, so it fitted well with the basic BOS design. The small BOS dealer/distributor network and its command-line interface structure met its demise when graphical user interface operating systems became prevalent. The redevelopment of which, in 2013, was integrated with a graphical user interface, GUI, in order to provide a "simple to use" solution, which "learned" from its user's input. MPSL developed numerous products for BOS, generally targeting the horizontal markets, leaving the vertical markets (i.e. niche) to independent software vendors ISV. Examples of MPSL developed software include BOS/Finder (database), BOS/Planner (spreadsheet), BOS/Writer (word processor) and BOS/AutoClerk (report generation). Companies sold various BOS accounting software suites in the UK and United States. In the UK, BOS accounting packages were considered to be the industry standard by some accountants. The accounts software was split into four sections: Sales Ledger, Invoices, Purchase Ledger, Daybook and Journal Entries. Data entry and ledger reports were compatible with the Autoclerk report generator software. This feature was especially favoured by accountants and tax officials as it meant that a consultant could sit down with a programmer/operator of the BOS system to plan out and ensure that accounting information was presented in exactly the right way for official acceptance. In the early adoptation of business microcomputers not having accounts correctly laid out was one of the biggest complaints by tax officials. An interesting feature of the command line input was the use of the ESCape key for line entry. This freed up the ENTER key (it was still called RETURN, pre. IBM keyboard layout) to allow the inputting of long lines of code and long spans of data entry. BOS also had its own job control language, simply called BOS/JCL. It made it much easier to delegate otherwise complex operator tasks to non-technical office and shop floor staff, especially given the intricacies of working with multiple floppy disks. BOS applications were initially compiled to a p-code and interpreted as they ran. BOS had a p-code interpreter so efficient that programs, even the BOS/Writer word processor, ran sufficiently fast to satisfy users. A technical subsystem of the system programming software was made available to programmers wanting to write their own p-code microcobol instruction extensions. Apart from a 2-kilobyte (Kb) server (computing)/host kernel, BOS is written in BOS/MicroCobol, a language based on COBOL but with system-level programming constructs added and elements of structured programming, which bore a vague similarity to Pascal. In recent computing, programming languages such as Java have re-introduced the concept of p-code "virtual machines". As the BOS system evolved, the need for programming in ASP.net developed for quicker accessibility and cloud computing. Harrell & Son took the next steps to bring BOS back into the picture on a larger scale. BOS initially required 48 Kb of RAM and two 176 Kb 5.25" double-sided floppies, though it was more commonly deployed on machines equipped with 64 kilobytes of RAM and a hard drive. A computer with 128 KB RAM and a 10-megabyte (Mb) hard drive could run as many as five concurrent users. When the IBM PC XT came out in 1983, BOS served over eight concurrent dumb terminals on it. At the time, this made BOS very attractive. Now, BOS runs on the same required RAM and serves up to 800,000 concurrent users as it is paired with cloud computing. In the early 1980s, a minimal hardware BOS setup might have comprised: North Star Horizon Z80 cpu 48Kbyte ram & 2x 5.25" SA-400 single-density double-sided minifloppy drive (each side used 35/40 tracks to give 176 Kb formatted, ie. BOS used the North Star NSDOS file system), Lynx 24x80 green vdu, DEC LA120 lineprinter/typewriter. Frequent diskette swapping was required during a program run, a good programmer/operator could minimise these essential changes by detailed logical planning. Not every business could quickly afford the newly available hard drives and many company managers were just reluctant to spend more and more upon what they already thought was expensive enough in the first place. Getting an accounts system up and running often involved countless hours poring over thousands of pages of illegible and inaccurate hand-written accounts in traditional ledger books. This is where the journal entry features came in really useful in order to bypass having to enter thousands of useless historical records, it was possible to reach an agreement with the accountants as to what figures should be given an initial fudge factor in order to artificially balance the software ledgers prior to going live with the new accounts system. The software was flexible enough to allow internal adjustments to data. The genius of CAP, or CAP-CPP as it was more correctly called, was to anticipate these technical problems and the initial reservations of a suspicious middle-management, and this was essentially the success of BOS. With user-management tools in the 80's, and application programming interfaces in the mid-80's, BOS was considered an alternative even to the platform-specific operating systems on machines such as the PDP-11 and the VAX. The reemergence of BOS has escalated the number of users requested to be entered into the PMM system, and may require consistent server updating. Despite, or because of its command-line interface, BOS remains popular with medium to large organizations in the UK and US. References STart Magazine: Business Operating System on Atari ST BOS History. Last update January 2020 Proprietary operating systems 1980 software

Operating System (OS)

OS/390 OS/390 is an IBM operating system for the System/390 IBM mainframe computers. Overview OS/390 was introduced in late 1995 in an effort to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional MVS operating system package. These elements included, but were not limited to: Data Facility Storage Management Subsystem Data Facility Product (DFP)Provides access methods to enable I/O to, e.g., DASD subsystems, printers, Tape; provides utilities and program management Job Entry Subsystem (JES)Provides the ability to submit batch work and manage print IBM Communications ServerProvides VTAM and TCP/IP communications protocols An additional benefit of the OS/390 packaging concept was to improve reliability, availability and serviceability (RAS) for the operating system, as the number of different combinations of elements that a customer could order and run was drastically reduced. This reduced the overall time required for customers to test and deploy the operating system in their environments, as well as reducing the number of customer-reported problems (PMRs), errors (APARs) and fixes (PTFs) arising from the variances in element levels. In December 2001 IBM extended OS/390 to include support for 64-bit zSeries processors and added various other improvements, and the result is now named z/OS. IBM ended support for the older OS/390-branded versions in late 2004. See also OS/360 MVS z/OS z/TPF z/VM z/VSE Linux on IBM Z References IBM mainframe operating systems IBM ESA/390 operating systems 1995 software

Operating System (OS)

Distributed operating system A distributed operating system is system software over a collection of independent, networked, communicating, and physically separate computational nodes. They handle jobs which are serviced by multiple CPUs. Each individual node holds a specific software subset of the global aggregate operating system. Each subset is a composite of two distinct service provisioners. The first is a ubiquitous minimal kernel, or microkernel, that directly controls that node's hardware. Second is a higher-level collection of system management components that coordinate the node's individual and collaborative activities. These components abstract microkernel functions and support user applications. The microkernel and the management components collection work together. They support the system's goal of integrating multiple resources and processing functionality into an efficient and stable system. This seamless integration of individual nodes into a global system is referred to as transparency, or single system image; describing the illusion provided to users of the global system's appearance as a single computational entity. Description A distributed OS provides the essential services and functionality required of an OS but adds attributes and particular configurations to allow it to support additional requirements such as increased scale and availability. To a user, a distributed OS works in a manner similar to a single-node, monolithic operating system. That is, although it consists of multiple nodes, it appears to users and applications as a single-node. Separating minimal system-level functionality from additional user-level modular services provides a "separation of mechanism and policy". Mechanism and policy can be simply interpreted as "what something is done" versus "how something is done," respectively. This separation increases flexibility and scalability. Overview The kernel At each locale (typically a node), the kernel provides a minimally complete set of node-level utilities necessary for operating a node's underlying hardware and resources. These mechanisms include allocation, management, and disposition of a node's resources, processes, communication, and input/output management support functions. Within the kernel, the communications sub-system is of foremost importance for a distributed OS. In a distributed OS, the kernel often supports a minimal set of functions, including low-level address space management, thread management, and inter-process communication (IPC). A kernel of this design is referred to as a microkernel. Its modular nature enhances reliability and security, essential features for a distributed OS. System management System management components are software processes that define the node's policies. These components are the part of the OS outside the kernel. These components provide higher-level communication, process and resource management, reliability, performance and security. The components match the functions of a single-entity system, adding the transparency required in a distributed environment. The distributed nature of the OS requires additional services to support a node's responsibilities to the global system. In addition, the system management components accept the "defensive" responsibilities of reliability, availability, and persistence. These responsibilities can conflict with each other. A consistent approach, balanced perspective, and a deep understanding of the overall system can assist in identifying diminishing returns. Separation of policy and mechanism mitigates such conflicts. Working together as an operating system The architecture and design of a distributed operating system must realize both individual node and global system goals. Architecture and design must be approached in a manner consistent with separating policy and mechanism. In doing so, a distributed operating system attempts to provide an efficient and reliable distributed computing framework allowing for an absolute minimal user awareness of the underlying command and control efforts. The multi-level collaboration between a kernel and the system management components, and in turn between the distinct nodes in a distributed operating system is the functional challenge of the distributed operating system. This is the point in the system that must maintain a perfect harmony of purpose, and simultaneously maintain a complete disconnect of intent from implementation. This challenge is the distributed operating system's opportunity to produce the foundation and framework for a reliable, efficient, available, robust, extensible, and scalable system. However, this opportunity comes at a very high cost in complexity. The price of complexity In a distributed operating system, the exceptional degree of inherent complexity could easily render the entire system an anathema to any user. As such, the logical price of realizing a distributed operation system must be calculated in terms of overcoming vast amounts of complexity in many areas, and on many levels. This calculation includes the depth, breadth, and range of design investment and architectural planning required in achieving even the most modest implementation. These design and development considerations are critical and unforgiving. For instance, a deep understanding of a distributed operating system's overall architectural and design detail is required at an exceptionally early point. An exhausting array of design considerations are inherent in the development of a distributed operating system. Each of these design considerations can potentially affect many of the others to a significant degree. This leads to a massive effort in balanced approach, in terms of the individual design considerations, and many of their permutations. As an aid in this effort, most rely on documented experience and research in distributed computing power. History Research and experimentation efforts began in earnest in the 1970s and continued through the 1990s, with focused interest peaking in the late 1980s. A number of distributed operating systems were introduced during this period; however, very few of these implementations achieved even modest commercial success. Fundamental and pioneering implementations of primitive distributed operating system component concepts date to the early 1950s. Some of these individual steps were not focused directly on distributed computing, and at the time, many may not have realized their important impact. These pioneering efforts laid important groundwork, and inspired continued research in areas related to distributed computing. In the mid-1970s, research produced important advances in distributed computing. These breakthroughs provided a solid, stable foundation for efforts that continued through the 1990s. The accelerating proliferation of multi-processor and multi-core processor systems research led to a resurgence of the distributed OS concept. 1950s The DYSEAC One of the first efforts was the DYSEAC, a general-purpose synchronous computer. In one of the earliest publications of the Association for Computing Machinery, in April 1954, a researcher at the National Bureau of Standards now the National Institute of Standards and Technology (NIST) presented a detailed specification of the DYSEAC. The introduction focused upon the requirements of the intended applications, including flexible communications, but also mentioned other computers: The specification discussed the architecture of multi-computer systems, preferring peer-to-peer rather than master-slave. This is one of the earliest examples of a computer with distributed control. The Dept. of the Army reports certified it reliable and that it passed all acceptance tests in April 1954. It was completed and delivered on time, in May 1954. This was a "portable computer", housed in a tractor-trailer, with 2 attendant vehicles and 6 tons of refrigeration capacity. Lincoln TX-2 Described as an experimental input-output system, the Lincoln TX-2 emphasized flexible, simultaneously operational input-output devices, i.e., multiprogramming. The design of the TX-2 was modular, supporting a high degree of modification and expansion. The system employed The Multiple-Sequence Program Technique. This technique allowed multiple program counters to each associate with one of 32 possible sequences of program code. These explicitly prioritized sequences could be interleaved and executed concurrently, affecting not only the computation in process, but also the control flow of sequences and switching of devices as well. Much discussion related to device sequencing. Similar to DYSEAC the TX-2 separately programmed devices can operate simultaneously, increasing throughput. The full power of the central unit was available to any device. The TX-2 was another example of a system exhibiting distributed control, its central unit not having dedicated control. Intercommunicating Cells One early effort at abstracting memory access was Intercommunicating Cells, where a cell was composed of a collection of memory elements. A memory element was basically a binary electronic flip-flop or relay. Within a cell there were two types of elements, symbol and cell. Each cell structure stores data in a string of symbols, consisting of a name and a set of parameters. Information is linked through cell associations. The theory contended that addressing is a wasteful and non-valuable level of indirection. Information was accessed in two ways, direct and cross-retrieval. Direct retrieval accepts a name and returns a parameter set. Cross-retrieval projects through parameter sets and returns a set of names containing the given subset of parameters. This was similar to a modified hash table data structure that allowed multiple values (parameters) for each key (name). This configuration was ideal for distributed systems. The constant-time projection through memory for storing and retrieval was inherently atomic and exclusive. The cellular memory's intrinsic distributed characteristics would be invaluable. The impact on the user, hardware/device, or Application programming interfaces was indirect. The authors were considering distributed systems, stating: Foundational work Coherent memory abstraction Algorithms for scalable synchronization on shared-memory multiprocessors File System abstraction Measurements of a distributed file system Memory coherence in shared virtual memory systems Transaction abstraction Transactions Sagas Transactional Memory Composable memory transactions Transactional memory: architectural support for lock-free data structures Software transactional memory for dynamic-sized data structures Software transactional memory Persistence abstraction OceanStore: an architecture for global-scale persistent storage Coordinator abstraction Weighted voting for replicated data Consensus in the presence of partial synchrony Reliability abstraction Sanity checks The Byzantine Generals Problem Fail-stop processors: an approach to designing fault-tolerant computing systems Recoverability Distributed snapshots: determining global states of distributed systems Optimistic recovery in distributed systems Distributed computing models Three basic distributions To better illustrate this point, examine three system architectures; centralized, decentralized, and distributed. In this examination, consider three structural aspects: organization, connection, and control. Organization describes a system's physical arrangement characteristics. Connection covers the communication pathways among nodes. Control manages the operation of the earlier two considerations. Organization A centralized system has one level of structure, where all constituent elements directly depend upon a single control element. A decentralized system is hierarchical. The bottom level unites subsets of a system's entities. These entity subsets in turn combine at higher levels, ultimately culminating at a central master element. A distributed system is a collection of autonomous elements with no concept of levels. Connection Centralized systems connect constituents directly to a central master entity in a hub and spoke fashion. A decentralized system (aka network system) incorporates direct and indirect paths between constituent elements and the central entity. Typically this is configured as a hierarchy with only one shortest path between any two elements. Finally, the distributed operating system requires no pattern; direct and indirect connections are possible between any two elements. Consider the 1970s phenomena of “string art” or a spirograph drawing as a fully connected system, and the spider's web or the Interstate Highway System between U.S. cities as examples of a partially connected system. Control Centralized and decentralized systems have directed flows of connection to and from the central entity, while distributed systems communicate along arbitrary paths. This is the pivotal notion of the third consideration. Control involves allocating tasks and data to system elements balancing efficiency, responsiveness, and complexity. Centralized and decentralized systems offer more control, potentially easing administration by limiting options. Distributed systems are more difficult to explicitly control, but scale better horizontally and offer fewer points of system-wide failure. The associations conform to the needs imposed by its design but not by organizational chaos Design considerations Transparency Transparency or single-system image refers to the ability of an application to treat the system on which it operates without regard to whether it is distributed and without regard to hardware or other implementation details. Many areas of a system can benefit from transparency, including access, location, performance, naming, and migration. The consideration of transparency directly affects decision making in every aspect of design of a distributed operating system. Transparency can impose certain requirements and/or restrictions on other design considerations. Systems can optionally violate transparency to varying degrees to meet specific application requirements. For example, a distributed operating system may present a hard drive on one computer as "C:" and a drive on another computer as "G:". The user does not require any knowledge of device drivers or the drive's location; both devices work the same way, from the application's perspective. A less transparent interface might require the application to know which computer hosts the drive. Transparency domains: Location transparency – Location transparency comprises two distinct aspects of transparency, naming transparency and user mobility. Naming transparency requires that nothing in the physical or logical references to any system entity should expose any indication of the entity's location, or its local or remote relationship to the user or application. User mobility requires the consistent referencing of system entities, regardless of the system location from which the reference originates. Access transparency – Local and remote system entities must remain indistinguishable when viewed through the user interface. The distributed operating system maintains this perception through the exposure of a single access mechanism for a system entity, regardless of that entity being local or remote to the user. Transparency dictates that any differences in methods of accessing any particular system entity—either local or remote—must be both invisible to, and undetectable by the user. Migration transparency – Resources and activities migrate from one element to another controlled solely by the system and without user/application knowledge or action. Replication transparency – The process or fact that a resource has been duplicated on another element occurs under system control and without user/application knowledge or intervention. Concurrency transparency – Users/applications are unaware of and unaffected by the presence/activities of other users. Failure transparency – The system is responsible for detection and remediation of system failures. No user knowledge/action is involved other than waiting for the system to resolve the problem. Performance Transparency – The system is responsible for the detection and remediation of local or global performance shortfalls. Note that system policies may prefer some users/user classes/tasks over others. No user knowledge or interaction. is involved. Size/Scale transparency – The system is responsible for managing its geographic reach, number of nodes, level of node capability without any required user knowledge or interaction. Revision transparency – The system is responsible for upgrades and revisions and changes to system infrastructure without user knowledge or action. Control transparency – The system is responsible for providing all system information, constants, properties, configuration settings, etc. in a consistent appearance, connotation, and denotation to all users and applications. Data transparency – The system is responsible for providing data to applications without user knowledge or action relating to where the system stores it. Parallelism transparency – The system is responsible for exploiting any ability to parallelize task execution without user knowledge or interaction. Arguably the most difficult aspect of transparency, and described by Tanenbaum as the "Holy grail" for distributed system designers. Inter-process communication Inter-Process Communication (IPC) is the implementation of general communication, process interaction, and dataflow between threads and/or processes both within a node, and between nodes in a distributed OS. The intra-node and inter-node communication requirements drive low-level IPC design, which is the typical approach to implementing communication functions that support transparency. In this sense, Interprocess communication is the greatest underlying concept in the low-level design considerations of a distributed operating system. Process management Process management provides policies and mechanisms for effective and efficient sharing of resources between distributed processes. These policies and mechanisms support operations involving the allocation and de-allocation of processes and ports to processors, as well as mechanisms to run, suspend, migrate, halt, or resume process execution. While these resources and operations can be either local or remote with respect to each other, the distributed OS maintains state and synchronization over all processes in the system. As an example, load balancing is a common process management function. Load balancing monitors node performance and is responsible for shifting activity across nodes when the system is out of balance. One load balancing function is picking a process to move. The kernel may employ several selection mechanisms, including priority-based choice. This mechanism chooses a process based on a policy such as 'newest request'. The system implements the policy Resource management Systems resources such as memory, files, devices, etc. are distributed throughout a system, and at any given moment, any of these nodes may have light to idle workloads. Load sharing and load balancing require many policy-oriented decisions, ranging from finding idle CPUs, when to move, and which to move. Many algorithms exist to aid in these decisions; however, this calls for a second level of decision making policy in choosing the algorithm best suited for the scenario, and the conditions surrounding the scenario. Reliability Distributed OS can provide the necessary resources and services to achieve high levels of reliability, or the ability to prevent and/or recover from errors. Faults are physical or logical defects that can cause errors in the system. For a system to be reliable, it must somehow overcome the adverse effects of faults. The primary methods for dealing with faults include fault avoidance, fault tolerance, and fault detection and recovery. Fault avoidance covers proactive measures taken to minimize the occurrence of faults. These proactive measures can be in the form of transactions, replication and backups. Fault tolerance is the ability of a system to continue operation in the presence of a fault. In the event, the system should detect and recover full functionality. In any event, any actions taken should make every effort to preserve the single system image. Availability Availability is the fraction of time during which the system can respond to requests. Performance Many benchmark metrics quantify performance; throughput, response time, job completions per unit time, system utilization, etc. With respect to a distributed OS, performance most often distills to a balance between process parallelism and IPC. Managing the task granularity of parallelism in a sensible relation to the messages required for support is extremely effective. Also, identifying when it is more beneficial to migrate a process to its data, rather than copy the data, is effective as well. Synchronization Cooperating concurrent processes have an inherent need for synchronization, which ensures that changes happen in a correct and predictable fashion. Three basic situations that define the scope of this need: one or more processes must synchronize at a given point for one or more other processes to continue, one or more processes must wait for an asynchronous condition in order to continue, or a process must establish exclusive access to a shared resource. Improper synchronization can lead to multiple failure modes including loss of atomicity, consistency, isolation and durability, deadlock, livelock and loss of serializability. Flexibility Flexibility in a distributed operating system is enhanced through the modular characteristics of the distributed OS, and by providing a richer set of higher-level services. The completeness and quality of the kernel/microkernel simplifies implementation of such services, and potentially enables service providers greater choice of providers for such services. Research Replicated model extended to a component object model Architectural Design of E1 Distributed Operating System The Cronus distributed operating system Design and development of MINIX distributed operating system Complexity/Trust exposure through accepted responsibility Scale and performance in the Denali isolation kernel. Multi/Many-core focused systems The multikernel: a new OS architecture for scalable multicore systems. Corey: an Operating System for Many Cores. Almos: Advanced Locality Management Operating System for cc-NUMA Many-Cores. Distributed processing over extremes in heterogeneity Helios: heterogeneous multiprocessing with satellite kernels. Effective and stable in multiple levels of complexity Tessellation: Space-Time Partitioning in a Manycore Client OS. See also Distributed computing Plan 9 from Bell Labs Inferno MINIX Single system image (SSI) Computer systems architecture Multikernel List of important publications in concurrent, parallel, and distributed computing Operating System Projects Edsger W. Dijkstra Prize in Distributed Computing List of distributed computing conferences List of distributed computing projects References Further reading External links MIT Parallel and Distributed Operating System Laboratory UCB parallel computing laboratory Parallel Data laboratory The distributed environment of Plan 9 E1 Distributed Operating System Amoeba DOS Source Amoeba home page USENIX: Advanced Computing association How Stuff Works - Operating Systems Algorithms for scalable synchronization Computer networks History of software Operating systems

Operating System (OS)

Network operating system A network operating system (NOS) is a specialized operating system for a network device such as a router, switch or firewall. Historically operating systems with networking capabilities were described as network operating systems, because they allowed personal computers (PCs) to participate in computer networks and shared file and printer access within a local area network (LAN). This description of operating systems is now largely historical, as common operating systems include a network stack to support a client–server model. History Early microcomputer operating systems such as CP/M, MS-DOS and classic Mac OS were designed for one user on one computer. Packet switching networks were developed to share hardware resources, such as a mainframe computer, a printer or a large and expensive hard disk. As local area network technology became available, two general approaches to handle sharing of resources on networks arose. Historically a network operating system was an operating system for a computer which implemented network capabilities. Operating systems with a network stack allowed personal computers to participate in a client-server architecture in which a server enables multiple clients to share resources, such as printers. Early examples of client-server operating systems that were shipped with fully integrated network capabilities are Novell NetWare using the Internetwork Packet Exchange (IPX) network protocol and Banyan VINES which used a variant of the Xerox Network Systems (XNS) protocols. These limited client/server networks were gradually replaced by Peer-to-peer networks, which used networking capabilities to share resources and files located on a variety of computers of all sizes. A peer-to-peer network sets all connected computers equal; they all share the same abilities to use resources available on the network. The most popular peer-to-peer networks as of 2020 are Ethernet, Wi-Fi and the Internet protocol suite. Software that allowed users to interact with these networks, despite a lack of networking support in the underlying manufacturer's operating system, was sometimes called a network operating system. Examples of such add-on software include Phil Karn's KA9Q NOS (adding Internet support to CP/M and MS-DOS), PC/TCP Packet Drivers (adding Ethernet and Internet support to MS-DOS), and LANtastic (for MS-DOS, Microsoft Windows and OS/2), and Windows for Workgroups (adding NetBIOS to Windows). Examples of early operating systems with peer-to-peer networking capabilities built-in include MacOS (using AppleTalk and LocalTalk), and the Berkeley Software Distribution. Today, distributed computing and groupware applications have become the norm. Computer operating systems include a networking stack as a matter of course. During the 1980s the need to integrate dissimilar computers with network capabilities grew and the number of networked devices grew rapidly. Partly because it allowed for multi-vendor interoperability, and could route packets globally rather than being restricted to a single building, the Internet protocol suite became almost universally adopted in network architectures. Thereafter, computer operating systems and the firmware of network devices tended to support Internet protocols. Network device operating systems Network operating systems can be embedded in a router or hardware firewall that operates the functions in the network layer (layer 3). Notable network operating systems include: Proprietary network operating systems Cisco IOS, a family of network operating systems used on most Cisco Systems routers and current Cisco network switches. Earlier switches ran the Catalyst Operating System CatOS RouterOS by MikroTik. ZyNOS, used in network devices made by ZyXEL. LCOS(LX/FX/SX), used in network devices made by LANCOM Systems. NetBSD, FreeBSD, or Linux based operating systems DD-WRT, Linux kernel based DD-WRT is Linux-based firmware for wireless routers and access points as well as low-cost networking device platforms such as the Linksys WRT54G Dell Networking Operating System, DNOS9 is NetBSD based, while OS10 uses the Linux kernel Extensible Operating System runs on switches from Arista and uses an unmodified Linux kernel ExtremeXOS (EXOS), used in network devices made by Extreme Networks FTOS or Force10 Operating System, is the firmware family used on Force10 Ethernet switches OpenWrt used to route IP packets on embedded devices pfSense, a fork of M0n0wall, uses PF OPNsense, a fork of pfSense SONiC, a Linux-based network operating system developed by Microsoft Cumulus Linux distribution, which uses the full TCP/IP stack of Linux VyOS, an open source fork of the Vyatta routing package ONOS, an open source SDN operating system (hosted by The Linux Foundation) for communications service providers that is designed for scalability, high performance and high availability. See also Distributed operating system FRRouting Network Computer Operating System Network functions virtualization Operating System Projects Interruptible operating system SONiC (operating system) References External links Chapter 6 of Dr. Roy Winkelman's guide to networks The open-source NOS for Disaggregated Cell Site Gateways Operating systems Internet Protocol based network software

Operating System (OS)

Raspberry Pi OS Raspberry Pi OS (formerly Raspbian) is a Debian-based operating system for Raspberry Pi. Since 2013, it has been officially provided by the Raspberry Pi Foundation as the primary operating system for the Raspberry Pi family of compact single-board computers. Raspberry Pi OS was first developed by Mike Thompson and Peter Green as Raspbian, an independent and unofficial port of Debian to the Raspberry Pi. The first build was released on July 15, 2012. As the Raspberry Pi had no officially provided operating system at the time, the Raspberry Pi Foundation decided to build off of the work done by the Raspbian project and began producing and releasing their own version of the software. The Foundation's first release of Raspbian, which now referred both to the community project as well as the official operating system, was announced on September 10th, 2013. On May 28th, 2020, the Raspberry Pi Foundation announced they were releasing a beta 64-bit version of their official operating system. However, the 64-bit version was not based on Raspbian, instead taking its userland from Debian directly. Since the Foundation did not want to use the name Raspbian to refer to software that was not based on the Raspbian project, the name of the officially provided operating system was changed to Raspberry Pi OS. This change was carried over to the 32-bit version as well, though it continued to be based on Raspbian. The 64-bit version of Raspberry Pi OS was officially released on February 2nd, 2022. Raspberry Pi OS is highly optimized for the Raspberry Pi line of compact single-board computers with ARM CPUs. It runs on every Raspberry Pi except the Pico microcontroller. Raspberry Pi OS uses a modified LXDE as its desktop environment with the Openbox stacking window manager, along with a unique theme. The default distribution is shipped with a copy of the algebra program Wolfram Mathematica, VLC, and a lightweight version of the Chromium web browser. Features User interface Raspberry Pi OS's desktop environment, PIXEL, looks similar to many common desktops, such as macOS and Microsoft Windows, and is based on LXDE. The menu bar is positioned at the top and contains an application menu and shortcuts to Terminal, Chromium, and File Manager. On the right is a Bluetooth menu, a Wi-Fi menu, volume control, and a digital clock. Package management Packages can be installed via APT, the Recommended Software app, and by using the Add/Remove Software tool, a GUI wrapper for APT. Components PCManFM is a file browser allowing quick access to all areas of the computer, and was redesigned in the first Raspberry Pi OS Buster release (2019-06-20). Raspberry Pi OS originally used Epiphany as the web browser, but switched to Chromium with the launch of its redesigned desktop. Raspberry Pi OS comes with many beginner IDEs, such as Thonny Python IDE, Mu Editor, and Greenfoot. It also ships with educational software like Scratch and Bookshelf. Reception Jesse Smith from DistroWatch reviewed Raspberry Pi OS (then Raspbian) in 2015: Based on download statistics from the Raspberry Pi Imager, Raspberry Pi OS is by far the most used operating system on the Raspberry Pi, accounting for 68.44% of all OS downloads in the past month, as of 24 February 2022. Microsoft repository controversy In late January 2021, the Raspberry Pi OS package added a trusted GPG key and entry to APT. This addition made it easier for users running Raspberry Pi OS to install Visual Studio Code, a source code editor developed by Microsoft. However, this change also meant that every time the system checked for updates, it would query Microsoft's package servers. Given Microsoft's once adversarial history with Linux, this from of telemetry upset some users. The GPG key and APT entry would later be removed. Release history Versions Raspberry Pi OS has three installation versions: Raspberry Pi OS Lite (32-bit & 64-bit) Raspberry Pi OS with desktop (32-bit & 64-bit) Raspberry Pi OS with desktop and recommended software (32-bit) Raspberry Pi OS also has two legacy versions: Raspberry Pi OS Lite (Legacy) (32-bit) Raspberry Pi OS (Legacy) with desktop (32-bit) Raspberry Pi OS Lite is the smallest version and doesn't include a desktop environment. Raspberry Pi OS with desktop includes the Pixel desktop environment. Raspberry Pi OS with desktop and recommended software additionally comes pre-installed with additional productivity software, such as Libre Office. On December 2nd, 2021, the Raspberry Pi Foundation released Raspberry Pi OS (Legacy), a branch of the operating system that continued to receive security and hardware compatibility updates but was based in the older Buster version of Debian. All versions are distributed as .img disk image files. These files can then be flashed on to microSD cards where Raspberry Pi OS runs. In March 2020, the Raspberry Pi Foundation also published the Raspberry Pi Imager, a custom disk flasher that allows for the installation of Raspberry Pi OS as well as other operating systems designed for the Raspberry Pi, including RetroPie, Kodi OS, and others. The Raspberry Pi documentation recommends at least a 4GB microSD card for Raspberry Pi OS Lite, and at least a 8GB microSD card for all other versions. See also Debian References External links Raspberry Pi OS on DistroWatch ARM Linux distributions ARM operating systems Debian-based distributions Operating systems based on the Linux kernel Free software culture and documents Raspberry Pi Linux distributions

Operating System (OS)

DOS/360 and successors Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966. In its time, DOS/360 was the most widely used operating system in the world. DOS versions BOS/360 The Basic Operating System(BOS) was an early version of DOS and TOS which could provide usable functionality on a system with as little as 8 KB of main storage and one 2311 disk drive. TOS/360 TOS/360 (Tape Operating System/360, not a DOS as such and not so called) was an IBM operating system for the System/360, used in the early days around 1965 to support the System/360 Model 30 and similar platforms. TOS, as per the "Tape" in the name, required a tape drive. It shared most of the code base and some manuals with IBM's DOS/360. TOS went through 14 releases, and was discontinued when disks such as the IBM 2311 and IBM 2314 became more affordable at the time of System/360, whereas they had been an expensive luxury on the IBM 7090. DOS/360 DOS/360 was the primary operating system for most small to midsize S/360 installations. DOS/VS DOS/VS was released in 1972. The first DOS/VS release was numbered "Release 28" to signify an incremental upgrade from DOS/360. It added virtual memory in support of the new System/370 series hardware. It used a fixed page table which mapped a single address space of up to 16 megabytes for all partitions combined. DOS/VS increased the number of partitions (separate simultaneous programs) from three (named Background, Foreground 1 and Foreground 2) to five (BG and F1 through F4) and allowed a system wide total of fifteen subtasks. DOS/VS was succeeded by DOS/VSE through z/VSE. DOS/VSE DOS/VSE was introduced in 1979 as an "extended" version of DOS/VS to support the new 4300 processors. The 4300 systems included a feature called ECPS:VSE that provided a single-level storage for both the processor and the I/O channels. DOS/VSE provided support for ECPS:VSE, but could also run on a System/370 without that feature. VSE was the last free version of DOS. VSE/AF VSE/Advanced Functions (VSE/AF) is a product that adds new device support and functionality to DOS/VSE. Many installations installed VSE/AF using products such as VSE System Installation Productivity Option/Extended (VSE System IPO/E), which combines DOS/VSE, VSE/AF and various other products. SSX/VSE SSX/VSE ("Small System Executive") was an attempt by IBM to simplify purchase and installation of VSE by providing a pre-generated system containing the OS and the most popular products. SSX was released in 1982, and later replaced by VSE/SP. SSX was sold by IBM as a bundle of 14 component products (Advanced Functions/VSE, VSE/POWER, ACF/VTAME, VSE/VSAM, CICS/DOS/VS, DOS/VS, Sort/Merge, VSE/ICCF, VSE/OCCF, VSE/IPCS, DOS/COBOL, Back Up/Restore, Space Management, VSE/DITTO), and originally would only agree to offer the individual products separately via RPQ, although IBM later agreed to add those products individually to its price list under pressure from ISVs who claimed that the bundling violated antitrust laws. VSE/SP In 1986 IBM released VSE/SP ("System Product") in conjunction with the announcement of the 9370 processors. VSE/SP replaced SSX/VSE and bundled VSE with the most popular VSE program products such as VSE/AF, ACF/VTAM, CICS, and POWER/VS. VSE/SP supported only 24-bit addresses, despite customer requests to provide an XA (31 bit) version. VSE/ESA VSE/ESA was a 31-bit DOS/VSE version, which was released in 1990 with support for up to 384 MB of real storage. It provided up to twelve static partitions and allowed VSE/POWER and ACF/VTAM to be run in private address spaces. It introduced a new feature called dynamic partitions which could allow up to 150 concurrent jobs, each in its own address space. Version 1 could run in either ESA or 370 mode, with the ESA mode also supporting XA hardware with limitations. Version 2 only supported ESA mode with ESA hardware. z/VSE IBM released z/VSE 3.1 in 2005. This change in naming reflected the new "System z" branding for IBM's mainframe product line, but did not represent a fundamental change in architecture from VSE/ESA 2.7 which preceded it. In particular, it did not support the new 64-bit z/Architecture, running only in 31-bit mode even on 64-bit capable machines. z/VSE 4.1 released in 2007 introduced support for 64-bit real addressing, with up to 8 GB of memory. However, while parts of the supervisor run in 64-bit mode, it only provides 31-bit virtual address spaces to problem state applications. As of 2011 one estimate placed the number of sites using z/VSE at around 4,000. History When developing a new hardware generation of unified System/360 (or S/360) computers, IBM had originally committed to delivering a single operating system, OS/360, also compatible with low-end machines; but hardware was already available and the OS/360 project fell further and further behind schedule, as described at length by Fred Brooks in The Mythical Man-Month. IBM was forced to quickly develop four additional systems: BPS/360 for machines with at least 8 KB of core memory and a punched card reader, BOS/360 for machines with at least 8 KB memory and a disk drive, DOS/360 for machines with at least 16 KB memory and a disk drive, TOS/360 for machines with at least 16 KB memory and a tape drive. When OS/360 was finally released, a year late, it required at least 64 KB of memory. DOS was designed to use little memory, and could run on 16 KB machines, a configuration available on the low-end S/360 model 30. Unlike OS/360, DOS/360 was initially a single-job system which did not support multitasking. A version with multitasking, supporting up to three memory partitions, requiring 32 KB of memory was later released. Despite its limitations, DOS/360 became the most widely used operating system for processors with less than 256 KB of memory because: System/360 hardware sold very well; DOS/360 ran well on System/360 processors which medium-sized organizations could afford; and it was better than the "operating systems" these customers had before. DOS/360 was the operating system which filled the time gap between the announcement of the System/360 and the availability of the intended operating system, OS/360. As a result of the delay, a number of customers implemented DOS systems and committed significant investments to run them. IBM expected that DOS/360 users would soon upgrade to OS/360, but as a result of those investments, they were reluctant to commit to such conversion. IBM then needed to continue to offer DOS/360 as an additional operating system. The Hacker's Jargon File incorrectly states that GECOS (also known as GCOS) was copied from DOS/360, which was not the case, however the Xerox Data Systems Xerox Operating System (XOS) was intentionally similar to DOS to simplify program porting. Hardware requirements DOS/360 required a System/360 CPU (model 25 and above) with the standard instruction set (decimal and floating-point instruction sets optional). The minimum memory requirement was 16 KB; storage protection was required only if multiprogramming was used. A 1052 Model 7 printer-keyboard, either a selector or multiplexor channel, and at least one disk drive was required — initially a 2311 holding 7.25 MB. A card reader, card punch and line printer were usually included, but magnetic tape drives could be substituted. A typical configuration might consist of a S/360 model 30 with 32KB memory and the decimal instruction set, an IBM 2540 card reader/card punch, an IBM 1403 printer, two or three IBM 2311 disks, two IBM 2415 magnetic tape drives, and the 1052-7 console. Technical details The following description applies to DOS/360 except as otherwise noted. Later versions offer additional functionality. Because DOS/360 was designed to run on low-end models of System/360 memory usage was a concern. It was possible to generate a DOS supervisor, the resident portion of the operating system, as small as 5902 bytes. Detailed charts listed memory requirements for each sysgen option, often as little as 100 bytes. A minimum system would leave just over 10 KB of storage available for a single batch partition which was enough to run utilities and all compilers except COBOL, PL/I, and full FORTRAN IV. To keep memory usage as small as possible, DOS was coded entirely in assembly language. Transients The concept of transient area is part of Mythical Man-Month's discussion on design and the use of main memory. To further reduce memory usage, the supervisor employed overlays called transients that were read into one of two reserved transient areas as required. Physical transients were loaded into the 556 byte A-Transient area to handle hardware errors (ERPs), record error-specific data (OBR/MDR) on IJSYSRC, and issue error messages. All A-Transient module names began with $$A. Logical transients were loaded into the 1200 byte B-Transient area to provide common program services like OPEN and CLOSE for LIOCS. All B-Transient module names began with $$B. The use of $$A and $$B prefixes ensured rapid loading of transients because their names were stored first in the directory. DOS/VS added Machine Check and Channel Check Handlers, which were another set of transients all starting with $$RAST and executing in the Recovery Transient area. This was done as part of the reliability, availability, and serviceability (RAS) enhancements for the System/370. Before this addition, machine checks caused termination of the program running and channel checks caused termination of the program accessing the device, at the time of the error. Multiprogramming Like OS/360, initial releases of DOS could run only one program at a time. Later versions of "real" DOS were able to run up to three programs concurrently, in separate memory partitions, supported by the same hardware memory protection features of the more scalable OS/360 operating system. These were identified as BG (background), F1 (foreground 1) and F2 (foreground 2). Multiprogramming was an optional feature of DOS/360, selectable at system generation. A later SYSGEN option allowed batch operation run in either FG partition. Otherwise foreground programs had to be manually started by the computer operator. DOS/VS allowed up to seven concurrent programs, although five or six was a more common number due to the smaller scale of the hardware usually hosting DOS systems. Both DOS and DOS/VS allow the number of partitions to be set at IPL (Initial Program Load), the IBM term for Boot load. Program libraries Executable programs were stored in a Core Image Library. While running, DOS could not reclaim space as programs were deleted or replaced with newer versions. When the Core Image Library became full, it had to be compressed by a utility program, and this could halt development work until it was complete. Many shops simply froze changes for a day, compressed the CIL "off-line", and IPLed with the new Core Image Library at the beginning of a business day. A relocatable library for linkable object programs and a source statement library for assembler macros and include text were also supported. Installations could define additional private relocatable and source statement libraries on other disk volumes. Utilities DOS/360 had a set of utility programs, an Assembler, and compilers for FORTRAN, COBOL and eventually PL/I, and it supported a range of file organizations with access methods to help in using them: Sequential data sets were only read or written, one record block at a time from beginning to end. In indexed (ISAM) files a specified section of each record was defined as a key which could be used to look up specific records. In direct access (BDAM) files, the application program had to specify the physical location on the disk of the data it wanted to access. BDAM programming was not easy and most customers never used it themselves; but it was the fastest way to access data on disks and many software companies used it in their products, especially database management systems such as ADABAS, IDMS and IBM's DBOMP and DL/I. Sequential and ISAM files could store either fixed-length or variable-length records, and all types could occupy more than one disk volume. Telecommunications DOS/360 offered Basic Telecommunications Access Method (BTAM) and Queued Telecommunications Access Method (QTAM). BTAM was primitive and hard to use by later standards, but it allowed communication with almost any type of terminal, which was a big advantage at a time when there was little standardization of communications protocols. The simplicity of its API also allowed the relatively easy interface of external communications processors, which facilitated DOS/360 machines becoming nodes in the multi-tier networks of large organizations. Conversely, QTAM users didn't need as much knowledge about individual devices because QTAM operated at the logical level using the OPEN/CLOSE/GET/PUT macros. Job control All DOS job control statements began with "" in card columns one and two except end-of-job which was "", end-of-data, "", and comments , "". (In the description that follows the character "" represents a single blank.) The statement indicates "the beginning of control information for a job." The format is // JOB <jobname> <comments>. must be one to eight alphanumeric characters to identify the job. are ignored. The statement identifies a program to be executed as a job step. "All control statements necessary for execution must be processed" before the statement is read. The format is // EXEC <program> The statement "can be used to allow for operator action between job steps." The format is // PAUSE <comment>. The comment is used to provide a message to the operator. The statement may be used to display a message to the operator. The format is . The end of data statement marks the end of data in the input stream. The format is /*. Any data on the statement following the blank is ignored. The end of job statement marks the end of a job, and may indicate the end of data to be flushed if the job terminates abnormally. The format is /&. Any data on the statement following the blank is ignored. The statement specifies values of system options that apply to this job. The format is // OPTION <option1>[,<option2>...]. The statement "is used to assign a logical I/O unit to a physical device." The format is // ASSGN SYSxxx,<device>[,<tape option>]. SYSxxx indicates a logical unit such as SYS001 or SYSIPT. is either "X'cuu'" to indicate a physical device (channel and unit), "IGN" for ignore, or "UA" for unassigned. specifies either tape mode settings such as density, parity, etc., or "ALT" to indicate an alternate device. The statement resets specified I/O unit assignments to their permanent values. The format is // RESET <option>. may be "SYS" to reset all system logical unit assignments, "PROG" to reset all programmer assignments, "ALL" to reset all assignments, or "SYSxxx" to reset the assignment for the logical unit "SYSxxx", for example SYS002. The statement instructs the system to print a listing of all specified I/O assignments currently in effect. The format is // LISTIO <option>. is "SYS" to list all system assignments, "PROG", "F1", or "F2" to list all assignments for the background or specified foreground partition, "ALL", "SYSxxx", "X'cuu'", "UNITS" to list all assigned units, 'UA" to list all unassigned units, or "DOWN" to list all units marked as inoperative. The statement issues command to a magnetic tape unit. The format is // MTC <opcode>,SYSxxx[,<nn>]. is a function such as "FSF" to forward space one file or "REW" to rewind the tape. is a number that can specify the number of times the operation is to be performed, such as forward space two files. The statement provides disk or tape volume label information for standard label checking. The format is // VOL SYSxxx,<volume>. DOS originally provided the statement for tape label information and the and statements for disk label and extent information. At least as early as 1968 the statement had been replaced by and the statement by . These statements used numerous positional parameters and had fairly high information densities. Differences from OS/360 Job control language DOS JCL was designed for parsing speed and simplicity; the resulting positional syntax was significantly more cryptic than OS/360 keyword-driven job control. Spooling Early DOS included no spooling sub-system to improve the efficiency of punched card and line printer I/O. By the late 1960s both IBM and aftermarket vendors began filling this void. IBM's spooler was an option called POWER, and Software Design, Inc., an independent software company, sold a spooler called GRASP. Program loading DOS/360 had no relocating loader, so programmers had to link edit a separate executable version of each program for each partition, or address space, in which the program was likely to be run. Alternatively assembler-language programs could be written as self-relocating, but that imposed additional complexity and a size penalty, albeit a small one. Large DOS shops with multiple machines and multiple partition layouts often wrote their own relocating loader to circumvent this issue. Application programming interface The DOS/360 application programming interface was incompatible with OS/360. High level language programs written for DOS needed to be compiled and linked before they could be used with OS/360. Minor differences between compilers of DOS as opposed to OS sometimes required modifications to programs. The port in the other direction however was more challenging. Since OS/360 had significantly more features supported in its API, any use of those features would have to be removed from programs being ported to DOS. This was less of a problem for programmers working in high level languages such as COBOL. Assembler programs, on the other hand, tended to utilize those very features more often and usually needed greater modification to run on DOS. See also Timeline of operating systems Notes References External links DOS manuals at Bitsavers.org DOS/VS section at VintageBigBlue.org Disk operating systems IBM mainframe operating systems Assembly language software

Operating System (OS)

Data General AOS Data General AOS (an abbreviation for Advanced Operating System) was the name of a family of operating systems for Data General 16-bit Eclipse C, M, and S minicomputers, followed by AOS/VS and AOS/RT32 (1980) and later AOS/VS II (1988) for the 32-bit Eclipse MV line. Overview AOS/VS exploited the 8-ring protection architecture of the Eclipse MV hardware with ring 7 being the least privileged and ring 0 being the most privileged. The AOS/VS kernel ran in ring 0 and used ring-1 addresses for data structures related to virtual address translations. Ring 2 was unused and reserved for future use by the kernel. The Agent, which performed much of the system call validation for the AOS/VS kernel, as well as some I/O buffering and many compatibility functions, ran in ring 3 of each process. Ring 4 was used by various D.G. products such as the INFOS II DBMS. Rings 5 and 6 were reserved for use by user programs but rarely used except for large software such as the MV/UX inner-ring emulator and Oracle which used ring 5. All user programs ran in ring 7. The AOS software was far more advanced than competing PDP-11 operating systems. 16-bit AOS applications ran natively under AOS/VS and AOS/VS II on the 32-bit Eclipse MV line. AOS/VS (Advanced Operating System/Virtual Storage) was the most commonly used DG software product, and included a command-line interpreter (CLI) allowing for complex scripting, DUMP/LOAD, and other custom components. The 16-bit version of the CLI is famous for including an Easter egg meant to honor Xyzzy (which was pronounced "magic"). This was the internal code name of what externally became known as the AOS/VS 32-bit operating system. A user typing in the command "xyzzy" would get back a response from the CLI of "Nothing Happens". When a 32-bit version of the CLI became available under AOS/VS II, the same command instead reported "Twice As Much Happens". A modified version of System V.2 Unix called MV/UX hosted under AOS/VS was also available. A modified version of System V Unix called DG/UX was made for the Eclipse MV line and later the 88K and x86 AViiON machines. The AOS and AOS/VS kernels were written entirely in assembly language. Almost all of the AOS and AOS/VS utilities included in the operating system releases were written in DG/L a variant of the ALGOL/60 programming language. Initially, AOS/VS utilities closely tracked AOS source development. As AOS/VS matured, many DG-supplied utilities were rewritten to take advantage of the 32-bit address space and reduce dependencies on assembly language, often resulting in substantial increases in functionality, performance and reliability compared with their AOS ancestors. Session **** Atari S/W Development HCD1 / BATCH OUTPUT FILE **** AOS/VS 3.07 / EXEC 3.07 19-JAN-84 10:11:01 QPRI=254 SEQ=31324 INPUT FILE -- :UDD:SYSTEMS:850:?031.CLI.004.JOB (WILL BE DELETED AFTER PROCESSING) LIST FILE -- :QUEUE:NORDIN.LIST.31324 -------- LAST MESSAGE CHANGE 12-JAN-84 16:06:08 Atari S/W Development System HCD1 Backup schedule (system shut down): Saturday 21-Jan-84 9:30-11:30am Refer to HELP *COMMANDS, HELP *PSEUDO, HELP, APHELP, and ?MHELP. Refer to DISP FUNC in SED for list of default function key commands. -------- LAST PREVIOUS LOGON 19-JAN-84 10:09:45 * searchlist :UDD:NORDIN:UTIL :UDD:NORDIN:LINKS :C :UTIL : AOS/VS CLI REV 03.03.00.00 19-JAN-84 10:11:05 Ý SEARCHLIST :UDD:SYSTEMS:UTIL,:UDD:NORDIN:UTIL,:UDD:NORDIN:LINKS,:C,:UTIL,: Ý DIRECTORY :UDD:SYSTEMS:850 Ý DEFACL SYSTEMS,OWARE,A.JOE,OWARE,A.OLIVIA,OWARE,ARKEN,OWARE,BLOTCKY,OWARE,NORDIN,OWARE,TITTSLER,OWARE,FOWKES,OWARE Ý CAMAC R850AMAC H=R850AMAC.OBJ L=R850AMAC.PRN R=F SL=132 ATARI CAMAC Assembler Ver 1.0A Copyright 1981 ATARI Inc. Enter source file name and options d:R850AMAC h=d:R850AMAC.OBJ l=d:R850AMAC.PRN R=F SL=132 Pass 1 - Reading D1:R850AMAC. Pass 2 - Reading D1:R850AMAC. no ERRORs, 669 Labels, $67E8 free. � ATARI CAMAC Assembler Ver 1.0A Copyright 1981 ATARI Inc. Enter source file name and options Ý Ý END OF FILE AOS/VS CLI TERMINATING 19-JAN-84 10:12:06 PROCESS 42 TERMINATED ELAPSED TIME 0:01:06 (OTHER JOBS, SAME USERNAME) USER 'NORDIN' LOGGED OFF 19-JAN-84 10:12:07 **** * LIST FILE EMPTY, WILL NOT BE PRINTED **** See also Data General RDOS CEO (Data General) References Proprietary operating systems Data General

Operating System (OS)

OS/7 OS/7 is a discontinued operating system from Sperry Univac for its 90/60 and 90/70 computer systems. The system was first announced in November 1971 for Univac's 9700 system and was originally scheduled for delivery in March 1973. However, the delivery slipped by nearly a year, which impacted the 9700 marketing effort. It was first demonstrated by Univac on the new 90/60 system in October 1973. The official release was then planned for January 1974. OS/7 was abruptly discontinued in 1975 in favor of VS/9, Univac's name for RCA's VMOS operating system. "OS/7 is a multi-tasking, multi-programming system that utilizes a roll-in, roll-out capability to keep the CPU optimally busy." References Discontinued operating systems UNIVAC mainframe computers

Operating System (OS)

DOS DOS (, ) is a platform-independent acronym for disk operating system which later became a common shorthand for disk-based operating systems on IBM PC compatibles. DOS primarily consists of Microsoft's MS-DOS and a rebranded version under the name IBM PC DOS, both of which were introduced in 1981. Later compatible systems from other manufacturers include DR DOS (1988), ROM-DOS (1989), PTS-DOS (1993), and FreeDOS (1998). MS-DOS dominated the IBM PC compatible market between 1981 and 1995. Dozens of other operating systems also use the acronym "DOS", beginning with the mainframe DOS/360 from 1966. Others include Apple DOS, Apple ProDOS, Atari DOS, Commodore DOS, TRSDOS, and AmigaDOS. History Origins IBM PC DOS (and the separately sold MS-DOS) and its predecessor, 86-DOS, was based on Digital Research's CP/M—the dominant disk operating system for 8-bit Intel 8080 and Zilog Z80 microcomputers—but instead ran on Intel 8086 16-bit processors. When IBM introduced the IBM PC, built with the Intel 8088 microprocessor, they needed an operating system. Seeking an 8088-compatible build of CP/M, IBM initially approached Microsoft CEO Bill Gates (possibly believing that Microsoft owned CP/M due to the Microsoft Z-80 SoftCard, which allowed CP/M to run on an Apple II). IBM was sent to Digital Research, and a meeting was set up. However, the initial negotiations for the use of CP/M broke down; Digital Research wished to sell CP/M on a royalty basis, while IBM sought a single license, and to change the name to "PC DOS". Digital Research founder Gary Kildall refused, and IBM withdrew. IBM again approached Bill Gates. Gates in turn approached Seattle Computer Products. There, programmer Tim Paterson had developed a variant of CP/M-80, intended as an internal product for testing SCP's new 16-bit Intel 8086 CPU card for the S-100 bus. The system was initially named QDOS (Quick and Dirty Operating System), before being made commercially available as 86-DOS. Microsoft purchased 86-DOS, allegedly for . This became Microsoft Disk Operating System, MS-DOS, introduced in 1981. Within a year Microsoft licensed MS-DOS to over 70 other companies, which supplied the operating system for their own hardware, sometimes under their own names. Microsoft later required the use of the MS-DOS name, with the exception of the IBM variant. IBM continued to develop their version, PC DOS, for the IBM PC. Digital Research became aware that an operating system similar to CP/M was being sold by IBM (under the same name that IBM insisted upon for CP/M), and threatened legal action. IBM responded by offering an agreement: they would give PC consumers a choice of PC DOS or CP/M-86, Kildall's 8086 version. Side-by-side, CP/M cost more than PC DOS, and sales were low. CP/M faded, with MS-DOS and PC DOS becoming the marketed operating system for PCs and PC compatibles. Microsoft originally sold MS-DOS only to original equipment manufacturers (OEMs). One major reason for this was that not all early PCs were 100% IBM PC compatible. DOS was structured such that there was a separation between the system specific device driver code (IO.SYS) and the DOS kernel (MSDOS.SYS). Microsoft provided an OEM Adaptation Kit (OAK) which allowed OEMs to customize the device driver code to their particular system. By the early 1990s, most PCs adhered to IBM PC standards so Microsoft began selling MS-DOS in retail with MS-DOS 5.0. In the mid-1980s Microsoft developed a multitasking version of DOS. This version of DOS is generally referred to as "European MS-DOS 4" because it was developed for ICL and licensed to several European companies. This version of DOS supports preemptive multitasking, shared memory, device helper services and New Executable ("NE") format executables. None of these features were used in later versions of DOS, but they were used to form the basis of the OS/2 1.0 kernel. This version of DOS is distinct from the widely released PC DOS 4.0 which was developed by IBM and based upon DOS 3.3. Digital Research attempted to regain the market lost from CP/M-86, initially with Concurrent DOS, FlexOS and DOS Plus (both compatible with both MS-DOS and CP/M-86 software), later with Multiuser DOS (compatible with both MS-DOS and CP/M-86 software) and DR DOS (compatible with MS-DOS software). Digital Research was bought by Novell, and DR DOS became PalmDOS and Novell DOS; later, it was part of Caldera (under the names OpenDOS and DR-DOS 7.02/7.03), Lineo, and DeviceLogics. Gordon Letwin wrote in 1995 that "DOS was, when we first wrote it, a one-time throw-away product intended to keep IBM happy so that they'd buy our languages". Microsoft expected that it would be an interim solution before Xenix. The company planned to over time improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the Motorola 68000, Zilog Z-8000, and LSI-11; they would be upwardly compatible with Xenix, which BYTE in 1983 described as "the multi-user MS-DOS of the future". IBM, however, did not want to replace DOS. After AT&T began selling Unix, Microsoft and IBM began developing OS/2 as an alternative. The two companies later had a series of disagreements over two successor operating systems to DOS, OS/2 and Windows. They split development of their DOS systems as a result. The last retail version of MS-DOS was MS-DOS 6.22; after this, MS-DOS became part of Windows 95, 98 and Me. The last retail version of PC DOS was PC DOS 2000 (also called PC DOS 7 revision 1), though IBM did later develop PC DOS 7.10 for OEMs and internal use. The FreeDOS project began in 26 June 1994, when Microsoft announced it would no longer sell or support MS-DOS. Jim Hall then posted a manifesto proposing the development of an open-source replacement. Within a few weeks, other programmers including Pat Villani and Tim Norman joined the project. A kernel, the COMMAND.COM command line interpreter (shell), and core utilities were created by pooling code they had written or found available. There were several official pre-release distributions of FreeDOS before the FreeDOS 1.0 distribution was released on 3 September 2006. Made available under the GNU General Public License (GPL), FreeDOS does not require license fees or royalties. Decline Early versions of Microsoft Windows ran on a separate version of MS-DOS. By the early 1990s, the Windows graphical shell saw heavy use on new DOS systems. In 1995, Windows 95 was bundled as a standalone operating system that did not require a separate DOS license. Windows 95 (and Windows 98 and ME, that followed it) took over as the default OS kernel, though the MS-DOS component remained for compatibility. With Windows 95 and 98, but not ME, the MS-DOS component could be run without starting Windows. With DOS no longer required to use Windows, the majority of users stopped using it directly. Continued use Available compatible systems in 2012 are FreeDOS, DR-DOS, ROM-DOS, PTS-DOS, RxDOS and REAL/32. Some computer manufacturers, including Dell and HP, sell computers with FreeDOS and DR-DOS as OEM operating systems. Embedded systems DOS's structure of accessing hardware directly allows it to be used in embedded devices. The final versions of DR-DOS are still aimed at this market. ROM-DOS is used as operating system for the Canon PowerShot Pro 70. Emulation On Linux, it is possible to run DOSEMU, a Linux-native virtual machine for running DOS programs at near native speed. There are a number of other emulators for running DOS on various versions of Unix and Microsoft Windows such as DOSBox. DOSBox is designed for legacy gaming (e.g. King's Quest, Doom) on modern operating systems. Design MS-DOS and IBM PC DOS related operating systems are commonly associated with machines using the Intel x86 or compatible CPUs, mainly IBM PC compatibles. Machine-dependent versions of MS-DOS were produced for many non-IBM-compatible x86-based machines, with variations from relabelling of the Microsoft distribution under the manufacturer's name, to versions specifically designed to work with non-IBM-PC-compatible hardware. As long as application programs used DOS APIs instead of direct hardware access, they could run on both IBM-PC-compatible and incompatible machines. The original FreeDOS kernel, DOS-C, was derived from DOS/NT for the Motorola 68000 series of CPUs in the early 1990s. While these systems loosely resembled the DOS architecture, applications were not binary compatible due to the incompatible instruction sets of these non-x86-CPUs. However, applications written in high-level languages could be ported easily. DOS is a single-user, single-tasking operating system with basic kernel functions that are non-reentrant: only one program at a time can use them, and DOS itself has no functionality to allow more than one program to execute at a time. The DOS kernel provides various functions for programs (an application program interface), like character I/O, file management, memory management, program loading and termination. DOS provides the ability for shell scripting via batch files (with the filename extension .BAT). Each line of a batch file is interpreted as a program to run. Batch files can also make use of internal commands, such as GOTO and conditional statements. The operating system offers an application programming interface that allows development of character-based applications, but not for accessing most of the hardware, such as graphics cards, printers, or mice. This required programmers to access the hardware directly, usually resulting in each application having its own set of device drivers for each hardware peripheral. Hardware manufacturers would release specifications to ensure device drivers for popular applications were available. Boot sequence The bootstrap loader on PC-compatible computers, the master boot record, is located beginning at the boot sector, the first sector on the first track (track zero), of the boot disk. The ROM BIOS will load this sector into memory at address :, and typically check for a signature "" at offset . If the sector is not considered to be valid, the ROM BIOS will try the next physical disk in the row, otherwise it will jump to the load address with certain registers set up. If the loaded boot sector happens to be a Master Boot Record (MBR), as found on partitioned media, it will relocate itself to : in memory, otherwise this step is skipped. The MBR code will scan the partition table, which is located within this sector, for an active partition (modern MBRs check if bit 7 is set at offset , whereas old MBRs simply check for a value of ), and, if found, load the first sector of the corresponding partition, which holds the Volume Boot Record (VBR) of that volume, into memory at : in the similar fashion as if it had been loaded by the ROM BIOS itself. The MBR will then pass execution to the loaded portion with certain registers set up. The sector content loaded at : constitutes a VBR now. VBRs are operating system specific and cannot be exchanged between different DOS versions in general, as the exact behaviour differs between different DOS versions. In very old versions of DOS such as DOS 1.x, the VBR would load the whole IO.SYS/IBMBIO.COM file into memory at :. For this to work, these sectors had to be stored in consecutive order on disk by SYS. In later issues, it would locate and store the contents of the first two entries in the root directory at : and if they happen to reflect the correct boot files as recorded in the VBR, the VBR would load the first 3 consecutive sectors of the IO.SYS/IBMBIO.COM file into memory at :. The VBR also has to take care to preserve the contents of the Disk Parameter Table (DPT). Finally, it passes control to the loaded portion by jumping to its entry point with certain registers set up (with considerable differences between different DOS versions). In later DOS versions, where the VBR has loaded only the first 3 sectors of the IO.SYS/IBMBIO.COM file into memory, the loaded portion contains another boot loader, which will then load the remainder of itself into memory, using the root directory information stored at :. For most versions, the file contents still need to be stored in consecutive order on disk. In older versions of DOS, which were still loaded as a whole, this step is skipped. The DOS system initialization code will initialize its built-in device drivers and then load the DOS kernel, located in MSDOS.SYS on MS-DOS systems, into memory as well. In Windows 9x, the DOS system initialization code and built-in device drivers and the DOS kernel are combined into a single IO.SYS file while MSDOS.SYS is used as a text configuration file. The CONFIG.SYS file is then read to parse configuration parameters. The variable specifies the location of the shell which defaults to COMMAND.COM. The shell is loaded and executed. The startup batch file AUTOEXEC.BAT is then run by the shell. The DOS system files loaded by the boot sector must be contiguous and be the first two directory entries. As such, removing and adding this file is likely to render the media unbootable. It is, however, possible to replace the shell at will, a method that can be used to start the execution of dedicated applications faster. This limitation does not apply to any version of DR DOS, where the system files can be located anywhere in the root directory and do not need to be contiguous. Therefore, system files can be simply copied to a disk provided that the boot sector is DR DOS compatible already. In PC DOS and DR DOS 5.0 and above, the DOS system files are named IBMBIO.COM instead of IO.SYS and IBMDOS.COM instead of MSDOS.SYS. Older versions of DR DOS used DRBIOS.SYS and DRBDOS.SYS instead. Starting with MS-DOS 7.0 the binary system files IO.SYS and MSDOS.SYS were combined into a single file IO.SYS whilst MSDOS.SYS became a configuration file similar to CONFIG.SYS and AUTOEXEC.BAT. If the MSDOS.SYS BootGUI directive is set to 0, the boot process will stop with the command processor (typically COMMAND.COM) loaded, instead of executing WIN.COM automatically. File system DOS uses a filesystem which supports 8.3 filenames: 8 characters for the filename and 3 characters for the extension. Starting with DOS 2 hierarchical directories are supported. Each directory name is also 8.3 format but the maximum directory path length is 64 characters due to the internal current directory structure (CDS) tables that DOS maintains. Including the drive name, the maximum length of a fully qualified filename that DOS supports is 80 characters using the format drive:\path\filename.ext followed by a null byte. DOS uses the File Allocation Table (FAT) filesystem. This was originally FAT12 which supported up to 4078 clusters per drive. DOS 3.0 added support for FAT16 which used 16-bit allocation entries and supported up to 65518 clusters per drive. Compaq MS-DOS 3.31 added support for FAT16B which removed the 32#8209;MB drive limit and could support up to 512 MB. Finally MS-DOS 7.1 (the DOS component of Windows 9x) added support for FAT32 which used 32-bit allocation entries and could support hard drives up to 137 GB and beyond. Starting with DOS 3.1, file redirector support was added to DOS. This was initially used to support networking but was later used to support CD-ROM drives with MSCDEX. IBM PC DOS 4.0 also had preliminary installable file system (IFS) support but this was unused and removed in DOS 5.0. DOS also supported Block Devices ("Disk Drive" devices) loaded from CONFIG.SYS that could be used under the DOS file system to support network devices. Drive naming scheme In DOS, drives are referred to by identifying letters. Standard practice is to reserve "A" and "B" for floppy drives. On systems with only one floppy drive DOS assigns both letters to the drive, prompting the user to swap disks as programs alternate access between them. This facilitates copying from floppy to floppy or having a program run from one floppy while accessing its data on another. Hard drives were originally assigned the letters "C" and "D". DOS could only support one active partition per drive. As support for more hard drives became available, this developed into first assigning a drive letter to each drive's active primary partition, then making a second pass over the drives to allocate letters to logical drives in the extended partition, then a third pass to give any other non-active primary partitions their names (where such additional partitions existed and contained a DOS-supported file system). Lastly, DOS allocates letters for optical disc drives, RAM disks, and other hardware. Letter assignments usually occur in the order the drivers are loaded, but the drivers can instruct DOS to assign a different letter; drivers for network drives, for example, typically assign letters nearer the end of the alphabet. Because DOS applications use these drive letters directly (unlike the /dev directory in Unix-like systems), they can be disrupted by adding new hardware that needs a drive letter. An example is the addition of a new hard drive having a primary partition where a pre-existing hard drive contains logical drives in extended partitions; the new drive will be assigned a letter that was previously assigned to one of the extended partition logical drives. Moreover, even adding a new hard drive having only logical drives in an extended partition would still disrupt the letters of RAM disks and optical drives. This problem persisted through Microsoft's DOS-based 9x versions of Windows until they were replaced by versions based on the NT line, which preserves the letters of existing drives until the user changes them. Under DOS, this problem can be worked around by defining a SUBST drive and installing the DOS program into this logical drive. The assignment of this drive would then be changed in a batch job whenever the application starts. Under some versions of Concurrent DOS, as well as under Multiuser DOS, System Manager and REAL/32, the reserved drive letter L: will automatically be assigned to the corresponding load drive whenever an application starts. Reserved device names There are reserved device names in DOS that cannot be used as filenames regardless of extension as they are occupied by built-in character devices. These restrictions also affect several Windows versions, in some cases causing crashes and security vulnerabilities. The reserved names are: CON, for console AUX, for auxiliary PRN, for printer LST, for lister; introduced with 86-DOS 0.74. NUL, for null devices; added in 86-DOS 1.10 and PC DOS 1.0. These names (except for NUL) have continued to be supported in all versions of MS-DOS, PC DOS and DR-DOS ever since. LST was also available in some OEM versions of MS-DOS 1.25, whereas other OEM versions of MS-DOS 1.25 already used LPT1 (first line printer) and COM1 (first serial communication device) instead, as introduced with PC DOS. In addition to LPT1 and LPT2 as well as COM1 to COM3, Hewlett-Packard's MS-DOS 2.11 for the HP Portable Plus also supported LST as alias for LPT2 and 82164A as alias for COM2; it also supported PLT for plotters. Otherwise, COM2, LPT2, LPT3 and the CLOCK$ (still named CLOCK in some issues of MS-DOS 2.11) clock device were introduced with DOS 2.0, and COM3 and COM4 were added with DOS 3.3. Only the multitasking MS-DOS 4 supported KEYBD$ and SCREEN$. DR DOS 5.0 and higher and Multiuser DOS support an $IDLE$ device for dynamic idle detection to saving power and improve multitasking. LPT4 is an optional built-in driver for a fourth line printer supported in some versions of DR-DOS since 7.02. CONFIG$ constitutes the real mode PnP manager in MS-DOS 7.0–8.0. AUX typically defaults to COM1, and PRN to LPT1 (LST), but these defaults can be changed in some versions of DOS to point to other serial or parallel devices. PLT was reconfigurable as well. Filenames ended with a colon () such as NUL: conventionally indicate device names, but the colon is not actually a part of the name of the built-in device drivers. Colons are not necessary to be typed in some cases, for example: ECHO This achieves nothing > NUL It is still possible to create files or directories using these reserved device names, such as through direct editing of directory data structures in disk sectors. Such naming, such as starting a file name with a space, has sometimes been used by viruses or hacking programs to obscure files from users who do not know how to access these locations. Memory management DOS was designed for the Intel 8088 processor which can only directly access a maximum of 1 MB of RAM. Both IBM and Microsoft chose 640 KB as the maximum amount of memory available to programs and reserved the remaining 384 KB for video memory, the read-only memory of adapters on some video and network peripherals, and the system's BIOS. Microsoft believed that the 640 KB barrier would never be reached. However, by 1985, some DOS applications were already hitting the memory limit, while much of reserved was unused, depending on the machine's specifications. Specifications were developed to allow access to additional memory. The first was the Expanded Memory Specification (EMS) was designed to allow memory on an add-on card to be accessed via a 64 KB page frame in the reserved upper memory area. 80386 and later systems could use a virtual 8086 mode (V86) mode memory manager like EMM386 to create expanded memory from extended memory without the need of an add-on card. The second specification was the Extended Memory Specification (XMS) for 80286 and later systems. This provided a way to copy data to and from extended memory, access to the 65,520-byte high memory area directly above the first megabyte of memory and the upper memory block area. Generally XMS support was provided by HIMEM.SYS or a V86 mode memory manager like QEMM or 386MAX which also supported EMS. Starting with DOS 5, DOS could directly take advantage of the HMA by loading its kernel code and disk buffers there via the DOS=HIGH statement in CONFIG.SYS. DOS 5+ also allowed the use of available upper memory blocks via the DOS=UMB statement in CONFIG.SYS. DOS under OS/2 and Windows The DOS emulation in OS/2 and Windows runs in much the same way as native applications do. They can access all of the drives and services, and can even use the host's clipboard services. Because the drivers for file systems and such forth reside in the host system, the DOS emulation needs only provide a DOS API translation layer which converts DOS calls to OS/2 or Windows system calls. The translation layer generally also converts BIOS calls and virtualizes common I/O port accesses which many DOS programs commonly use. In Windows 3.1 and 9x, the DOS virtual machine is provided by WINOLDAP. WinOldAp creates a virtual machine based on the program's PIF file, and the system state when Windows was loaded. The DOS graphics mode, both character and graphic, can be captured and run in the window. DOS applications can use the Windows clipboard by accessing extra published calls in WinOldAp, and one can paste text through the WinOldAp graphics. The emulated DOS in OS/2 and Windows NT is based upon DOS 5. Although there is a default configuration (config.sys and autoexec.bat), one can use alternate files on a session-by-session basis. It is possible to load drivers in these files to access the host system, although these are typically third-party. Under OS/2 2.x and later, the DOS emulation is provided by DOSKRNL. This is a file that represents the combined IBMBIO.COM and IBMDOS.COM, the system calls are passed through to the OS/2 windowing services. DOS programs run in their own environment, the bulk of the DOS utilities are provided by bound DOS / OS2 applications in the \OS2 directory. OS/2 can run Windows 3.1 applications by using a modified copy of Windows (Win-OS/2). The modifications allow Windows 3.1 programs to run seamlessly on the OS/2 desktop, or one can start a WinOS/2 desktop, similar to starting Windows from DOS. OS/2 allows for 'DOS from Drive A:', (VMDISK). This is a real DOS, like MS-DOS 6.22 or PC DOS 5.00. One makes a bootable floppy disk of the DOS, adds a number of drivers from OS/2, and then creates a special image. The DOS booted this way has full access to the system, but provides its own drivers for hardware. One can use such a disk to access cdrom drives for which there is no OS/2 driver. In all 32-bit (IA-32) editions of the Windows NT family since 1993, DOS emulation is provided by way of a virtual DOS machine (NTVDM). 64-bit (IA-64) versions of Windows do not support NTVDM and cannot run 16-bit DOS applications directly; third-party emulators such as DOSbox can be used to run DOS programs on those machines. User interface DOS systems use a command-line interface. A program is started by entering its filename at the command prompt. DOS systems include utility programs and provide internal commands that don't correspond to programs. In an attempt to provide a more user-friendly environment, numerous software manufacturers wrote file management programs that provided users with menu- and/or icon-based interfaces. becoming a self-contained program loader, and replacing DOS as the most-used PC-compatible program loader. Text user interface programs included Norton Commander, DOS Navigator, Volkov Commander, Quarterdesk DESQview, and Sidekick. Graphical user interface programs included Digital Research's GEM (originally written for CP/M) and GEOS. Eventually, the manufacturers of major DOS systems began to include their own environment managers. MS-DOS/IBM DOS 4 included DOS Shell; DR DOS 5.0, released the following year, included ViewMAX, based upon GEM. Terminate and Stay Resident DOS is not a multitasking operating system. DOS did however provide a Terminate and Stay Resident (TSR) function which allowed programs to remain resident in memory. These programs could hook the system timer and/or keyboard interrupts to allow themselves to run tasks in the background or to be invoked at any time preempting the current running program effectively implementing a simple form of multitasking on a program-specific basis. The PRINT command did this to implement background print spooling. Borland Sidekick, a popup personal information manager (PIM), also used this technique. Terminate and Stay Resident programs were also used to provide additional features not available by default. Programs like CED and DOSKEY provided command line editing facilities beyond what was available in COMMAND.COM. Programs like the Microsoft CD-ROM Extensions (MSCDEX) provided access to files on CD-ROM disks. Some TSRs could even perform a rudimentary form of task switching. For example, the shareware program Back and Forth (1990) had a hotkey to save the state of the currently-running program to disk, load another program, and switch to it, hence it was possible to switch "back and forth" between programs, albeit slowly due to the disk access required. Back and Forth could not enable background processing however; that needed DESQview (on at least a 386). Software Arachne, a 16-bit graphical web browser dBase, database program Harvard Graphics, a presentation graphics design program Lotus 1-2-3, a spreadsheet has been credited with the success of the IBM PC Norton Commander and XTree, file management utilities PKZIP, the compression utility that quickly became the standard in file compression ProComm, Qmodem, and Telix, modem communication programs Sidekick, personal information manager that could be used from within other programs WordPerfect, a word processor that was dominant in the 1980s WordStar, word processor originally for CP/M that became popular on the IBM PC Development tools BASIC language interpreters. BASICA and GW-BASIC DJGPP, the 32-bit DPMI DOS port of gcc Microsoft Macro Assembler, Microsoft C, and CodeView from Microsoft Watcom C/C++ from Watcom Turbo Pascal, Turbo BASIC, Turbo C, Turbo Prolog, and Turbo Assembler from Borland See also COMMAND.COM (the command line interpreter for DOS and Windows 9x) CP/M (Digital Research early operating system similar to DOS) (DCP, an MS-DOS derivative by the former East-German VEB Robotron) DOS API DOS/V Index of DOS games List of DOS operating systems PC-MOS/386 (a DOS-compatible multiuser operating system) VGA-compatible text mode, the base of DOS's TUI on IBM PC compatibles References Further reading IBM Corp., IBM, (January 1984). "IBM DOS Release 2.10 Cloth bound retail hard board box". 1st edition. IBM Corp. Item Number. 6183946 IBM Corp., IBM, (January 1984). "Disk Operating System User's guide (DOS Release 2.10)". 1st edition. Microsoft Corp. (100 pages including colour illustrations) Item Number. 6183947 IBM Corp., IBM, (January 1984). "Disk Operating System Manual (DOS Release 2.10)". 1st edition. Microsoft Corp. (574 looseleaf pages in 3 ring folder) Item No. 6183940 External links Origins of DOS, articles and manuals by Tim Paterson. Batfiles: The DOS batch file programming handbook "(...) An archive of carefully hand selected FREE [and abandoned] software for DOS." American inventions Disk operating systems

Operating System (OS)

Pick operating system The Pick operating system (often called just "the Pick system" or simply "Pick") is a demand-paged, multiuser, virtual memory, time-sharing computer operating system based around a MultiValue database. Pick is used primarily for business data processing. It is named after one of its developers, Richard A. (Dick) Pick. The term "Pick system" has also come to be used as the general name of all operating environments which employ this multivalued database and have some implementation of Pick/BASIC and ENGLISH/Access queries. Although Pick started on a variety of minicomputers, the system and its various implementations eventually spread to a large assortment of microcomputers, personal computers and mainframe computers. Overview The Pick operating system consists of a database, dictionary, query language, procedural language (PROC), peripheral management, multi-user management, and a compiled BASIC Programming language. The database is a 'hash-file' data management system. A hash-file system is a collection of dynamic associative arrays which are organized altogether and linked and controlled using associative files as a database management system. Being hash-file oriented, Pick provides efficiency in data access time. Originally, all data structures in Pick were hash-files (at the lowest level) meaning records are stored as associated couplets of a primary key to a set of values. Today a Pick system can also natively access host files in Windows or Unix in any format. A Pick database is divided into one or more accounts, master dictionaries, dictionaries, files, and sub-files, each of which is a hash-table oriented file. These files contain records made up of fields, sub-fields, and sub-sub-fields. In Pick, records are called items, fields are called attributes, and sub-fields are called values or sub-values (hence the present-day label "multivalued database"). All elements are variable-length, with field and values marked off by special delimiters, so that any file, record, or field may contain any number of entries of the lower level of entity. As a result, a Pick item (record) can be one complete entity (one entire invoice, purchase order, sales order, etc.), or is like a file on most conventional systems. Entities that are stored as 'files' in other common-place systems (e.g. source programs and text documents) must be stored as records within files on Pick. The file hierarchy is roughly equivalent to the common Unix-like hierarchy of directories, sub-directories, and files. The master dictionary is similar to a directory in that it stores pointers to other dictionaries, files and executable programs. The master dictionary also contains the command-line language. All files (accounts, dictionaries, files, sub-files) are organized identically, as are all records. This uniformity is exploited throughout the system, both by system functions, and by the system administration commands. For example, the 'find' command will find and report the occurrence of a word or phrase in a file, and can operate on any account, dictionary, file or sub-file. Each record must have a unique primary key which determines where in a file that record is stored. To retrieve a record, its key is hashed and the resultant value specifies which of a set of discrete "buckets" (called "groups") to look in for the record. Within a bucket, records are scanned sequentially. Therefore, most records (e.g. a complete document) can be read using one single disk-read operation. This same method is used to write the record back to its correct "bucket". In its initial implementation, Pick records were limited to 32 KB in total (when a 10 MB hard disk cost US$5000), although this limit was removed in the 1980s. Files can contain an unlimited number of records, but retrieval efficiency is determined by the number of records relative to the number of buckets allocated to the file. Each file may be initially allocated as many buckets as required, although changing this extent later may (for some file types) require the file to be quiescent. All modern multi-value databases have a special file-type which changes extent dynamically as the file is used. These use a technique called linear hashing, whose cost is proportional to the change in file size, not (as in typical hashed files) the file size itself. All files start as a contiguous group of disk pages, and grow by linking additional "overflow" pages from unused disk space. Initial Pick implementations had no index structures as they were not deemed necessary. Around 1990, a B-tree indexing feature was added. This feature makes secondary key look-ups operate much like keyed inquiries of any other database system: requiring at least two disk reads (a key read then a data-record read). Pick data files are usually two levels. The first level is known as the "dictionary" level and is mandatory. It contains: Dictionary itemsthe optional items that serve as definitions for the names and structure of the items in the data fork, used in reporting The data-level identifiera pointer to the second or "data" level of the file Files created with only one level are, by default, dictionary files. Some versions of the Pick system allow multiple data levels to be linked to one dictionary level file, in which case there would be multiple data-level identifiers in the dictionary file. A Pick database has no data typing, since all data is stored as characters, including numbers (which are stored as character decimal digits). Data integrity, rather than being controlled by the system, is controlled by the applications and the discipline of the programmers. Because a logical document in Pick is not fragmented (as it would be in SQL), intra-record integrity is automatic. In contrast to many SQL database systems, Pick allows for multiple, pre-computed field aliases. For example, a date field may have an alias definition for the format "12 Oct 1999", and another alias formatting that same date field as "10/12/99". File cross-connects or joins are handled as a synonym definition of the foreign key. A customer's data, such as name and address, are "joined" from the customer file into the invoice file via a synonym definition of "customer number" in the "invoice" dictionary. Pick record structure favors a non-first-normal-form composition, where all of the data for an entity is stored in a single record, obviating the need to perform joins. Managing large, sparse data sets in this way can result in efficient use of storage space. This is why these databases are sometimes called NF2 or NF-squared databases. History Pick was originally implemented as the Generalized Information Retrieval Language System (GIRLS) on an IBM System/360 in 1965 by Don Nelson and Richard (Dick) Pick at TRW, whose government contract for the Cheyenne Helicopter project required developing a database. It was supposed to be used by the U.S. Army to control the inventory of Cheyenne helicopter parts. Pick was subsequently commercially released in 1973 by Microdata Corporation (and its British distributor CMC) as the Reality Operating System now supplied by Northgate Information Solutions. McDonnell Douglas bought Microdata in 1981. Originally on the Microdata implementation, and subsequently implemented on all Pick systems, a BASIC language called Data/BASIC with numerous syntax extensions for smart terminal interface and database operations was the primary programming language for applications. A PROC procedure language was provided for executing scripts. A SQL-style language called ENGLISH allowed database retrieval and reporting, but not updates (although later, the ENGLISH command "REFORMAT" allowed updates on a batch basis). ENGLISH did not fully allow manipulating the 3-dimensional multivalued structure of data records. Nor did it directly provide common relational capabilities such as joins. This was because powerful data dictionary redefinitions for a field allowed joins via the execution of a calculated lookup in another file. The system included a spooler. A simple text editor for file-system records was provided, but the editor was only suitable for system maintenance, and could not lock records, so most applications were written with the other tools such as Batch, RPL, or the BASIC language so as to ensure data validation and allow record locking. By the early 1980s observers saw the Pick operating system as a strong competitor to Unix. BYTE in 1984 stated that "Pick is simple and powerful, and it seems to be efficient and reliable, too ... because it works well as a multiuser system, it's probably the most cost-effective way to use an XT". Dick Pick founded Pick & Associates, later renamed Pick Systems, then Raining Data,then () TigerLogic, and finally Rocket Software. He licensed "Pick" to a large variety of manufacturers and vendors who have produced different "flavors" of Pick. The database flavors sold by TigerLogic were D3, mvBase, and mvEnterprise. Those previously sold by IBM under the "U2" umbrella are known as UniData and UniVerse. Rocket Software purchased IBM's U2 family of products in 2010 and TigerLogic's D3 and mvBase family of products in 2014. In 2021, Rocket acquired OpenQM and jBASE as well. Dick Pick died of stroke complications in October 1994. Pick Systems often became tangled in licensing litigation, and devoted relatively little effort to marketing and improving its software. Subsequent ports of Pick to other platforms generally offered the same tools and capabilities for many years, usually with relatively minor improvements and simply renamed (for example, Data/BASIC became Pick/BASIC and ENGLISH became ACCESS). Licensees often developed proprietary variations and enhancements (for example, Microdata created their own input processor called ScreenPro). Derivative and related products The Pick database was licensed to roughly three dozen licensees between 1978 and 1984. Application-compatible implementations evolved into derivatives and also inspired similar systems. Reality – The first implementation of the Pick database was on a Microdata platform using firmware and called Reality. The first commercial release was in 1973. Microdata acquired CMC Ltd. in the early 80s and were based in Hemel Hempstead, England. The Microdata implementations ran in firmware, so each upgrade had to be accompanied by a new configuration chip. Microdata itself was eventually bought by McDonnell Douglas Information Systems. Pick and Microdata sued each other for the right to market the database, the final judgment being that they both had the right. In addition to the Reality Sequoia and Pegasus series of computers, Microdata and CMC Ltd. sold the Sequel (Sequoia) series which was a much larger class able to handle over 1000 simultaneous users. The earlier Reality minicomputers were known to handle well over 200 simultaneous users, although performance was slow and it was above the official limit. Pegasus systems superseded Sequoia and could handle even more simultaneous users than its predecessors. The modern version of this original Pick implementation is owned and distributed by Northgate Information Solutions Reality. Ultimate – The second implementation of the Pick database was developed in about 1978 by a New Jersey company called The Ultimate Corp, run by Ted Sabarese. Like the earlier Microdata port, this was a firmware implementation, with the Pick instruction set in firmware and the monitor in assembly code on a Honeywell Level 6 machine. The system had dual personalities in that the monitor/kernel functions (mostly hardware I/O and scheduling) were executed by the native Honeywell Level 6 instruction set. When the monitor "select next user" for activation control was passed to the Honeywell WCS (writable control store) to execute Pick assembler code (implemented in microcode) for the selected process. When the user's time slice expired control was passed back to the kernel running the native Level 6 instruction set. Ultimate took this concept further with the DEC LSI/11 family of products by implementing a co-processor in hardware (bit-slice, firmware driven). Instead of a single processor with a WCS microcode enhanced instruction set, this configuration used two independent but cooperating CPUs. The LSI11 CPU executed the monitor functions and the co-processor executed the Pick assembler instruction set. The efficiencies of this approach resulted in a 2× performance improvement. The co-processor concept was used again to create a 5×, 7×, and dual-7× versions for Honeywell Level 6 systems. Dual ported memory with private busses to the co-processors were used to increase performance of the LSI11 and Level 6 systems. Another version used a DEC LSI-11 for the IOP and a 7X board. Ultimate enjoyed moderate success during the 1980s, and even included an implementation running as a layer on top of DEC VAX systems, the 750, 780, 785, and later the MicroVAX. Ultimate also had versions of the Ultimate Operating System running on IBM 370 series systems (under VM and native) and also the 9370 series computers. Ultimate was renamed Allerion, Inc., before liquidation of its assets. Most assets were acquired by Groupe Bull, and consisted of mostly maintaining extant hardware. Bull had its own problems and in approximately 1994 the US maintenance operation was sold to Wang. Prime INFORMATION – Devcom, a Microdata reseller, wrote a Pick-style database system called INFORMATION in FORTRAN and assembler in 1979 to run on Prime Computer 50-series systems. It was then sold to Prime Computer and renamed Prime INFORMATION. It was subsequently sold to VMark Software Inc. This was the first of the guest operating environment implementations. INFO/BASIC, a variant of Dartmouth BASIC, was used for database applications. UniVerse – Another implementation of the system, called UniVerse, was created by VMark Software and operated under Unix and Microsoft Windows. This was the first one to incorporate the ability to emulate other implementations of the system, such as Microdata's Reality Operating System, and Prime INFORMATION. Originally running on Unix, it was later also made available for Windows. It now is owned by Rocket Software. (The systems developed by Prime Computer and VMark are now owned by Rocket Software and referred to as "U2".) UniData – Very similar to UniVerse, but UniData had facilities to interact with other Windows applications. It is also owned and distributed by Rocket Software. PI/open – Prime Computer rewrote Prime INFORMATION in C for the Unix-based systems it was selling, calling it PI+. It was then ported to other Unix systems offered by other hardware vendors and renamed PI/open. Applied Digital Data Systems (ADDS) – This was the first implementation to be done in software only, so upgrades were accomplished by a tape load, rather than a new chip. The "Mentor" line was initially based on the Zilog Z-8000 chipset and this port set off a flurry of other software implementations across a wide array of processors with a large emphasis on the Motorola 68000. Fujitsu Microsystems of America – Another software implementation, existing in the late 1980s. Fujitsu Microsystems of America was acquired by Alpha Microsystems on October 28, 1989. Pyramid – Another software implementation existing in the 1980s General Automation "Zebra" – Another software implementation existing in the 1980s Altos – A software implementation on an 8086 chipset platform launched around 1983. WICAT/Pick – Another software implementation existing in the 1980s Sequoia – Another software implementation, existing from 1984. Sequoia was most well known for its fault-tolerant multi-processor model, which could be dialed into with the user's permission and his switching terminal zero to remote with the key on the system consol. He could watch what was done by the support person who had dialed on his terminal 0, a printer with a keyboard. Pegasus came out in 1987. The Enterprise Systems business unit (which was the unit that sold Pick), was sold to General Automation in 1996/1997. Revelation – In 1984, Cosmos released a Pick-style database called Revelation, later Advanced Revelation, for DOS on the IBM PC. Advanced Revelation is now owned by Revelation Technologies, which publishes a GUI-enabled version called OpenInsight. jBASE – jBASE was released in 1991 by a small company of the same name in Hemel Hempstead, England. Written by former Microdata engineers, jBASE emulates all implementations of the system to some degree. jBASE compiles applications to native machine code form, rather than to an intermediate byte code. In 2015, cloud solutions provider Zumasys in Irvine, California, acquired the jBASE distribution rights from Mpower1 as well as the intellectual property from Temenos Group. On 14 Oct 2021, Zumasys announced they had sold their databases and tools, including jBASE to Rocket Software. UniVision – UniVision was a Pick-style database designed as a replacement for the Mentor version, but with extended features, released in 1992 by EDP in Sheffield, England. OpenQM – The only MultiValue database product available both as a fully supported non-open source commercial product and in open source form under the General Public License. OpenQM is available from its exclusive worldwide distributor, Zumasys. Caché – In 2005 InterSystems, the maker of Caché database, announced support for a broad set of MultiValue extensions, Caché for MultiValue. ONware – ONware equips MultiValue applications with the ability to use common databases such as Oracle and SQL Server. Using ONware, MultiValue applications can be integrated with relational, object, and object-relational applications. D3 – Pick Systems ported the Pick operating system to run as a database product utilizing host operating systems such as Unix, Linux, or Windows servers, with the data stored within the file system of the host operating system. Previous Unix or Windows versions had to run in a separate partition, which made interfacing with other applications difficult. The D3 releases opened the possibility of integrating internet access to the database or interfacing to popular word processing and spreadsheet applications, which has been successfully demonstrated by a number of users. The D3 family of databases and related tools is owned and distributed by Rocket Software. Through the implementations above, and others, Pick-like systems became available as database/programming/emulation environments running under many variants of Unix and Microsoft Windows. Over the years, many important and widely used applications have been written using Pick or one of the derivative implementations. In general, the end users of these applications are unaware of the underlying Pick implementation. Criticisms and comparisons Run-time environment Native Pick did not require an underlying operating system (OS) to run. This changed with later implementations when Pick was re-written to run on various host OS (Windows, Linux, Unix, etc.). While the host OS provided access to hardware resources (processor, memory, storage, etc.), Pick had internal processes for memory management. Object-oriented Caché addressed some of these problems. Networking in mvBase was not possible without an accompanying application running in the host OS that could manage network connections via TCP ports and relay them to Pick internal networking (via serial connection). Credentials and security Individual user accounts must be created within the Pick OS, and cannot be tied to an external source (such as local accounts on the host OS, or LDAP). User passwords are stored within the Pick OS as an encrypted value. The encrypted password can be "cracked" via brute force methods, but requires system access and Pick programming skills as part of the attack vector. The Rocket D3 implementation supports SSL file encryption. Expertise and support Companies looking to hire developers and support personnel for MultiValue-based (Pick-based) systems recognize that although developers typically do not learn the environment in college and university courses, developers can be productive quickly with some mentoring and training. Due to the efficient design and nature of the programming language (a variant of BASIC), the learning curve is generally considered low. Pick products such as D3, UniVerse, UniData, jBASE, Revelation, MVON, Caché, OpenQM, and Reality are still supported globally via well established distribution channels and resellers. The mvdbms Google Group is a useful place to start when looking for resources. (See mvdbms on Google Groups) See also MUMPS, the predecessor of Caché References Bibliography The REALITY Pocket Guide ; Jonathan E. Sisk ; Irvine, CA ; JES & Associates, Inc. ; 1981 The PICK Pocket Guide; Jonathan E. Sisk ; Irvine, CA ; Pick Systems ; 1982 Exploring The Pick Operating System ; Jonathan E. Sisk ; Steve VanArsdale ; Hasbrouck Heights, N.J. ; Hayden Book Co. 1985. The Pick Pocket Guide ; Jonathan E. Sisk ; Desk reference ed ; Hasbrouck Heights, N.J. ; Hayden Book Co. 1985. The Pick Perspective ; Ian Jeffrey Sandler ; Blue Ridge Summit, PA ; TAB Professional and Reference Books; 1989. Part of The Pick Library Series, Edited by Jonathan E. Sisk Pick for professionals : advanced methods and techniques ; Harvey Rodstein ; Blue Ridge Summit, PA ; TAB Professional and Reference Books; 1990. Part of The Pick Library Series, Edited by Jonathan E. Sisk Encyclopedia PICK (EPICK) ; Jonathan E. Sisk ; Irvine, CA ; Pick Systems ; 1992 Le Système d'exploitation PICK ; Malcolm Bull ; Paris: Masson, 1989. The Pick operating system ; Joseph St John Bate; Mike Wyatt; New York : Van Nostrand Reinhold, 1986. The Pick operating system ; Malcolm Bull ; London ; New York : Chapman and Hall, 1987. Systeme pick ; Patrick Roussel, Pierre Redoin, Michel Martin ; Paris: CEdi Test, 1988. Advanced PICK et UNIX : la nouvelle norme informatique ; Bruno Beninca; Aulnay-sous-Bois, Seine-Saint-Denis ; Relais Informatique International, 1990. Le systeme PICK : mode d'emploi d'un nouveau standard informatique ; Michel Lallement, Jeanne-Françoise Beltzer; Aulnay-sous-Bois, Seine-Saint-Denis ; Relais Informatique International, 1987. The Pick operating system : a practical guide ; Roger J Bourdon; Wokingham, England ; Reading, Mass. : Addison-Wesley, 1987. Le Système d'éxploitation : réalités et perspectives ; Bernard de Coux; Paris : Afnor, 1988. Pick BASIC : a programmer's guide ; Jonathan E Sisk;Blue Ridge Summit, PA : TAB Professional and Reference Books, 1987. Part of The Pick Library Series, Edited by Jonathan E. Sisk Pick BASIC : a reference guide ; Linda Mui; Sebastopol, CA : O'Reilly & Associates, 1990. Programming with IBM PC Basic and the Pick database system ; Blue Ridge Summit, PA : TAB Books, 1990. Part of The Pick Library Series, Edited by Jonathan E. Sisk An overview of PICK system ;Shailesh Kamat; 1993. Pick: A Multilingual Operating System ; Charles M. Somerville; Computer Language Magazine, May 1987, p. 34. Encyclopedia Pick; Jonathan E. Sisk; Pick Systems, June 1991 External links Photo of Dick Pick in his anti-gravity boots on the cover of Computer Systems News, 1983. Pick/BASIC: A Programmer's Guidethe full text of the first and most widely read textbook by Pick educator and author Jonathan E. Sisk. Life the Universe and Everything: introduction to and online training course in Universe developed by Pick software engineer Manny Neira. Video: "History of the PICK System" made in 1990 Pick Publications Database 1987 Interview with Dick Pick in the Pick Pavilion at COMDEX 1990 Interview with Dick Pick in the Pick Pavilion at COMDEX 1990 Interview with Jonathan Sisk in the Pick Pavilion at COMDEX 1991 Pick Rap Show at COMDEX, co-written by Jonathan Sisk and John Treankler 1992 Video of Dick and Zion Pick, who appeared in the Ross Perot campaign rally - includes entire unedited Perot speech An insightful early history of the Pick System, by Chandru Murthi, who was there at the time 1984 PC Magazine article "Choosing the Pick of the Litter", by Jonathan E. Sisk and Steve VanArsdale Database Management Approach to Operating Systems Development, by Richard A. Pick Chapter 5 of New Directions for Database Systems, Gad Ariav, James Clifford editors Doing More With Less Hardware, Computer History Museum piece on Pick 1965 software Data processing Legacy systems Proprietary database management systems Proprietary operating systems Assembly language software Time-sharing operating systems X86 operating systems 68k architecture

Operating System (OS)

OS4000 OS4000 is a proprietary operating system introduced by GEC Computers Limited in 1977 as the successor to GEC DOS, for its range of GEC 4000 series 16-bit, and later 32-bit, minicomputers. OS4000 was developed through to late 1990s, and has been in a support-only mode since then. History The first operating systems for the GEC 4000 series were COS (Core Operating System) and DOS (Disk Operating System). These were basically single-user multi-tasking operating systems, designed for developing and running Process control type applications. OS4000 was first released around 1977. It reused many of the parts of DOS, but added multi-user access, OS4000 JCL Command-line interpreter, Batch processing, OS4000 hierarchical filesystem (although on-disk format very similar to the non-hierarchical DOS filesystem). OS4000 JCL was based on the Cambridge University Phoenix command interpreter. OS4000 Rel 3 arrived around 1980, and included Linked-OS — support for Linked OS4000 operating systems to enable multi-node systems to be constructed. The main customer for this was the central computing service of University College London (Euclid), where a multi-node system consisting of a Hub file server and multiple Rim multi-access compute server systems provided service for over 100 simultaneous users. Linked-OS was also used to construct fail-over Process control systems with higher resilience. OS4000 Rel 4 arrived around 1983, and upped the maximum number of user modules to 150 (again, mainly for the University College London Euclid system), together with an enhanced Batch processing system. It also included support for the GEC 4090 processor, which introduced a 32-bit addressing mode. OS4000 Rel 5 introduced a modified version of the OS4000 filesystem called CFSX, in order to allow easier use of larger disks. The initial Rel 5 only supported the CFSX filesystem, but support for the original CFS1 filesystem was reintroduced as well quite quickly. OS4000 Rel 6 introduced support for dual processor systems (GEC 4190D). OS4000 was developed in the UK at GEC Computers Borehamwood offices in Elstree Way, and at GEC Computers Dunstable Development Centre in Woodside Estate, Dunstable. Architecture The architecture of OS4000 is very heavily based around the features of the platform it runs on, the GEC 4000 series minicomputers, and these are rather unusual. They include a feature called Nucleus, which is a combination of a hardware- and firmware-based kernel, which cannot be altered under program control. This means that many of the features typically found in operating system kernels do not need to be included in OS4000, as the underlying platform performs these functions instead of the operating system. Consequently, there is no provision for running privileged mode code on the platform—all OS4000 operating system code runs as processes. Nucleus supports up to 256 processes, and schedules these automatically using a fixed priority scheme. OS4000 lives entirely within these processes. A set of system tables are used to configure Nucleus, and access to these system tables can be granted to processes which need to alter the configuration of Nucleus, e.g. to load new programs into processes, adjust the Nucleus scheduling for time-shared processes, etc. The system tables tell Nucleus which processes are permitted to communicate with each other, and these are updated as processes are created and destroyed, e.g. when users login and logout. All I/O is performed directly from processes, and the system tables identify which processes have access to which peripherals and handle peripheral interrupts. For example, a device driver for a disk controller is a process, which is responsible for issuing commands through Nucleus to the disk controller, and handling the interrupts passed back from the disk controller via Nucleus, and the system tables will explicitly state that process has access to that disk controller. The system tables will not grant this device driver access to any other peripherals. In the event of a process stopping or crashing, Nucleus looks up its owner process in the system tables, and informs it. The owner process can then take the decision to let the system continue running without that process, or to take out the system (like a Unix panic), or to take some action such as reload and/or restart the process. Functions such as filesystems, store allocation, terminal drivers, timing services, etc. also exist as separate processes. Nucleus implements a segmented memory system, with processes having their access to memory segments defined by the system tables, which is maintained by OS4000. OS4000 provides a memory system which handles both store-resident memory, and virtual memory backed by disk which is known as overlay, with overlaying being performed at the segment level. OS4000 also inherited grouped segments from DOS, where a group of segments were to be overlaid and retrieved as a single group, but this feature was very little used in OS4000. A process may use any mixture of resident and overlayable segments, although a process performing real-time tasks would normally be designed to only use resident segments. OS4000 supports a fully mixed set of process scheduling within the same system, from hard real-time processes, through soft real-time, time-shared, and background. Given that OS4000 also includes full program development and test/debug facilities, this made OS4000 ideal for developing and deploying real-time applications such as process control and high speed (at the time) data communications all within one system. Filesystem OS4000 uses its own proprietary filesystem. The filesystem is extent based, and variable block size — different files can be created with different blocksizes, ranging from 256 bytes to 16,384 bytes in 256-byte multiples. The filesystem is hierarchical, with components limited to 8 characters and the "." (period) used as the component separator. OS4000 JCL limits characters in file path components to upper case letters and numbers only. Each file path starts with a context pointer which is a name which refers to a position in a filesystem, followed by zero or more catalogues (equivalent to Unix directories), and ending with a filename. Each disk on the system contains a separate and independent filesystem, and the volume name of a disk is the same as the name of its top level catalogue or master catalogue. There must be one disk mounted with a volume name of SYSTEM which contains specific files required by OS4000. In larger systems, there will usually be additional disks containing user files, data files, etc. although these can all coexist on the SYSTEM disk, space permitting. Users are each given a set of initial context pointers which each point to a catalogue on a filesystem, and users can only see the filesystem hierarchies below their initial context pointers. Systems are usually configured so that unprivileged users cannot see other users files or the system's files, except for the system executables held in SYS. By convention, an area called POOL is available for all users, and enables the transfer/sharing of files. Files in an OS4000 filesystem are typed, which means that the filesystem can hold several different types of file, and understands how the contents are structured. Most common are logical files which contain a record structure. These are split into sequential and random files, with random files having all records the same length to enable seeking to record numbers. Finally, text and binary files are distinguished, mainly to prevent applications which expect textual data from accidentally using a binary file. This results in a set of logical file types identified by three letters, e.g. Logical Sequential Text is LST. The logical file types are LST, LSB, LRT, LRB. The converse to logical files are physical files, which are accessed block at a time, and these are known as Physical Random Binary (PRB) files. File types PST, PSB, PRT also exist in theory, but have the same capabilities as PRB and are not generally used. Additionally, there is a Logical Indexed Sequential (LIS) filetype, which is an ISAM file and always appears to be sorted on its key field, and a Byte stream (BYT) filetype, which was added in Rel 6.5 to better support the OS4000 NFS server. A filetype CAT is used to hold catalogues—it is actually the same as an LSB file, but can only be modified by the filesystem itself. In addition to files and catalogues, there are 3 types of symbolic links. References (REF) can be created to point to another file or catalogue which creator of the REF can see through an initial context pointer, in either the same filesystem or another filesystem. Off Disk Pointers (ODP) are similar to references but can be created to point to a file or catalogue which cannot be seen through any initial context pointers, and creating an ODP is a privileged operation only available to the system manager. Support for Unix style symlinks (arbitrary text stored in a catalogue) was added in Rel 6.5 to better support the OS4000 NFS server, but symlinks can only be created and are only visible from NFS clients. OS4000 also provides a non-hierarchical temporary filesystem. This supports exactly the same types of file as permanent filesystems, except for CAT, REF, ODP, and symlinks. The file contents are stored in dedicated temporary filing disk regions, but the file metadata is stored in memory. Each logged in user has a private temporary filing name space which cannot be seen by any other logged in user (nor even another logged in user with the same username). A user's temporary files are deleted when the user logs out (and implicitly if the system is rebooted). Temporary filenames start with a percent "%" or ampersand "&" and are limited to 8 characters. Multi-access Environment The following shows a short Multi-access login session: In this case, user SMAN has logged in and issued the EXAMINE command. Then the session has been left to timeout through inactivity. When a user logs in, the OS4000 JCL command interpreter SYS.COMM is loaded into the user's COMM process and started. This reads commands from the terminal. A number of system commands are built into SYS.COMM. In the case of a command which isn't built in, executable binary files are loaded into the USER process and run, and text JCL files are opened and processed directly by SYS.COMM itself. A user normally also gets an AIDA process which is privileged and used to load only trusted debugging programs. Main Applications Real-time Process Control accounts for over half of all the OS4000 systems deployed. Of these systems, steel production accounts for a significant proportion. The earlier of these Real-time Process Control systems were upgraded from DOS to OS4000. X.25 Packet Switches account for a significant proportion of systems (although earlier GEC X.25 Packet Switches ran a special operating system called NOS which was a cut down operating system halfway between DOS and OS4000). Civil Command and Control systems, e.g. Fire Service control systems interfacing the emergency telephone operator with the Fire Stations. Prestel (UK) and the public Videotex systems used in many other countries, and many private Viewdata systems. Multi-User Minicomputers, used in many Education and Research establishments. Ports OS4000 was ported to the GEC Series 63 minicomputer where it was known as OS6000. This required the addition of a software Nucleus emulation, as this was not a feature of the GEC Series 63 hardware. GEC Computers dropped OS6000, and the source code was given to Daresbury Laboratory who was the main user of it, and they continued to keep it in step with OS4000 releases for the lifetime of their two GEC Series 63 systems. See also GEC 4000 series minicomputers Babbage (programming language) GEC Computers Limited References Further reading External links GEC 4000 family, Which Computer?, May 1979 The Centre for Computing History Bullet III - A Part of UK Network History Proprietary operating systems Real-time operating systems Time-sharing operating systems GEC Computers 1977 software

Operating System (OS)

Atari DOS Atari DOS is the disk operating system used with the Atari 8-bit family of computers. Operating system extensions loaded into memory were required in order for an Atari computer to manage files stored on a disk drive. These extensions to the operating system added the disk handler and other file management features. The most important extension is the disk handler. In Atari DOS 2.0, this was the File Management System (FMS), an implementation of a file system loaded from a floppy disk. This meant at least an additional RAM was needed to run with DOS loaded. Versions There were several versions of Atari DOS available, with the first version released in 1979. Atari was using a cross assembler with Data General AOS. DOS 1.0 In the first version of DOS from Atari all commands were only accessible from the menu. It was bundled with the 810 disk drives. This version was entirely memory resident, which made it fast but occupied memory space. DOS 2.0 Also known as DISK OPERATING SYSTEM II VERSION 2.0S The second, more popular version of DOS from Atari was bundled with the 810 disk drives and some early 1050 disk drives. It is considered to be the lowest common denominator for Atari DOSes, as any Atari-compatible disk drive can read a disk formatted with DOS 2.0S. DOS 2.0S consisted of DOS.SYS and DUP.SYS. DOS.SYS was loaded into memory, while DUP.SYS contained the disk utilities and was loaded only when the user exited to DOS. In addition to bug fixes, DOS 2.0S featured improved NOTE/POINT support and the ability to automatically run an Atari executable file named AUTORUN.SYS. Since user memory was erased when DUP.SYS was loaded, an option to create a MEM.SAV file was added. This stored user memory in a temporary file (MEM.SAV) and restored it after DUP.SYS was unloaded. The previous menu option from DOS 1.0, N. DEFINE DEVICE, was replaced with N. CREATE MEM.SAV in DOS 2.0S. Version 2.0S was for single-density disks, 2.0D was for double-density disks. 2.0D shipped with the 815 Dual Disk Drive, which was both expensive and incompatible with the standard 810, and thus sold only a small number; making DOS version 2.0D rare and unusual. DOS 3 A new version of DOS that came originally bundled with the 5.25-inch Atari 1050 disk drive. This made use of the new Enhanced Density (ED) capability (referred to by Atari as Dual Density.. This increased storage from 88 KB to 130 KB per disk. There was a single density (88 KB) formatting option to maintain compatibility with older Atari 810 disk drives. By organizing sectors into blocks, Atari was anticipating larger capacity floppy disks, but this resulted in incompatibility with DOS 2.0S. Files converted to DOS 3 could not be converted back to DOS 2.0. As a result, DOS 3 was extremely unpopular and did not gain widespread acceptance amongst the Atari user community. DOS 3 provided built-in help via the Atari HELP key and/or the inverse key. Help files needed to be present on the system DOS disk to function properly. DOS 3 also used special XIO commands to control disc operations within BASIC programs. DOS 2.5 Also known as DISK OPERATING SYSTEM II VERSION 2.5 Version 2.5 is an upgrade to 3.0. After listening to complaints by their customers, Atari released an improved version of their previous DOS. This allowed the use of Enhanced Density disks, and there was a utility to read DOS 3 disks. An additional option was added to the menu (P. FORMAT SINGLE) to format single-density disks. DOS 2.5 was shipped with 1050 disk drives and some early XF551 disk-drives. Included utilities were DISKFIX.COM, COPY32.COM, SETUP.COM and RAMDISK.COM. DOS 4.0 Codename during production: QDOS DOS 4.0 was designed for the never-released 1450XLD. The rights were returned to the author, Michael Barall, who placed it in the public domain. It was later published by Antic Software. DOS 4.0 used blocks instead of single sectors, and supported single, enhanced, and double density, as well as both single- and double-sided drives. DOS 4.0 was not compatible with DOS 2 or 3 disks but could read files from them. It also did not automatically switch densities, and it was necessary to go to the menu and manually select the correct density. DOS XE Codename during production: ADOS DOS XE supported the double-density and double-sided capabilities of the Atari XF551 drive, as well as its burst I/O. DOS XE used a new disk format which was incompatible with DOS 2.0S and DOS 2.5, requiring a separate utility for reading older 2.0 files. It also required bank-switched RAM, so it did not run on the 400/800 machines. It supported date-stamping of files and sub-directories. DOS XE was the last DOS made by Atari for the Atari 8-bit family. Third-party DOS programs Many of these DOSes were released by manufacturers of third-party drives, anyone who made drive modifications, or anyone who was dissatisfied with the available DOSes. Often, these DOSes could read disks in higher densities, and could set the drive to read disks faster (using Warp Speed or Ultra-Speed techniques). Most of these DOSes (except SpartaDOS) were DOS 2.0 compatible. DOS 2.6 Someone in the Atari hacker community modified DOS 2.0 to add a few features and allow the use of dual density disk drives, with the "look and feel" of DOS 2.0. One new feature added was "RADIX", which one could use to translate hexadecimal numbers to base 10 or base 10 to hex. SmartDOS Menu driven DOS that was compatible with DOS 2.0. Among the first third-party DOS programs to support double-density drives. Many enhancements including sector copying and verifying, speed checking, turning on/off file verifying and drive reconfiguration. Published by Rana Systems. Written by John Chenoweth and Ron Bieber, last version 8.2D. OS/A+ and DOS XL DOS produced by Optimized Systems Software. Compatible with DOS 2.0 - Allowed the use of Double Density floppies. Unlike most ATARI DOSses, this used a command line instead of a menu. DOS XL provided a menu program in addition to the command line. SuperDOS This DOS could read SS/SD, SS/ED, SS/DD and DS/DD disks, and made use of all known methods of speeding up disk-reads supported by the various third-party drive manufacturers. Published by Technical Support. Written by Paul Nicholls. Top-DOS Menu driven DOS with enhanced features. Sorts disk directory listings and can set display options. File directory can be compressed. Can display deleted files and undelete them. Some advanced features required a proprietary TOP-DOS format. Published by Eclipse Software. Written by R. K. Bennett. Turbo-DOS This DOS supports Turbo 1050, Happy, Speedy, XF551 and US Doubler highspeed drives. XL/XE only. Published by Martin Reitershan Computertechnik. Written by Herbert Barth and Frank Bruchhäuser. MyDOS This DOS adds the ability to use sub-directories, and supports hard-drives. Published by Wordmark Systems, includes complete source code. SpartaDOS This DOS used a command-line interface. Was not compatible with DOS 2.0, but could read DOS 2.0 disks. Supports subdirectories and hard drives being capable of handling filesystems sized up to 16 MB. Included the capability to create primitive batch files. SpartaDOS X A more sophisticated version of SpartaDOS, which strongly resembles MS-DOS in its look and feel. It was shipped on a 64 KB ROM cartridge. RealDOS A SpartaDOS compatible DOS (in fact, a renamed version of SpartaDOS 3.x, due to legal reasons). RealDOS is Shareware by Stephen J. Carden and Ken Ames. BW-DOS A SpartaDOS compatible DOS, the last version 1.30 was released in December 1995. It has a much lower memory footprint compared to the original SpartaDOS and does not use the RAM under the ROM of XL/XE machines, allowing it to be used on the older Atari 400/800 models. BW-DOS is Freeware by Jiří Bernasek. XDOS XDOS is Freeware by Stefan Dorndorf. Disk formats A number of different formats existed for Atari disks. Atari DOS 2.0S, single-sided, single-density disk had 720 sectors divided into 40 tracks. After formatting, 707 sectors were free. Each 128-byte sector used the last 3 bytes for housekeeping data (bytes used, file number, next sector), leaving 125 bytes for data. This meant each disk held 707 × 125 = 88,375 bytes of user data. The single-density disk holding a mere 88 KB per side remained the most popular Atari 8-bit disk format throughout the series' lifetime, and almost all commercial software continued to be sold in that format (or variants of it modified for copy protection), since it was compatible with all Atari-made disk drives. Single-Sided, Single-Density: 40 tracks with 18 sectors per track, 128 bytes per sector. 90 KB capacity. Single-Sided, Enhanced-Density: 40 tracks with 26 sectors per track, 128 bytes per sector. 130 KB capacity. Readable by the 1050 and the XF551. Single-Sided, Double-Density: 40 tracks with 18 sectors per track, 256 bytes per sector. 180 KB capacity. Readable by the XF551, the 815, or modified/upgraded 1050. Double-Sided, Double-Density: 80 tracks (40 tracks per side) with 18 sectors per track, 256 bytes per sector. 360 KB capacity. Readable by the XF551 only. Percom standard In 1978, Percom established a double-density layout standard which all other manufacturers of Atari-compatible disk drives such as Indus, Amdek, and Rana —except Atari itself— followed. A configuration block of 12 bytes defines the disk layout. References Notes (Online version) Mapping the Atari, Revised Edition by Ian Chadwick External links Atari DOS Reference Manual — Reference manual for DOS 3. Antic Vol.4 No.3 Everything You Wanted To Know About Every DOS Atari Dos 4 (aka ANTIC Dos aka QDOS) Documentation on Atari DOS 4 MyDOS Source Code from Wordmark Systems. Atari 8-bit family software Atari operating systems Disk operating systems Discontinued operating systems 1979 software

Operating System (OS)

Mobile operating system A mobile operating system is an operating system for mobile phones, tablets, smartwatches, 2-in-1 PCs, smart speakers, or other mobile devices. While computers such as typical laptops are 'mobile', the operating systems used on them are generally not considered mobile ones, as they were originally designed for desktop computers that historically did not have or need specific mobile features. This distinction is becoming blurred in some newer operating systems that are hybrids made for both uses. Mobile operating systems combine features of a personal computer operating system with other features useful for mobile or handheld use, and usually including a wireless inbuilt modem and SIM tray for telephony and data connection. By Q1 2018, over 383 million smartphones were sold with 86.2 percent running Android and 12.9 percent running iOS. Android alone is more popular than the popular desktop operating system Microsoft Windows, and in general smartphone use (even without tablets) outnumbers desktop use. Mobile devices, with mobile communications abilities (e.g., smartphones), contain two mobile operating systemsthe main user-facing software platform is supplemented by a second low-level proprietary real-time operating system which operates the radio and other hardware. Research has shown that these low-level systems may contain a range of security vulnerabilities permitting malicious base stations to gain high levels of control over the mobile device. Mobile operating systems have majority use since 2017 (measured by web use); with even only the smartphones running them (excluding tablets) having majority use, more used than any other kind of device. Thus traditional desktop OS is now a minority-used kind of OS; see usage share of operating systems. However, variations occur in popularity by regions, while desktop-minority also applies on some days in countries such as United States and United Kingdom. Timeline Mobile operating system milestones mirror the development of mobile phones, PDAs, and smartphones: Pre-1993 1973–1993 – Mobile phones use embedded systems to control operation. 1993–1999 1993 April – PenPoint OS by GO Corporation becomes available on the AT&T EO Personal Communicator. August – Apple launches Newton OS running on their Newton series of portable computers. 1994 March – Magic Cap OS by General Magic is first introduced on the Sony Magic Link PDA. August – The first smartphone, the IBM Simon, has a touchscreen, email, and PDA features. 1996 March – The Palm Pilot 1000 personal digital assistant is introduced with the Palm OS mobile operating system. August – Nokia releases the Nokia 9000 Communicator running an integrated system based on the PEN/GEOS 3.0 OS from Geoworks. 1997 – EPOC32 first appears on the Psion Series 5 PDA. Release 6 of EPOC32 will later be renamed to Symbian OS. 1998 – Symbian Ltd. is formed as a joint venture by Psion, Ericsson, Motorola, and Nokia, Psion's EPOC32 OS becomes Symbian's EPOC operating system, and is later renamed to Symbian OS. Symbian's OS was used by those companies and several other major mobile phone brands, but especially Nokia. 1999 June – Qualcomm's pdQ becomes the first smartphone with Palm OS. October – Nokia S40 Platform is officially introduced along with the Nokia 7110, the first phone with T9 Predictive text input and a Wireless Application Protocol (WAP) browser for accessing specially formatted Internet data. 2000s 2000 – The Ericsson R380 is released with EPOC32 Release 5, marking the first use on a phone of what's to become known as Symbian OS (as of Release 6). 2001 June – Nokia's Symbian Series 80 platform is first released on the Nokia 9210 Communicator This is the first phone running an OS branded as Symbian, and the first phone using that OS that allows user installation of additional software. September – Qualcomm's Binary Runtime Environment for Wireless (BREW) platform on their REX real-time operating system (RTOS) is first released on the Kyocera QCP-3035. 2002 March BlackBerry releases its first smartphone, running Java 2 Micro Edition (J2ME). UIQ is first released, at v2.0, on Symbian OS, and becomes available later in the year on the Sony Ericsson P800, the successor to the Ericsson R380. June Microsoft's first Windows CE (Pocket PC) smartphones are introduced. Nokia's Symbian Series 60 (S60) platform is released with the Nokia 7650, Nokia's first phone with a camera and Multimedia Messaging Service (MMS). S60 would form the basis of the OS on most of Nokia's smartphones until 2011, when they adopted Microsoft's Windows Phone 7. S60 was also used on some phones from Samsung and others, and later by Sony Ericsson after the consolidation of different Symbian UI variants in 2008. October – The Danger Hiptop (T-Mobile Sidekick in U.S.) is first released by Danger, Inc., running DangerOS. 2003 – Motorola introduces first linux based cellphone Motorola A760 base on Linux MontaVista distribution. 2005 May – Microsoft announces Windows Mobile 5.0. November – Nokia introduces Maemo OS on the first, small Internet tablet, the N770, with a 4.13" screen. 2007 January – Apple's iPhone with iOS (named "iPhone OS" for its first three releases) is introduced as a "widescreen iPod," "mobile phone," and "Internet communicator". February – Microsoft announces Windows Mobile 6.0. May – Palm announces the Palm Foleo, a "Mobile Companion" device similar to a subnotebook computer, running a modified Linux kernel and relying on a companion Palm Treo smartphone to send and retrieve mail, as well as provide data connectivity when away from WiFi. Palm canceled Foleo development on September 4, 2007, after facing public criticism. June - World's very first iPhone is released in the United States. November – Open Handset Alliance (OHA) is established, led by Google with 34 members (HTC, Sony, Dell, Intel, Motorola, Samsung, LG, etc.) 2008 February – LiMo Foundation announces the first phones running the LiMo mobile Linux distribution, from Motorola, NEC, Panasonic Mobile, and Samsung, released later in the year. The LiMo Foundation later became the Tizen Association and LiMo was subsumed by Tizen. June – Nokia becomes the sole owner of Symbian Ltd. The Symbian Foundation was then formed to co-ordinate the future development of the Symbian platform among the corporations using it, in a manner similar to the Open Handset Alliance with Android. Nokia remained the major contributor to Symbian's code. July – Apple releases iPhone OS 2 with the iPhone 3G, making available Apple's App Store. October – OHA releases Android (based on Linux kernel) 1.0 with the HTC Dream (T-Mobile G1) as the first Android phone. November – Symbian^1, the Symbian Foundation's touch-specific S60-based platform (equivalent to S60 5th edition) is first released on Nokia's first touchscreen Symbian phone, the Nokia 5800 XpressMusic, with a resistive screen and a stylus. Symbian^1 being derived from S60 meant that support for UIQ disappeared and no further devices using UIQ were released. 2009 January Intel announces Moblin 2, specifically created for netbooks that run the company's Atom processor. In April 2009 Intel turned Moblin over to the Linux Foundation. Palm introduces webOS with the Palm Pre (released in June). The new OS is not backwards compatible with their previous Palm OS. February Palm announces that no further devices with Palm OS are going to be released by the company. (The last was the Palm Centro, released October 14, 2007.) Microsoft announces Windows Mobile 6.5, an "unwanted stopgap" update to Windows Mobile 6.1 intended to bridge the gap between version 6.1 and the then yet-to-be released Windows Mobile 7 (later canceled in favor of Windows Phone 7). The first devices running it appeared in late October 2009. May – DangerOS 5.0 becomes available, based on NetBSD. June – Apple releases iPhone OS 3 with the iPhone 3GS. November – Nokia releases the Nokia N900, its first and only smartphone running the Maemo OS intended for "handheld computers...with voice capability," while stating that they remain focused on Symbian S60 as their smartphone OS. (Nokia had previously released three Mobile Internet devices running Maemo, without cellular network connectivity.) 2010s 2010 February MeeGo is announced, a mobile Linux distribution merging Maemo from Nokia and Moblin from Intel and Linux Foundation, to be hosted by Linux Foundation. MeeGo is not backwards compatible with any previous operating system. Samsung introduces the Bada OS and shows the first Bada smartphone, the Samsung S8500. It's later released in May 2010. April Apple releases the iPad (first generation) with iPhone OS 3.2. This is the first version of the OS to support tablet computers. For its next major version (4.0) iPhone OS will be renamed iOS. HP acquires Palm in order to use webOS in multiple new products, including smartphones, tablets, and printers, later stating their intent to use it as the universal platform for all their devices. May – Microsoft Kin phone line with KIN OS (based on Windows CE and a "close cousin" to Windows Phone) become available. June – Apple releases iOS 4, renamed from iPhone OS, with the iPhone 4. July – Microsoft Kin phones and KIN OS are discontinued. September Apple releases a variant of iOS powering the new 2nd generation Apple TV. Symbian^3 is first released on the Nokia N8. This would be Nokia's last flagship device running Symbian (though not their last Symbian phone), before switching to Windows Phone 7 for future flagship phones. The Danger Hiptop line and DangerOS are discontinued as a result of Microsoft's acquisition of Danger, Inc. in 2008. November Nokia assumes full control over Symbian as the Symbian Foundation disintegrates. Windows Phone OS is released on Windows Phone 7 phones by HTC, LG, Samsung, and Dell. The new OS is not backwards compatible with the prior Windows Mobile OS. 2011 February Android 3.0 (Honeycomb), the first version to officially support tablet computers, is released on the Motorola Xoom. Nokia abandons the Symbian OS and announces that it would use Microsoft's Windows Phone 7 as its primary smartphone platform, while Symbian would be gradually wound down. April – BlackBerry Tablet OS, based on QNX Neutrino is released on the BlackBerry PlayBook. July Mozilla announces their Boot to Gecko project (later named Firefox OS) to develop an OS for handheld devices emphasizing standards-based Web technologies, similar to webOS. webOS 3.0, the first version to support tablet computers, is released on the HP TouchPad. August – HP announces that webOS device development and production lines would be halted. The last HP webOS version, 3.0.5, is released on January 12, 2012. September MeeGo is introduced with the limited-release Nokia N9, Nokia's first and only consumer device to use the OS. (A small number of the Nokia N950, a MeeGo phone available only to developers, were released in mid-2011.) After Nokia's abandonment of MeeGo, Intel and the Linux Foundation announce a partnership with Samsung to launch Tizen, shifting their focus from MeeGo (Intel and Linux Foundation) and Bada (Samsung) during 2011 and 2012. October Apple releases iOS 5 with the iPhone 4S, integrating the Siri voice assistant. The Mer project is announced, based on an ultra-portable core for building products, composed of Linux, HTML5, QML, and JavaScript, which is derived from the MeeGo codebase. November – Fire OS, a fork of the Android operating system, is released by Amazon.com on the Kindle Fire tablet. 2012 May – Nokia releases the Nokia 808 PureView, later confirmed (in January 2013) to be the last Symbian smartphone. This phone was followed by a single last Symbian software update, "Nokia Belle, Feature Pack 2," later in 2012. July Finnish start-up Jolla, formed by former Nokia employees, announces that MeeGo's community-driven successor Mer would be the basis of their new Sailfish smartphone OS. Mozilla announces that the project formerly named Boot to Gecko (which is built atop an Android Linux kernel using Android drivers and services; however it uses no Java-like code of Android) is now Firefox OS (since discontinued) and has several handset OEMs on board. August – Samsung announces they won't ship further phones using their Bada OS, instead focusing on Windows Phone 8 and Android. September – Apple releases iOS 6 with the iPhone 5. 2013 January – BlackBerry releases their new operating system for smartphones, BlackBerry 10, with their Q10 and Z10 smartphones. BlackBerry 10 is not backwards compatible with the BlackBerry OS used on their previous smartphones. February – HP sells webOS to LG. September – Apple releases iOS 7 with the iPhone 5S and iPhone 5C. October Canonical announces Ubuntu Touch, a version of the Linux distribution expressly designed for smartphones. The OS is built on the Android Linux kernel, using Android drivers and services, but does not use any of the Java-like code of Android. Google releases Android KitKat 4.4. November – Jolla releases Sailfish OS on the Jolla smartphone. 2014 February Microsoft releases Windows Phone 8.1 Nokia introduces their Nokia X platform OS as an Android 4.1.2 Jelly Bean fork on the Nokia X family of smartphones. Similar to Amazon.com's Fire OS, it replaces Google's apps and services with ones from Nokia (such as HERE Maps, Nokia Xpress and MixRadio, and Nokia's own app store) and Microsoft (such as Skype and Outlook), with a user interface that mimics the Windows Phone UI. After the acquisition of Nokia's devices unit, Microsoft announced in July 2014 that no more Nokia X smartphones would be introduced, marking the end of the platform just a few months later. August – The Samsung SM-Z9005 Z is the first phone released running Tizen, with v2.2.1 of the OS. September Apple releases iOS 8 with the iPhone 6 and 6 Plus. BlackBerry releases BlackBerry 10 version 10.3 with integration with the Amazon Appstore November – Google releases Android 5.0 "Lollipop" 2015 February – Google releases Android 5.1 "Lollipop". April LG releases the LG Watch Urbane LTE smartwatch running "LG Wearable Platform OS" based on webOS. This is a version of their Android Wear OS-based LG Watch Urbane, with added LTE connectivity. watchOS, based on iOS, is released by Apple with the Apple Watch. September Apple releases iOS 9 with the iPhone 6S and 6S Plus, iPad Pro, and iPad Mini 4, plus watchOS 2. tvOS 9 is also made distinct from iOS, with its own App Store, launching with Apple TV 4th generation. Google releases Android 6.0 "Marshmallow". October – BlackBerry announces that there are no plans to release new APIs and software development kits for BlackBerry 10, and future updates would focus on security and privacy enhancements only. November – Microsoft releases Windows 10 Mobile. 2016 February – Microsoft releases the Lumia 650, their last Windows 10 Mobile phone before discontinuing all mobile hardware production the following year. July – The BlackBerry Classic, the last device to date running a BlackBerry OS is discontinued. While BlackBerry Limited claimed to still be committed to the BlackBerry 10 operating system, they have since only shipped Android devices after releasing the BlackBerry Priv, their first Android smartphone in November 2015. August Google posts the Fuchsia source code on GitHub. Google releases Android 7.0 "Nougat". September – Apple releases iOS 10 with the iPhone 7 and 7 Plus, and watchOS 3 with the Apple Watch Series 1 and 2. November Tizen releases Tizen 3.0. BlackBerry releases BlackBerry 10 version 10.3.3. 2017 April Development of Ubuntu Touch is transferred from Canonical Ltd. to the UBports Foundation Samsung officially launches Android-based Samsung Experience custom firmware starting with version 8.1 on Samsung Galaxy S8. May Samsung announces Tizen 4.0 at Tizen Developer Conference 2017. August Google releases Android 8.0 "Oreo". September Apple releases iOS 11 with the iPhone 8 and 8 Plus and iPhone X, and watchOS 4 with the Apple Watch Series 3. October Microsoft announces that Windows 10 Mobile development is going into maintenance mode only, ending the release of any new features or functionality due to lack of market penetration and resultant lack of interest from app developers, and releases the final major update to it, the "Fall Creators Update." Cherry Mobile release CherryOS based on Android 2018 February Samsung releases Samsung Experience 9.0 based on Android "Oreo" 8.0 globally to Samsung Galaxy S8 and S8+. March Google and partners officially launches Android Go (based on Android "Oreo" 8.1 but tailored for low-end devices) with Nokia 1, Alcatel 1X, ZTE Tempo Go, General Mobile 8 Go, Micromax Bharat Go and Lava Z50. Google releases Android "9" as a developer preview. April Microsoft release Windows 10 Version 1803 "April 2018 Update". May Huawei release LiteOS version 2.1. August Google releases Android 9.0 "Pie". UBPorts released Ubuntu Touch OTA-14, upgrading the OS based on the Canonical's long-term support version of Ubuntu 16.04 LTS "Xenial Xerus". Xiaomi officially introduces MIUI for POCO for their Poco series smartphone. Samsung officially introduces Tizen 4.0 with the release of Samsung Galaxy Watch series. September Apple releases iOS 12 with the iPhone XS and XS Max, and watchOS 5 with Apple Watch Series 4. Huawei releases EMUI 9.0. October Microsoft releases Windows 10 Version 1809 "October 2018 Update". November Samsung announces the One UI as the latest version of the Samsung Experience UI. Amazon released Fire OS 6 to supported Fire HD devices. 2019 January Microsoft announces that support for Windows 10 Mobile would end on December 10, 2019, and that Windows 10 Mobile users should migrate to iOS or Android phones. June Apple announces iOS 13, watchOS 6, and iPadOS as a distinct variant of iOS. August Huawei announced the EMUI 10 under beta release. September Apple releases iOS 13 with the iPhone 11 series, watchOS 6 with Apple Watch Series 5, and iPadOS with the 7th generation iPad. Google releases Android 10. The Librem 5, the first phone running PureOS, is released. October Samsung announces the One UI 2.0 as the latest version of their Galaxy Smartphone and Smartwatch UI. November Microsoft release the Windows 10 November 10, 2019 Update. Current software platforms These operating systems often run atop baseband or other real time operating systems that handle hardware aspects of the phone. Android Android (based on the modified Linux kernel) is a mobile operating system developed by Google. The base system is open-source (and only the kernel copyleft), but the apps and drivers which provide functionality are increasingly becoming closed-source. Besides having the largest installed base worldwide on smartphones, it is also the most popular operating system for general purpose computers (a category that includes desktop computers and mobile devices), even though Android is not a popular operating system for regular (desktop) personal computers (PCs). Although the Android operating system is free and open-source software, in devices sold, much of the software bundled with it (including Google apps and vendor-installed software) is proprietary software and closed source. Android's releases before 2.0 (1.0, 1.5, 1.6) were used exclusively on mobile phones. Android 2.x releases were mostly used for mobile phones but also some tablets, Android 3.0 was a tablet-oriented release and does not officially run on mobile phones, while both phone and tablet compatibility was merged with Android 4.0. The current Android version is Android 12, released on October 4, 2021. ==== Android One ==== Android One is a software experience that runs on the unmodified Android operating system, which closely resembles those running on Pixel devices or previously, the Google Nexus program. Unlike most of the "stock" Androids running on the market, Android One UI closely resembles the Pixel UI, due to Android One being a software experience developed by Google and distributed to partners who signup for the program, such as Nokia Mobile(HMD) and Xiaomi. Thus, the overall UI is intended to be as clean as possible. OEM partners may tweak or add additional apps such as cameras to the firmware, otherwise most of the apps will be handled by Google proprietary apps. The update was handled by Google and will be internally tested by OEM before being distributed via OTA update to the end users. Android One version are same as AOSP, starting from Android 5.0 "Lollipop" BlackBerry Secure BlackBerry Secure is an operating system developed by BlackBerry, based on the Android Open Source Project (AOSP). Officially announced the name for their Android based front-end touch interface in August 2017, before the announcement, BlackBerry Secure was running on BlackBerry brand devices such as BlackBerry Priv, DTEK 50/60 and BlackBerry KeyOne. Currently, BlackBerry plan to license out the BlackBerry Secure to other OEM's. Current BlackBerry Secure version list BlackBerry Secure version 1.x (based on Android "Marshmallow" 6.x and "Nougat" 7.x) (initial release and minor UI update for devices that support Android Nougat) ColorOS ColorOS is a custom front-end touch interface, based on the Android Open Source Project (AOSP) and is developed by OPPO Electronics Corp. , OPPO officially releases ColorOS with every OPPO and Realme devices(Future Realme devices will be having their own custom version of ColorOS), and released an official ROM for the OnePlus One. CopperheadOS CopperheadOS, a security hardened version of Android EMUI Huawei EMUI is a front-end touch interface developed by Huawei Technologies Co. Ltd. and its sub-brand Honor which is based on Google's Android Open Source Project (AOSP). EMUI is preinstalled on most Huawei and Honor devices. While it was based on open source Android operating system, it consists of closed source and proprietary software. /e/ /e/ is an operating system forked from the source code of LineageOS (based on Android). /e/ targets Android smart phone devices, and uses MicroG as a replacement for Google Play Services. Current /e/ OS version list /e/ OS beta v0.1 (based on Android "Nougat" 7.1.x) /e/ OS beta v0.2 (based on Android "Oreo" 8.x.x) Fire OS Amazon Fire OS is an Android-based mobile operating system produced by Amazon for its Fire range of tablets, Echo and Echo Dot, and other content delivery devices like Fire TV (Previously for their Fire Phone). It is forked from Android. Fire OS primarily centers on content consumption, with a customized user interface and heavy ties to content available from Amazon's own storefronts and services. Current Fire OS version list Fire OS 1.x Fire OS 2.x Fire OS 3.x Fire OS 4.x Fire OS 5.x Fire OS 6.x Fire OS 7.x Flyme OS Flyme OS is an operating system developed by Meizu Technology Co., Ltd., an open source OS based on Google Android Open Source Project (AOSP). Flyme OS is mainly installed on Meizu Smartphones such as the MX's series; however, it also has official ROM support for a few Android devices. Current Flyme OS version list Flyme OS 1.x.x (based on Android "Ice Cream Sandwich" 4.0.3, initial release) Flyme OS 2.x.x (based on Android "Jelly Bean" 4.1.x – 4.2.x) Flyme OS 3.x.x (based on Android "Jelly Bean" 4.3.x) Flyme OS 4.x.x (based on Android "KitKat" 4.4.x) Flyme OS 5.x.x (based on Android "Lollipop" 5.0.x – 5.1.x) Flyme OS 6.x.x (based on Android "Nougat" 7.x, "Marshmallow" 6.0.x and Android "Lollipop" 5.0.x – 5.1.x for old devices) Flyme OS 7.x.x (based on Android "Pie" 9.0, "Oreo" 8.x and Android "Nougat" 7.x) Flyme OS 8.x.x (based on Android 10, "Pie" 9.0, "Oreo" 8.x and Android "Nougat" 7.x) GrapheneOS GrapheneOS, formerly named Android Hardening, is a variant of Android that runs on Pixel 2 or Pixel 3 hardware, is mainly developed by Daniel Micay , and aims to focus on security and privacy. HTC Sense HTC Sense is a software suite developed by HTC, used primarily on the company's Android-based devices. Serving as a successor to HTC's TouchFLO 3D software for Windows Mobile, Sense modifies many aspects of the Android user experience, incorporating added features (such as an altered home screen and keyboard), widgets, HTC-developed applications, and redesigned applications. The first device with Sense, the HTC Hero, was released in 2009. HTC Sense 1.x (based on Android "Eclair" 2.0/2.1, initial release) HTC Sense 2.x (based on Android "Eclair", "Froyo" and "Gingerbread" 2.0/2.1, 2.2.x and 2.3.x, redesigned UI) HTC Sense 3.x (based on Android "Gingerbread" 2.3.x, redesigned UI) HTC Sense 4.x (based on Android "Ice Cream Sandwich" and "Jelly Bean" 4.0.x and 4.1.x, redesigned UI) HTC Sense 5.x (based on Android "Jelly Bean" 4.1.x – 4.3.x, redesigned UI) HTC Sense 6.x (based on Android "KitKat" 4.4.x, redesigned UI) HTC Sense 7.x (based on Android "Lollipop" 5.0.x, redesigned UI) HTC Sense 8.x (based on Android "Marshmallow" 6.0.x, redesigned UI) HTC Sense 9.x (based on Android "Nougat" 7.x, redesigned UI) HTC Sense 10.x (based on Android "Oreo" 8.x and "Pie" 9.0, redesigned UI) iQOO UI iQOO UI is a customer user interface that is based on Vivo Funtouch OS, which itself is based on the Android Open Source Project (AOSP). The overall UI mostly resemble its predecessor, however with their own customized UI on top of the Funtouch OS. Current iQOO UI version list iQOO UI 1.x - Based on Funtouch OS Indus OS Indus OS is a custom mobile operating system based on the Android Open Source Project (AOSP). It is developed by the Indus OS team based in India. No longer valid as of 2018Indus OS is available on Micromax, Intex, Karbonn, and other Indian smartphone brands. Current Indus OS version list Firstouch OS (based on Android "Lollipop" 5.0) Indus OS 2.0 (based on Android "Marshmallow" 6.0) Indus OS 3.0 (based on Android "Nougat" 7.0.1) LG UX LG UX (formerly named Optimus UI) is a front-end touch interface developed by LG Electronics with partners, featuring a full touch user interface. It is sometimes incorrectly identified as an operating system. LG UX is used internally by LG for sophisticated feature phones and tablet computers, and is not available for licensing by external parties. Optimus UI 2 which based on Android 4.1.2 has been released on the Optimus K II and the Optimus Neo 3. It features a more refined user interface compared to the prior version based on Android 4.1.1, would include together which new functionality such as voice shutter and quick memo. Current LG UX version list Optimus UI 1.x – based on Android "Gingerbread" 2.3.x, initial release Optimus UI 2.x – based on Android "Ice Cream Sandwich" and "Jelly Bean" 4.0.x and 4.1.x – 4.3.x, redesigned UI LG UX 3.x – based on Android "KitKat" and "Lollipop" 4.4.x and 5.0.x, redesigned UI LG UX 4.x – based on Android "Lollipop" and "Marshmallow" 5.1.x and 6.0.x, redesigned UI LG UX 5.x – based on Android "Marshmallow" and "Nougat" 6.0.x and 7.0.x, redesigned UI LG UX 6.x – based on Android "Nougat" 7.0.x, redesigned UI LG UX 6.x+ – based on Android "Oreo" 8.0.x, redesigned UI LG UX 7.x – based on Android "Oreo" 8.x, redesigned UI LG UX 7.x+ – based on Android "Oreo" 8.x., redesigned UI LG UX 8.x – based on Android "Pie" 9.0, redesigned UI LG UX 9.x – based on Android 10 redesigned UI LineageOS Lineage Android Distribution is a custom mobile operating system based on the Android Open Source Project (AOSP). It serves as the successor to the highly popular custom ROM, CyanogenMod, from which it was forked in December 2016 when Cyanogen Inc. announced it was discontinuing development and shut down the infrastructure behind the project. Since Cyanogen Inc. retained the rights to the Cyanogen name, the project rebranded its fork as LineageOS. Similar to CyanogenMod, it does not include any proprietary apps unless the user installs them. It allows Android users who can no longer obtain update support from their manufacturer to continue updating their OS version to the latest one based on official release from Google AOSP and heavy theme customization. MiFavor MiFavor, was the custom Android UI that was developed by ZTE for their smartphone that is running Android platform. Similar to most of the other Android UI, MiFavor replace most of the stock apps with ZTE owns apps, however the all UX still closely similar to the stock Android. Current MiFavor version list MiFavor 1.x – based on Android "KitKat" 4.4.x, initial release MiFavor 2.x – based on Android "Lollipop" 5.0.x – 5.1.x, redesigned UI MiFavor 3.x – based on Android "Marshmallow" 6.x, redesigned UI MiFavor 4.x – based on Android "Nougat" 7.x, redesigned UI MiFavor 5.x – based on Android "Oreo" 8.x, redesigned UI MiFavor 9.x – based on Android "Pie" 9.0, redesigned UI MiFavor 10.x – based on Android 10, redesigned UI MIUI Mi User Interface (MIUI), developed by the Chinese electronic company Xiaomi Inc., is a mobile operating system based on the Android Open Source Project (AOSP). MIUI is mostly found in Xiaomi smartphones such as the Mi and Redmi Series; however, it also has official ROM support for few Android devices. Although MIUI is based on AOSP, which is open source, it consists of closed source and proprietary software of its own. One UI One UI (formerly called TouchWiz and Samsung Experience) is a front-end touch interface developed by Samsung Electronics In 2008 with partners, featuring a full touch user interface. It is sometimes incorrectly identified as an independent operating system. Samsung Experience is used internally by Samsung for smartphones, feature phones and tablet computers, and is not available for licensing by external parties as it is closed source and proprietary. The Android version of Samsung Experience also comes with Samsung-made apps preloaded (except starting with the Galaxy S6 which have removed all Samsung pre-loaded apps installed, leaving one with Samsung Galaxy Store (formerly Galaxy Apps), to save storage space and initially due to the removal of MicroSD). With the release of Samsung Galaxy S8 and S8+, Samsung Experience 8.1 was preinstall on it with introducing new function known as Samsung DeX. Similar to the concept of Microsoft Continuum, Samsung DeX allowed high end Galaxy devices such as S8/S8+ or Note 8 to connect into a docking station, which extends the functionality to allow desktop-like functionality by connecting a keyboard, mouse, and monitor. Samsung also announced "Linux on Galaxy", which allows to use the standard Linux distribution on the DeX platform. Previous Samsung Android UI version list TouchWiz 3.x (based on Android 2.1 "Éclair" and Android 2.2 "Froyo") (Initial release for Android UI) TouchWiz 4.x (based on Android 2.3 "Gingerbread" and Android 3.0 "Honeycomb") (Minor UI update) TouchWiz Nature UX (based on Android 4.0 "Ice Cream Sandwich") (Minor UI update) TouchWiz Nature UX 2.x (based on Android 4.2 "Jellybean") (Minor UI update) TouchWiz Nature UX 3.x (based on Android 4.4 "KitKat") (Minor UI update) TouchWiz Nature UX 4.x (based on Android 5 "Lollipop") (Minor UI update) TouchWiz Nature UX 5.x (based on Android 5 "Lollipop") (Major UI update) TouchWiz Nature UX 6.x (based on Android 6 "Marshmallow") (Minor UI update) TouchWiz Grace UX (based on Android 6 "Marshmallow") (Major UI update) Samsung Experience 8.x (based on Android 7 "Nougat") (Initial release migrate from TouchWiz) Samsung Experience 9.x (based on Android 8 "Oreo") (Minor update) Samsung Experience 10.x (based on Android 9 "Pie) (Minor and Last update before redesign One UI) Current One UI version list One UI 1.x (based on Android 9 "Pie") (Initial release) One UI 2.x (based on Android 10) (Minor UI update) One UI 3.x (based on Android 11) (Minor UI update) One UI 4.x (based on Android 12) (Upcoming update) OxygenOS OxygenOS is based on the open source Android Open Source Project (AOSP) and is developed by OnePlus to replace Cyanogen OS on OnePlus devices such as the OnePlus One, and it is preinstalled on the OnePlus 2, OnePlus X, OnePlus 3, OnePlus 3T, OnePlus 5, OnePlus 5T and OnePlus 6. As stated by Oneplus, OxygenOS is focused on stabilizing and maintaining of stock like those found on Nexus devices. It consists of mainly Google apps and minor UI customization to maintain the sleekness of pure Android. Current OxygenOS version list Oxygen OS 1.0.x (based on Android 5.0.x "Lollipop") (initial release) Oxygen OS 2.0.x (based on Android 5.1.x "Lollipop") (overall maintenance update) Oxygen OS 3.0.x (based on Android 6.0 "Marshmallow") (major Android update) Oxygen OS 3.1.x (based on Android 6.0.1 "Marshmallow") (minor maintenance update) Oxygen OS 3.2.x (based on Android 6.0.1 "Marshmallow") (major Android update) Oxygen OS 4.x.x (based on Android 7.x "Nougat") (major Android update) Oxygen OS 5.x.x (based on Android 8.x "Oreo") (major Android update) Oxygen OS 9.x.x (based on Android 9.0 "Pie") (major Android update) Oxygen OS 10.x.x (based on Android 10.0 "10") (major Android update) Oxygen OS 11.x.x (based on Android 11.0 "11") (major Android update) Oxygen OS 12.x.x (based on Android 12.0 "12") (major Android update) Pixel UI (Pixel Launcher) Google Pixel UI or Pixel Launcher is developed by Google that is based on open source Android. Unlike the Nexus phones, where Google shipped with the "stock" Android, the UI that came with the first generation Pixel phones were slightly modified as compared to the "stock" Android. As part of the Google Pixel software, the Pixel UI and its home launcher are closed source and proprietary, thus it is only available on the Pixel family devices. (However, third party mods allow non Pixel smartphones to install Pixel Launcher with Google Now feed integration). Current Google Pixel Launcher version list Pixel Launcher – "7.1.1" (based on Android 7.x "Nougat") (Initial release) Pixel Launcher – "8.1.0" (based on Android 8.x "Oreo") (Minor UI update) Pixel Launcher – "9.0" (based on Android 9.0 "Pie") (Minor UI update) Pixel Launcher – "10.0" (based on Android 10.0 "10") (Moderate UI update that support themes) Pixel Launcher – "11.0" (based on Android 11.0 "11") (Minor UI update) Pixel Launcher - "12.0" (based on Android 12.0 "12") (Major UI update) realme UI realme UI is a mobile operating system developed by Realme which is based on OPPO ColorOS, which itself is based on the Android Open Source Project (AOSP). The overall UI mostly resemble its predecessor, however with their own customized UI and element on top of the ColorOS to match their target audience. Current realme UI version list realme UI 1.0 - Based on ColorOS 7.0 - Android 10 - Initial Release realme UI 2.0 - Based on ColorOS 11.0 - Android 11 realme UI 3.0 - Based on ColorOS 12.0 - Android 12 Replicant OS Replicant is a custom mobile operating system based on the Android with all proprietary drivers and bloat closed source software removed. TCL UI TCL UI is a custom user interface that is developed by TCL Technology for their in house smartphone series, the OS is based on the Android Open Source Project (AOSP). Current TCL UI version list TCL UI 1.x - Based on Android 9 "Pie" and Android 10 - Initial Release Xperia UI Sony Xperia UI (formerly known as Sony Ericsson Timescape UI) was the front-end UI that developed by Sony Mobile (formerly Sony Ericsson) In 2010 for their Sony Xperia series that is running Android platform. Sony Xperia UI mostly consists of Sony own's application such as Sony Music (formerly known as Walkman Music player), Albums and Video Player. During its time as Timescape UI, the UI was different than the standard Android UI, instead of traditional apps dock on the bottom part, it was located at the four corner of the home screen, while the middle of the screen consist of the widget. However the recent development of UI are closely resemble to those of Stock Android. Current Xperia UI version list: Timescape version 1 – based on Android "Eclair" 2.0/2.1, initial release Timescape version 2 – based on Android "Gingerbread" 2.3.x, redesigned UI Xperia UI version 3 – based on Android "Gingerbread" and "Ice Cream Sandwich" 2.3.x and 4.0.x, redesigned UI Xperia UI version 4 – based on Android "Jelly Bean" 4.2.x – 4.3.x, redesigned UI Xperia UI version 5 – based on Android "KitKat" 4.4.x, redesigned UI Xperia UI version 6 – based on Android "Lollipop" 5.0.x – 5.1.x, redesigned UI Xperia UI version 7 – based on Android "Marshmallow" 6.0.x, redesigned UI Xperia UI version 8 – based on Android "Nougat" 7.x, redesigned UI Xperia UI version 9 – based on Android "Oreo" 8.x, redesigned UI ZenUI ZenUI is a front-end touch interface developed by ASUS with partners, featuring a full touch user interface. ZenUI is used by Asus for its Android phones and tablet computers, and is not available for licensing by external parties. ZenUI also comes preloaded with Asus-made apps like ZenLink (PC Link, Share Link, Party Link & Remote Link). Current ZenUI version list: ZenUI 1.0 – based on Android "Jelly Bean" and "KitKat" 4.3.x and 4.4.x, initial release ZenUI 2.0 – based on Android "Lollipop" 5.0.x – 5.1.x, redesigned UI ZenUI 3.0 – based on Android "Marshmallow" 6.0.x, redesigned UI ZenUI 4.0 – based on Android "Nougat" 7.x, redesigned UI ZenUI 5.0 – based on Android "Oreo" 8.x, redesigned UI ZenUI 6.0 – based on Android "Pie" 9.0, redesigned UI ZenUI 7.0 – based on Android 10, redesigned UI ZenUI 8.0 – based on Android 11, redesigned UI ZUI ZUI is a custom operating that is original develop by Lenovo subsidiary ZUK Mobile for their smartphones, however after the shutting down of ZUK Mobile, Lenovo had taken over as the main developer to continue developing the ZUI. The operating system is based on the Android Open Source Project (AOSP). ZUI 1.x - Initial Release ZUI 2.x ZUI 3.x ZUI 4.x ZUI 4.x ZUI 10.x (Based on Android 9 "Pie") ZUI 11.x (Based on Android 9 "Pie" and Android 10) Wear OS Wear OS (also known simply as Wear and formerly Android Wear) is a version of Google's Android operating system designed for smartwatches and other wearables. By pairing with mobile phones running Android version 6.0 or newer, or iOS version 10.0 or newer with limited support from Google's pairing application, Wear OS integrates Google Assistant technology and mobile notifications into a smartwatch form factor. In May 2021 at Google I/O, Google announced a major update to the platform, internally known as Wear OS 3.0. It incorporates a new visual design inspired by Android 12, and Fitbit exercise tracking features. Google also announced a partnership with Samsung Electronics, who is collaborating with Google to unify its Tizen-based smartwatch platform with Wear OS, and has committed to using Wear OS on its future smartwatch products. The underlying codebase was also upgraded to Android 11. Wear OS 3.0 will be available to Wear OS devices running Qualcomm Snapdragon Wear 4100 system on chip, and will be an opt-in upgrade requiring a factory reset to install. Current Wear OS version list: Android Wear 4.4w (Based on Android 4.4 "KitKat") - (Initially release) Android Wear 1.0 - 1.3 (Based on Android 5.0 "Lollipop) - (Minor update) Android Wear 1.4 (Based on Android 6.0 "Marshmellow) - (Minor update) Android Wear 2.0 - 2.6 (7.1.1W2) (Based on Android 7.1 "Nougat") - (Minor update) Android Wear 2.6 (7.1.1W3, 8.0.0 W1) - 2.9 (7.1.1W6, 8.0.0W4) (Baded on Android 8.0 "Oreo") - (Minor update) Wear OS 1.0 (Based on Android 8.0 "Oreo") - (Renamed and Minor update) Wear OS 2.0 (Based on Android 8.0 "Oreo") - (Minor update) Wear OS 2.2 (Based on Android 9.0 "Pie") - (Minor update) Wear OS 3.0 (Based on Android 11) - (Major UI and system update) One UI Watch One UI Watch is the user interface Samsung developed for their Wear OS based smartwatch, officially announced after both Google and Samsung confirm both company is going to unify their wearable operating system (Google Wear OS 2.0 and Samsung Tizen) into Wear OS 3.0. Current One UI Watch version list: One UI Watch 3.0 (Based on Wear OS 3.0 - Android 11)(Initially release) Chrome OS Chrome OS is an operating system designed by Google that is based on the Linux kernel and uses the Google Chrome web browser as its principal user interface. As a result, Chrome OS primarily supports web applications. Google announced the project in July 2009, conceiving it as an operating system in which both applications and user data reside in the cloud: hence Chrome OS primarily runs web applications. Due to increase of popularity with 2-in-1 PCs, most recent Chromebooks are introduced with touch screen capability, with Android applications starting to become available for the operating system in 2014. And in 2016, access to Android apps in the entire Google Play Store was introduced on supported Chrome OS devices. With the support of Android applications, there are Chromebook devices that are positioned as tablet based instead of notebooks. Chrome OS is only available pre-installed on hardware from Google manufacturing partners. An open source equivalent, Chromium OS, can be compiled from downloaded source code. Early on, Google provided design goals for Chrome OS, but has not otherwise released a technical description. Sailfish OS Sailfish OS is from Jolla. It is open source with GNU General Public License (GPL) for middleware stack core which comes from MER. Sailfish due to Jolla's business model and due to alliances with various partners and due to intentional design of OS internals, is capable to adopt in several layers third-party software including Jolla software e.g. Jolla's UI is proprietary software (closed source), so such components can be proprietary with many different kinds of licences. However, user can replace them with open source components like e.g. NEMO UI instead Jolla's UI. After Nokia abandoned in 2011 the MeeGo project, most of the MeeGo team left Nokia, and established Jolla as a company to use MeeGo and Mer business opportunities. The MER standard allows it to be launched on any hardware with kernel compatible with MER. In 2012, Linux Sailfish OS based on MeeGo and using middleware of MER core stack distribution was launched for public use. The first device, the Jolla smartphone, was unveiled on May 20, 2013. In 2015, Jolla Tablet was launched and the BRICS countries declared it an officially supported OS there. Jolla started licensing Sailfish OS 2.0 for third parties. Some devices sold are updateable to Sailfish 2.0 with no limits. Nemo Mobile is a community-driven OS, similar to Sailfish but attempting to replace its proprietary components, such as the user interface. Each Sailfish OS version release is named after a Finnish lake: Tizen Tizen (based on the Linux kernel) is a mobile operating system hosted by Linux Foundation, together with support from the Tizen Association, guided by a Technical Steering Group composed of Intel and Samsung. Tizen is an operating system for devices including smartphones, tablets, In-Vehicle Infotainment (IVI) devices, however currently it mainly focus on wearable and smart TVs. It is an open source system (however the SDK was closed source and proprietary) that aims to offer a consistent user experience across devices. Tizen's main components are the Linux kernel and the WebKit runtime. According to Intel, Tizen "combines the best of LiMo and MeeGo." HTML5 apps are emphasized, with MeeGo encouraging its members to transition to Tizen, stating that the "future belongs to HTML5-based applications, outside of a relatively small percentage of apps, and we are firmly convinced that our investment needs to shift toward HTML5." Tizen will be targeted at a variety of platforms such as handsets, touch pc, smart TVs and in-vehicle entertainment. On May 17, 2013, Tizen released version 2.1, code-named Nectarine. While Tizen itself was open source, most of the UX and UI layer that developed by Samsung was mainly closed source and proprietary, such as the TouchWiz UI on the Samsung Z's series smartphone and One UI for their Galaxy Watch wearable lines. KaiOS KaiOS is from Kai. It is based on Firefox OS/Boot to Gecko. Unlike most mobile operating systems which focus on smartphones, KaiOS was developed mainly for feature phones, giving these access to more advanced technologies usually found on smartphones, such as app stores and Wi-Fi/4G capabilities. It is a mix of closed-source and open-source components. FirefoxOS/B2G was released under the permissive MPL 2.0. It does not redistribute itself under the same license, so KaiOS is now presumably proprietary (but still mostly open-source, publishing its source code). KaiOS is not entirely proprietary, as it uses the copyleft GPL Linux kernel also used in Android. Fully open-source, entirely permissive licenses Fuchsia Fuchsia is a capability-based, real-time operating system (RTOS) currently being developed by Google. It was first discovered as a mysterious code post on GitHub in August 2016, without any official announcement. In contrast to prior Google-developed operating systems such as Chrome OS and Android, which are based on Linux kernels, Fuchsia is based on a new microkernel called "Zircon", derived from "Little Kernel", a small operating system intended for embedded systems. This allows it to remove Linux and the copyleft GPL underwhich the Linux kernel is licensed; Fuchsia is licensed under the permissive BSD 3-clause, Apache 2.0, and MIT licenses. Upon inspection, media outlets noted that the code post on GitHub suggested Fuchsia's capability to run on universal devices, from embedded systems to smartphones, tablets and personal computers. In May 2017, Fuchsia was updated with a user interface, along with a developer writing that the project was not a for experimental, prompting media speculation about Google's intentions with the operating system, including the possibility of it replacing Android. LiteOS LiteOS is a lightweight open source real-time operating system which is part of Huawei's "1+2+1" Internet of Things solution, which is similar to Google Android Things and Samsung Tizen. It is released under the permissive BSD 3-clause license. Huawei LiteOS features lightweight, low-power, fast-response, multi-sensor collaboration, multi-protocol interconnect connectivity, enabling IoT terminals to quickly access the network. Huawei LiteOS will make intelligent hardware development easier. Thereby accelerating the realization of the interconnection of all things. Currently LiteOS are introduce to the consumer market with the Huawei Watch GT series and their sub-brand Honor Magic Watch series. Fully open-source, mixed copyleft and permissive licenses PureOS PureOS is a Debian GNU/Linux derivative using only free software meeting the Debian Free Software Guidelines, mainly the copyleft GPL. PureOS is endorsed by Free Software Foundation as one of the freedom-respecting operating systems. It is developed by Purism, and was already in use on Purism's laptops before it was used on the Librem 5 smartphone. Purism, in partnership with GNOME and KDE, aims to separate the CPU from the baseband processor and include hardware kill switches for the phone's Wi-Fi, Bluetooth, camera, microphone and baseband processor, and provide both GNOME and KDE Plasma Mobile as options for the desktop environment. Ubuntu Touch Ubuntu Touch is an open-source (GPL) mobile version of the Ubuntu operating system originally developed in 2013 by Canonical Ltd. and continued by the non-profit UBports Foundation in 2017. Ubuntu Touch can run on a pure GNU/Linux base on phones with the required drivers, such as the Librem 5 and the PinePhone. To enable hardware that was originally shipped with Android, Ubuntu Touch makes use of the Android Linux kernel, using Android drivers and services via an LXC container, but does not use any of the Java-like code of Android. As of February 2022, Ubuntu Touch is available on 78 different phones and tablets. The UBports Installer serves as an easy-to-use tool to allow inexperienced users to install the operating system on third-party devices without damaging their hardware. Plasma mobile Plasma Mobile is a Plasma variant for smartphones. Plasma Mobile runs on Wayland and it is compatible with Ubuntu Touch applications, PureOS applications, and eventually Android applications via KDE's Shashlik project also sponsored by Blue Systems, or Anbox. It is under the copyleft GPLv2 license. The Necuno phone uses Plasma Mobile. It is which is entirely open-source and thus does not have a cellular modem, so it must make calls by VOIP, like a pocket computer. PostmarketOS PostmarketOS is based on the Alpine Linux Linux distribution. It is intended to run on older phone hardware. it is in alpha. LuneOS LuneOS is a modern reimplementation of the Palm/HP webOS interface. Closed source iOS iOS (formerly named iPhone OS) was created by Apple Inc. It has the second largest installed base worldwide on smartphones, but the largest profits, due to aggressive price competition between Android-based manufacturers. It is closed source and proprietary, and is built on the open source Darwin operating system. The iPhone, iPod Touch, iPad and second or third-generation Apple TV all use iOS, which is derived from macOS. Native third-party applications were not officially supported until the release of iPhone OS 2.0 on July 11, 2008. Before this, "jailbreaking" allowed third-party applications to be installed. In recent years, the jailbreaking scene has changed drastically due to Apple's continued efforts to secure their operating system and prevent unauthorized modifications. Currently, jailbreaks of recent iterations of iOS are only semi-untethered, which requires a device to be re-jailbroken at every boot, and exploits for jailbreaks are becoming increasingly hard to find and use. Currently all iOS devices are developed by Apple and manufactured by Foxconn or another of Apple's partners. iPadOS iPadOS is a tablet operating system created and developed by Apple Inc. specifically for their iPad line of tablet computers. It was announced at the company's 2019 Worldwide Developers Conference (WWDC), as a derivation from iOS but with a greater emphasis put on multitasking. It was released on September 24, 2019. watchOS watchOS is the operating system of the Apple Watch, developed by Apple Inc. It is based on the iOS operating system and has many similar features. It was released on April 24, 2015, along with the Apple Watch, the only device that runs watchOS. It is currently the most widely used wearable operating system. Its features focus on convenience, such as being able to place phone calls and send texts, and health, such as fitness and heart rate tracking. The most current version of the watchOS operating system is watchOS 7. Kindle firmware Kindle firmware is mobile operating system specifically design for Amazon Amazon Kindle e-readers, it is based on custom Linux kernel however it is entirely closed source and proprietary, and only runs on Amazon Kindle line up manufactured under Amazon brand. Windows 10 Windows 10 (not to be confused with Windows 10 Mobile—see below) is a personal computer operating system developed and released by Microsoft as part of the Windows NT family of operating systems. It was released on July 29, 2015, and many editions and versions have been released since then. Just like its predecessors, it was designed to run across multiple Microsoft product such as PCs and Tablets. The Windows user interface was revised to handle transitions between a mouse-oriented interface and a touchscreen-optimized interface based on available input devices‍—‌particularly on 2-in-1 PCs. Windows 10 also introduces the universal apps, expanding on Metro-style apps, these apps can be designed to run across multiple Microsoft product families with nearly identical code‍—‌including PCs, tablets, smartphones, embedded systems, Xbox One, Surface Hub and Mixed Reality. Windows 11 Windows 11 is a major version of the Windows NT operating system developed by Microsoft that was announced on June 24, 2021, and is the successor to Windows 10, which was released n 2015. Windows 11 was released on October 5, 2021, as a free upgrade via Windows Update for eligible devices running Windows 10. Microsoft promoted that Windows 11 would have improved performance and ease of use over Windows 10; it features major changes to the Windows shell influenced by the canceled Windows 10X, including a redesigned Start menu, the replacement of its "live tiles" with a separate "Widgets" panel on the taskbar, the ability to create tiled sets of windows that can be minimized and restored from the taskbar as a group, and new gaming technologies inherited from Xbox Series X and Series S such as Auto HDR and DirectStorage on compatible hardware. Internet Explorer is fully replaced by the Blink layout engine-based Microsoft Edge, while Microsoft Teams is integrated into the Windows shell. Microsoft also announced plans to offer support for Android apps to run on Windows 11, with support for Amazon Appstore and manually-installed packages. Similar to Windows 10, it was designed to run across multiple Microsoft product such as PCs and Tablets. The Windows user interface was further revised to combine the UI element of both mouse-oriented interface and a touchscreen-optimized interface based into a hybrid UI that combined touch and traditional desktop UI. Minor proprietary operating system Other than the major mobile operating system from the major tech company, some company such as Huami(Amazfit), Huawei, realme, TCL and Xiaomi has their own proprietary RTOS that develop specifically for their own smartband and smartwatch that is design to be power efficient and low battery consumption that is neither based on Android nor Linux Kernel. Proprietary Amazfit OS Operating System that is primarily design for their Bip series, however Huami is currently developing the operating system to run on other company smartwatch as well. (Not to be confused with the Android-based Amazfit OS as both of them sharing the name yet both are based on different operating system, for their Android based Amazfit OS, kindly refer to the Android section) Huawei/Honor Band Operating System Huawei Band Operating system is an operating system specifically designed and developed by Huawei for their fitness tracker, including smartband series from Honor. (Not to be confused with another RTOS (LiteOS) which was also developed by Huawei.) Lenovo RTOS Proprietary OS develop by Lenovo for their fitness tracker and smartwatch. realme Wearable Operating System A proprietary operating system design to run on realme smartband and smartwatch. TCL Wearable Real Time Operating System A proprietary RTOS powering TCL and Alcatel brand smartband and smartwatch. Xiaomi Mi Band Operating System Proprietary RTOS that is develop by Huami for Xiaomi Mi Band series. (Not to be confused with Xiaomi MIUI for smartwatch which is based on Wear OS) Under maintenance only BlackBerry 10 BlackBerry 10 (based on the QNX OS) is from BlackBerry. As a smartphone OS, it is closed source and proprietary, and only runs on phones and tablets manufactured by BlackBerry. One of the dominant platforms in the world in the late 2000s, its global market share was reduced significantly by the mid-2010s. In late 2016, BlackBerry announced that it will continue to support the OS, with a promise to release 10.3.3. Therefore, BlackBerry 10 would not receive any major updates as BlackBerry and its partners would focus more on their Android base development. Discontinued software platforms Open source CyanogenMod CyanogenMod was a custom mobile operating system based on the Android Open Source Project (AOSP). It was a custom ROM that was co-developed by the CyanogenMod community. The OS did not include any proprietary apps unless the user installed them. Due to its open source nature, CyanogenMod allowed Android users who could no longer obtain update support from their manufacturer to continue updating their OS version to the latest one based on official releases from Google AOSP and heavy theme customization. The last version of the OS was CyanogenMod 13 which was based on Android Asus On December 24, 2016, CyanogenMod announced on their blog that they would no longer be releasing any CyanogenMod updates. All development moved to LineageOS. Cyanogen OS Cyanogen OS was based on CyanogenMod and maintained by Cyanogen Inc; however, it included proprietary apps and it was only available for commercial uses. Firefox OS Firefox OS (formerly known as "Boot to Gecko" and shortly "B2G") is from Mozilla. It was an open source mobile operating system released under the Mozilla Public License built on the Android Linux kernel and used Android drivers, but did not use any Java-like code of Android. According to Ars Technica, "Mozilla says that B2G is motivated by a desire to demonstrate that the standards-based open Web has the potential to be a competitive alternative to the existing single-vendor application development stacks offered by the dominant mobile operating systems." In September 2016, Mozilla announced that work on Firefox OS has ceased, and all B2G-related code would be removed from mozilla-central. MeeGo/Maemo/Moblin MeeGo was from non-profit organization The Linux Foundation. It is open source and GPL. At the 2010 Mobile World Congress in Barcelona, Nokia and Intel both unveiled MeeGo, a mobile operating system that combined Moblin and Maemo to create an open-sourced experience for users across all devices. In 2011 Nokia announced that it would no longer pursue MeeGo in favor of Windows Phone. Nokia announced the Nokia N9 on June 21, 2011, at the Nokia Connection event in Singapore. LG announced its support for the platform. Maemo was a platform developed by Nokia for smartphones and Internet tablets. It is open source and GPL, based on Debian GNU/Linux and draws much of its graphical user interface (GUI), frameworks, and libraries from the GNOME project. It uses the Matchbox window manager and the GTK-based Hildon as its GUI and application framework. webOS webOS was developed by Palm. webOS is an open source mobile operating system running on the Linux kernel, initially developed by Palm, which launched with the Palm Pre. After being acquired by HP, two phones (the Veer and the Pre 3) and a tablet (the TouchPad) running webOS were introduced in 2011. On August 18, 2011, HP announced that webOS hardware would be discontinued, but would continue to support and update webOS software and develop the webOS ecosystem. HP released webOS as open source under the name Open webOS, and plans to update it with additional features. On February 25, 2013, HP announced the sale of webOS to LG Electronics, who used the operating system for its "smart" or Internet-connected TVs. However, HP retained patents underlying WebOS and cloud-based services such as the App Catalog. Closed source BlackBerry OS In 1999, Research In Motion released its first BlackBerry devices, providing secure real-time push-email communications on wireless devices. Services such as BlackBerry Messenger provide the integration of all communications into a single inbox. In September 2012, RIM announced that the 200 millionth BlackBerry smartphone was shipped. As of September 2014, there were around 46 million active BlackBerry service subscribers. In the early 2010s, RIM has undergone a platform transition, changing its company name to BlackBerry Limited and making new devices on a new platform named "BlackBerry 10". Symbian Symbian platform was developed by Nokia for some models of smartphones. It is proprietary software, it was however used by Ericsson (SonyEricsson), Sending and Benq. The operating system was discontinued in 2012, although a slimmed-down version for basic phones was still developed until July 2014. Microsoft officially shelved the platform in favor of Windows Phone after its acquisition of Nokia. Bada Bada platform (stylized as bada; Korean: 바다) was an operating system for mobile devices such as smartphones and tablet computers. It was developed by Samsung Electronics. Its name is derived from "바다 (bada)", meaning "ocean" or "sea" in Korean. It ranges from mid- to high-end smartphones. To foster adoption of Bada OS, since 2011 Samsung reportedly has considered releasing the source code under an open-source license, and expanding device support to include Smart TVs. Samsung announced in June 2012 intentions to merge Bada into the Tizen project, but would meanwhile use its own Bada operating system, in parallel with Google Android OS and Microsoft Windows Phone, for its smartphones. All Bada-powered devices are branded under the Wave name, but not all of Samsung's Android-powered devices are branded under the name Galaxy. On February 25, 2013, Samsung announced that it will stop developing Bada, moving development to Tizen instead. Bug reporting was finally terminated in April 2014. Palm OS Palm OS/Garnet OS was from Access Co. It is closed source and proprietary. webOS was introduced by Palm in January 2009, as the successor to Palm OS with Web 2.0 technologies, open architecture and multitasking abilities. Microsoft Windows Mobile Windows Mobile is a family of proprietary operating systems from Microsoft aimed at business and enterprise users, based on Windows CE and originally developed for Pocket PC (PDA) devices. In 2010 it was replaced with the consumer-focused Windows Phone. Versions of Windows Mobile came in multiple editions, like "Pocket PC Premium," "Pocket PC Professional," "Pocket PC Phone," and "Smartphone" (Windows Mobile 2003) or "Professional," "Standard," and "Classic" (Windows Mobile 6.0). Some editions were touchscreen-only and some were keyboard-only, although there were cases where device vendors managed to graft support for one onto an edition targeted at the other. Cellular phone features were also only supported by some editions. Microsoft started work on a version of Windows Mobile that would combine all features together, but it was aborted, and instead they focused on developing the non-backwards-compatible, touchscreen-only Windows Phone 7. Windows Phone Windows Phone is a proprietary mobile operating system developed by Microsoft for smartphones as the replacement successor to Windows Mobile and Zune. Windows Phone features a new touchscreen-oriented user interface derived from Metro design language. Windows Phone was replaced by Windows 10 Mobile in 2015. Windows 10 Mobile Windows 10 Mobile (formerly called Windows Phone) is from Microsoft. It is closed source and proprietary. Unveiled on February 15, 2010, Windows Phone includes a user interface inspired by Microsoft's Metro Design Language. It is integrated with Microsoft services such as OneDrive and Office, Xbox Music, Xbox Video, Xbox Live games and Bing, but also integrates with many other non-Microsoft services such as Facebook and Google accounts. Windows Phone devices were made primarily by Microsoft Mobile/Nokia, and also by HTC and Samsung. On January 21, 2015, Microsoft announced that the Windows Phone brand will be phased out and replaced with Windows 10 Mobile, bringing tighter integration and unification with its PC counterpart Windows 10, and provide a platform for smartphones and tablets with screen sizes under 8 inches. On October 8, 2017, Microsoft officially announced that they would no longer push any major updates to Windows 10 Mobile, instead it would put it in maintenance mode, where Microsoft would push bug fixes and general improvements only, therefore Windows 10 Mobile would not receive any new feature updates. On January 18, 2019, Microsoft announced that support for Windows 10 Mobile would end on December 10, 2019, with no further security updates released after then, and that Windows 10 Mobile users should migrate to iOS or Android phones. Current Windows 10 Mobile version list: Windows 10 Mobile – Version 1511 (November Update "Threshold") – major UI update Windows 10 Mobile – Version 1607 (Anniversary Update "Redstone 1") Windows 10 Mobile – Version 1703 (Creators Update "Redstone 2") Windows 10 Mobile – Version 1709 (Fall Creators Update) Market share Usage In 2006, Android and iOS did not exist and only 64 million smartphones were sold. In 2018 Q1, 383.5 million smartphones were sold and global market share was 85.9% for Android and 14.1% for iOS. Other OS smartphones were 0,131 million, counting the 0.03% of the total. According to StatCounter web use statistics (a proxy for all use), smartphones (alone without tablets) have majority use globally, with desktop computers used much less (and Android in particular more popular than Windows). Use varies however by continent with smartphones way more popular in the biggest continents, i.e. Asia, and the desktop still more popular in some, though not in North America. The desktop is still popular in many countries (while overall down to 44.9% in the first quarter of 2017), smartphones are more popular even in many developed countries (or about to be in more). A few countries on any continent are desktop-minority; European countries (and some in South America, and a few, e.g. Haiti, in North America; and most in Asia and Africa) are smartphone-majority, Poland and Turkey highest with 57.68% and 62.33%, respectively. In Ireland, smartphone use at 45.55% outnumbers desktop use and mobile as a whole gains majority when including the tablet share at 9.12%. Spain is also slightly desktop-minority. The range of measured mobile web use varies a lot by country, and a StatCounter press release recognizes "India amongst world leaders in use of mobile to surf the internet" (of the big countries) where the share is around (or over) 80% and desktop is at 19.56%, with Russia trailing with 17.8% mobile use (and desktop the rest). Smartphones (alone, without tablets), first gained majority in December 2016 (desktop-majority was lost the month before), and it wasn't a Christmas-time fluke, as while close to majority after smartphone majority happened again in March 2017. In the week from November 7–13, 2016, smartphones alone (without tablets) overtook desktop, for the first time (for a short period; non-full-month). Mobile-majority applies to countries such as Paraguay in South America, Poland in Europe and Turkey; and most of Asia and Africa. Some of the world is still desktop-majority, with e.g. in the United States at 54.89% (but no not on all days). However, in some territories of the United States, such as Puerto Rico, desktop is way under majority, with Windows under 30% overtaken by Android. On October 22, 2016 (and subsequent weekends), mobile showed majority. Since October 27, the desktop hasn't shown majority, not even on weekdays. And smartphones alone have showed majority since December 23 to the end of the year, with the share topping at 58.22% on Christmas Day. To the "mobile"-majority share then of smartphones, tablets could be added giving a 63.22% majority. While an unusually high top, a similarly high also happened on Monday April 17, 2017, with then only smartphones share slightly lower and tablet share slightly higher, with them combined at 62.88%. , the world has turned desktop-minority; at about 49% desktop use for the previous month, but mobile wasn't ranked higher, tablet share had to be added to it to exceed desktop share. By now, mobile (smartphones) have full majority, outnumbering desktop/laptop computers by a safe margin (and no longer counting tablets with desktops makes them most popular). By operating system Note: Windows includes all versions. BlackBerry includes all versions. Other includes all other smartphone OSes but not feature phone OSes. See also Comparison of mobile operating systems Usage share of operating systems Real-time operating system List of GPS software for mobile phones Mobile device Smartphone Tablet computer Information appliance List of open-source mobile phones Operating system Network operating system References External links Android Apple Operating systems Mobile phones Software wars

Operating System (OS)

Timeline of operating systems This article presents a timeline of events in the history of computer operating systems from 1951 to the current day. For a narrative explaining the overall developments, see the History of operating systems. 1950s 1951 LEO I 'Lyons Electronic Office' was the commercial development of EDSAC computing platform, supported by British firm J. Lyons and Co. 1955 MIT's Tape Director operating system made for UNIVAC 1103 1955 General Motors Operating System made for IBM 701 1956 GM-NAA I/O for IBM 704, based on General Motors Operating System 1957 Atlas Supervisor (Manchester University) (Atlas computer project start) BESYS (Bell Labs), for IBM 704, later IBM 7090 and IBM 7094 1958 University of Michigan Executive System (UMES), for IBM 704, 709, and 7090 1959 SHARE Operating System (SOS), based on GM-NAA I/O 1960s 1960 IBSYS (IBM for its 7090 and 7094) 1961 CTSS demonstration (MIT's Compatible Time-Sharing System for the IBM 7094) MCP (Burroughs Master Control Program) 1962 Atlas Supervisor (Manchester University) (Atlas computer commissioned) BBN Time-Sharing System GCOS (GE's General Comprehensive Operating System, originally GECOS, General Electric Comprehensive Operating Supervisor) 1963 AN/FSQ-32, another early time-sharing system begun CTSS becomes operational (MIT's Compatible Time-Sharing System for the IBM 7094) JOSS, an interactive time-shared system that did not distinguish between operating system and language Titan Supervisor, early time-sharing system begun 1964 KDF9 Timesharing Director (English Electric) – an early, fully hardware secured, fully pre-emptive process switching, multi-programming operating system for KDF9 (originally announced in 1960) Berkeley Timesharing System (for Scientific Data Systems' SDS 940) Dartmouth Time Sharing System (Dartmouth College's DTSS for GE computers) OS/360 (IBM's primary OS for its S/360 series) (announced) SCOPE (CDC 3000 series) PDP-6 Monitor (DEC) descendant renamed TOPS-10 in 1970 EXEC 8 (UNIVAC) 1965 THE multiprogramming system (Technische Hogeschool Eindhoven) development Multics (MIT, GE, Bell Labs for the GE-645) (announced) BOS/360 (IBM's Basic Operating System) TOS/360 (IBM's Tape Operating System) TSOS (later VMOS) (RCA) Pick operating system 1966 OS/360 (IBM's primary OS for its S/360 series) PCP and MFT (shipped) DOS/360 (IBM's Disk Operating System) MS/8 (Richard F. Lary's DEC PDP-8 system) GEORGE 1 & 2 for ICT 1900 series SODA for Elwro's Odra 1204 1967 CP-40, predecessor to CP-67 on modified IBM System/360 Model 40 CP-67 (IBM, also known as CP/CMS) Michigan Terminal System (MTS) (time-sharing system for the IBM S/360-67 and successors) ITS (MIT's Incompatible Timesharing System for the DEC PDP-6 and PDP-10) ORVYL (Stanford University's time-sharing system for the IBM S/360) TSS/360 (IBM's Time-sharing System for the S/360-67, never officially released, canceled in 1969 and again in 1971) OS/360 MVT WAITS (SAIL, Stanford Artificial Intelligence Laboratory, time-sharing system for DEC PDP-6 and PDP-10, later TOPS-10) 1968 Airline Control Program (ACP) (IBM) THE multiprogramming system (Eindhoven University of Technology) publication TSS/8 (DEC for the PDP-8) 1969 TENEX (Bolt, Beranek and Newman for DEC systems, later TOPS-20) Unics (later Unix) (AT&T, initially on DEC computers) RC 4000 Multiprogramming System (RC) Multics (MIT, GE, Bell Labs for the GE-645 and later the Honeywell 6180) (opened for paying customers in October) GEORGE 3 For ICL 1900 series 1970s 1970 DOS-11 (PDP-11) 1971 RSTS-11 2A-19 (First released version; PDP-11) OS/8 1972 Data General RDOS Edos Operating System/Virtual Storage 1 (OS/VS1) Operating System/Virtual Storage 2 R1 (OS/VS2 SVS) Virtual Machine Facility/370 (VM/370), sometimes known as VM/CMS Virtual Machine/Basic System Extensions Program Product (BSEPP or VM/SE) Virtual Machine/System Extensions Program Product (SEPP or VM/BSE) MUSIC/SP PRIMOS (written in FORTRAN IV, that didn't have pointers, while later versions, around version 18, written in a version of PL/I, called PL/P) 1973 Эльбрус-1 (Elbrus-1) – Soviet computer – created using high-level language uЭль-76 (AL-76/ALGOL 68) VME – implementation language S3 (ALGOL 68) RSX-11D RT-11 Alto OS 1974 CP/M DOS-11 V09-20C (Last stable release, June 1974) Sintran III MONECS Multi-Programming Executive (MPE) – Hewlett-Packard Hydra – capability-based, multiprocessing OS kernel Operating System/Virtual Storage 2 R2 (MVS) 1975 BS2000 V2.0 (First released version) Version 6 Unix 1976 Cambridge CAP computer – all operating system procedures written in ALGOL 68C, with some closely associated protected procedures in BCPL Cray Operating System FLEX TOPS-20 Tandem Nonstop OS v1 1977 1BSD KERNAL OASIS operating system TRSDOS Virtual Memory System (VMS) V1.0 (Initial commercial release, October 25) 1978 2BSD Apple DOS HDOS PTDOS TRIPOS UCSD p-System (First released version) Lisp machine (CADR) KVM/370 – security retro-fit of IBM VM/370 KSOS – secure OS design from Ford Aerospace MVS/System Extensions (MVS/SE) 1979 3BSD Atari DOS POS NLTSS UNIX/32V Version 7 Unix UCLA Secure UNIX – an early secure UNIX OS based on security kernel MVS/System Extensions R2 (MVS/SE2) MP/M 1980s 1980 86-DOS CTOS NewDos/80 OS-9 SOS MVS/System Product (MVS/SP) V1 Virtual Machine/System Product (VM/SP) Xenix AOS/VS (Data General) 1981 Acorn MOS Xinu first release Business Operating System Aegis SR1 (First Apollo/DOMAIN systems shipped on March 27) PC DOS Pilot (Xerox Star operating system) MS-DOS UTS iMAX – OS for Intel's iAPX 432 capability machine CP/M-86 1982 Commodore DOS LDOS (By Logical Systems, Inc. – for the Radio Shack TRS-80 Models I, II & III) QNX Sun UNIX (later SunOS) 0.7 Ultrix Stratus VOS Unix System III pSOS 1983 Lisa Office System 7/7 Coherent GNU (project start) Novell NetWare (S-Net) ProDOS SunOS 1.0 STOP – TCSEC A1-class, secure OS for SCOMP hardware LOCUS – UNIX compatible, high reliability, distributed OS DNIX MVS/System Product V2 (MVS/Extended Architecture, MVS/XA) 1984 AMSDOS Mac OS (System 1.0) MSX-DOS PC/IX Sinclair QDOS QNX UNICOS Venix 2.0 Virtual Machine/Extended Architecture Migration Assistance (VM/XA MA) 1985 Windows 1.0 AmigaOS Atari TOS DG/UX DOS Plus MIPS RISC/os Oberon – written in Oberon SunOS 2.0 Version 8 Unix Windows 1.01 Xenix 2.0 Virtual Machine/Extended Architecture System Facility (VM/XA SF) Graphics Environment Manager 1986 AIX 1.0 GS-OS Genera 7.0 HP-UX SunOS 3.0 GEOS Version 9 Unix GEMSOS – TCSEC A1-class, secure kernel for BLACKER VPN & GTNP Cronus distributed OS 1987 Topaz – semi-distributed OS for DEC Firefly workstation written in Modula-2+ and garbage collected Arthur (much improved version came in 1989 under the name RISC OS) IRIX (3.0 is first SGI version) MINIX 1.0 BS2000 V9.0 OS/2 (1.0) PC-MOS/386 Windows 2.0 1988 A/UX (Apple Computer) AOS/VS II (Data General) RISC iX KeyKOS – capability-based microkernel for IBM mainframes with automated persistence of app data LynxOS CP/M rebranded as DR-DOS Mac OS (System 6) MVS/System Product V3 (MVS/Enterprise Systems Architecture, MVS/ESA) OS/2 (1.1) OS/400 SpartaDOS X SunOS 4.0 TOPS-10 7.04 (Last stable release, July 1988) HeliOS 1.0 VAX VMM – TCSEC A1-class, VMM for VAX computers (limited use before cancellation) Flex machine – tagged, capability machine with OS and other software written in ALGOL 68RS Virtual Machine/Extended Architecture System Product (VM/XA SP) 1989 EPOC NeXTSTEP (1.0) OS/2 (1.2) RISC OS (First release was to be called Arthur 2, but was renamed to RISC OS 2, and was first sold as RISC OS 2.00 in April 1989) SCO UNIX (Release 3) TSX-32 Version 10 Unix Xenix 2.3.4 (Last stable release) Army Secure Operating System (ASOS) – TCSEC A1-class secure, real-time OS for Ada applications 1990s 1990 AmigaOS 2.0 BeOS (v1) DOS/V Genera 8.0 OS/2 1.3 OSF/1 AIX 3.0 MVS/ESA SP Version 4 Novell NetWare 3 Windows 3.0 LOCK – TCSEC A1-class secure system with kernel & hardware support for type enforcement Virtual Machine/Enterprise Systems Architecture (VM/XA ESA) PC/GEOS 1991 Linux 0.01-0.1 Mac OS (System 7) MINIX 1.5 PenPoint OS RISC OS 3 Trusted Xenix – rewritten & security enhanced Xenix evaluated at TCSEC B2-class Amoeba – microkernel-based, POSIX-compliant, distributed OS 1992 386BSD 0.1 BSD/386, by BSDi and later known as BSD/OS. AmigaOS 3.0 Amiga Unix 2.01 (Latest stable release) RSTS/E 10.1 (Last stable release, September 1992) SLS Solaris 2.0 (Successor to SunOS 4.x; based on SVR4 instead of BSD) OpenVMS V1.0 (First OpenVMS AXP (Alpha) specific version, November 1992) OS/2 2.0 (First i386 32-bit based version) Plan 9 First Edition (First public release was made available to universities) Windows 3.1 LGX 1993 FreeBSD NetBSD Newton OS Windows NT 3.1 (First Windows NT kernel public release) Open Genera 1.0 IBM 4690 Operating System Novell NetWare 4 OS/2 2.1 Slackware 1.0 Spring 1994 AIX 4.0, 4.1 IBM MVS/ESA SP Version 5 OS/2 3.0 RISC OS 3.5 NetBSD 1.0 (First multi-platform release, October 1994) SPIN – extensible OS written in Modula-3 Red Hat 1995 Digital UNIX (aka Tru64 UNIX) OpenBSD OS/390 Plan 9 Second Edition (Commercial second release version was made available to the general public.) Ultrix 4.5 (Last major release) Windows 95 1996 Mac OS 7.6 (First officially-named Mac OS) Windows NT 4.0 Windows CE 1.0 RISC OS 3.6 AIX 4.2 OS/2 4.0 Palm OS Debian 1.1 JN – microkernel OS for embedded, Java apps 1997 Inferno Mac OS 8 Windows CE 2.0 SkyOS MINIX 2.0 RISC OS 3.7 AIX 4.3 DR-WebSpyder 1.0 Nemesis 1998 Solaris 7 (first 64-bit Solaris release – names from this point drop "2.", otherwise would've been Solaris 2.7) Windows 98 RT-11 5.7 (Last stable release, October 1998) Novell NetWare 5 Junos DR-WebSpyder 2.0 1999 AROS (Boot for the first time in Stand Alone version) RISC OS 4 Mac OS 9 OS/2 4.5 Windows 98 (2nd edition) Inferno Second Edition (Last distribution (Release 2.3, ) from Lucent's Inferno Business Unit) 2000s 2010s 2020s See also Comparison of operating systems List of operating systems Comparison of real-time operating systems Timeline of DOS operating systems Timeline of Linux distributions (Diagram 1992–2010) References External links UNIX History – a timeline of UNIX 1969 and its descendants at present Concise Microsoft O.S. Timeline – a color-coded concise timeline for various Microsoft operating systems (1981–present) Full Form of Computer - Full Form and Working of Computers. Bitsavers – an effort to capture, salvage, and archive historical computer software and manuals from minicomputers and mainframes of the 1950s, 1960s, 1970s, and 1980s A brief history of operating systems Microsoft operating system time-line Timeline of operating systems Operating systems Operating systems Real-time operating systems Embedded operating systems

Operating System (OS)

Apple SOS The Sophisticated Operating System, or SOS , is the primary operating system of the Apple III computer. SOS was developed by Apple Computer and released in October 1980. In 1985, Steve Wozniak, while critical of the Apple III's hardware flaws, called SOS "the finest operating system on any microcomputer ever". Technical details SOS is a single-tasking single-user operating system. It makes the resources of the Apple III available in the form of a menu-driven utility program as well as a programming application programming interface (API). A single program is loaded at boot time, called the interpreter. Once loaded, the interpreter can then use the SOS API to make requests of the system. The SOS API is divided into four main areas: File Calls: Create, destroy, rename, open, close, read, write files; set, get prefix (current working directory); set, get file information; get volume information; set, set mark, EOF, and level of files Device Calls: Get status, device number, information of a device; send device control data Memory Calls: Request, find, change, release memory segment; get segment information; set segment number Utility Calls: Get, set fence (event threshold); get, set time; get analog (joystick) data; terminate. The Apple III System Utilities program shipped with each Apple III computer. It provides the user interface of the operating system itself, for system configuration and file management. The System Utilities program is menu-driven and performs tasks in three categories: Device-handling commands: copy, rename, format, verify volumes (drives); list devices; set time and date File-handling commands: list, copy, delete, rename files; create subdirectories; set file write protection; set prefix (current working directory) System Configuration Program (SCP): configure device drivers. SOS has two types of devices it communicates with via device drivers: character devices and block devices. Examples of SOS character devices are keyboards and serial ports. Disk drives are typical block devices. Block devices can read or write one or more 512-byte blocks at a time; character devices can read or write single characters at a time. Boot sequence When powered on, the Apple III runs through system diagnostics, then reads block number zero from the built-in diskette drive into memory and executes it. SOS-formatted diskettes place a loader program in block zero. That loader program searches for, loads, and executes a file named SOS.KERNEL, which is the kernel and API of the operating system. The kernel, in turn, searches for and loads a file named SOS.INTERP (the interpreter, or program, to run) and SOS.DRIVER, the set of device drivers to use. Once all files are loaded, control is passed to the SOS.INTERP program. Apple ProDOS uses the same file system as SOS. On a disk formatted by ProDOS, the ProDOS loader and SOS loader are written to blocks zero and one, respectively. The ProDOS loader includes code that can execute on an Apple III, and which will chainload the SOS loader from block one, so SOS and ProDOS can co-exist on the same volume. Some software, such as ADTPro, makes use of this to store Apple II and Apple III versions of a program on the same disk, which is then bootable on both systems. References External links Washington Apple Pi – Apple /// Resources The Apple /// FAQ File V5.1 – discusses Apple III and SOS history as well as basic information about the system apple3.org - Apple /// Articles, Public Domain Software Apple Inc. operating systems Disk operating systems Discontinued operating systems 1980 software

Operating System (OS)

ToaruOS ToaruOS (also known as ToAruOS or とあるOS; 'toaru' is Japanese roughly equivalent to 'a certain') is a hobby operating system and kernel developed largely independently (notably contrary to most modern OSes, which are based on existing source code) by K. Lange. Despite a 1.0 version being released, Lange has stated that it is still 'incomplete', and may not be 'suitable for any purpose you might have for an operating system'. It is released under the permissive UIUC License, and supports 64-bit computer hardware with SMP. Design and features ToaruOS is programmed in C, and uses the Cairo graphics library. It has support for GCC, Python, and Simple DirectMedia Layer as well as many open-source utilities – including Vim. A package manager and basic window switcher are also included. The kernel is a 'basic Unix-like environment'. It has a hybrid architecture, with internal and external device support being delegated to modules. Several filesystems are supported via this system, including ext2 and ISO 9660. Networking support is included, but is limited to simple IPv4 functionality. The userspace also has a window manager, Yutani (named after the Wayland-Yutani Corporation from the Alien franchise, and as a reference to the Wayland Display Server for Linux), with input support. It stores windows as shared memory regions with 32-bit colour, and uses pipes to communicate to other parts of the OS. Unusually, windows also support a rotation feature. History Development was started by creator K. Lange in December 2010; it initially was supported by the University of Illinois at Urbana–Champaign, but after the beginning of 2012, it largely shifted to being mostly done by Lange. Initially, it was based on tutorials for x86 kernels. The operating system was named after the A Certain Scientific Railgun series of manga, but Lange stated it also mirrors generic naming of other hobby OSes. A GUI was added with a window manager in 2012, this was replaced with a more advanced version in 2014. The initial official release, version 1.0, was released at the end of January. This marked the first stable release, but Lange stated it was still 'a work in development with so much work left to be done'. This was superseded by versions 1.0.1 and 1.0.2, which added audio improvements and fixed bugs. For April Fools' Day 2015, Lange released PonyOS, a version of ToaruOS themed after the animated series My Little Pony: Friendship Is Magic. See also TempleOS – another operating system developed largely from scratch Redox OS – another Unix-like independently developed OS References External links Official website toaruos on GitHub Free software operating systems X86 operating systems 2017 software Free software programmed in C Public-domain software with source code Lightweight Unix-like systems Hobbyist operating systems

Operating System (OS)

System 7 System 7, codenamed "Big Bang", and also known as Mac OS 7, is a graphical user interface-based operating system for Macintosh computers and is part of the classic Mac OS series of operating systems. It was introduced on May 13, 1991, by Apple Computer, Inc. It succeeded System 6, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997. Features added with the System 7 release included virtual memory, personal file sharing, QuickTime, QuickDraw 3D, and an improved user interface. With the release of version 7.6 in 1997, Apple officially renamed the operating system "Mac OS", a name which had first appeared on System 7.5.1's boot screen. System 7 was developed for Macs that used the Motorola 680x0 line of processors, but was ported to the PowerPC after Apple adopted the new processor in 1994 with the introduction of the Power Macintosh. Development The development of the Macintosh system software up to System 6 followed a fairly smooth progression with the addition of new features and relatively small changes and upgrades over time. Major additions were fairly limited. Some perspective on the scope of the changes can be seen by examining the official system documentation, Inside Macintosh. This initially shipped in three volumes, adding another to describe the changes introduced with the Mac Plus, and another for the Mac II and Mac SE. These limited changes meant that the original Macintosh system remained largely as it was when initially introduced. That is, the machine was geared towards a single user and task running on a floppy disk based machine of extremely limited RAM. However, many of the assumptions of this model were no longer appropriate. Most notable among these was the single-tasking model, the replacement of which had first been examined in 1986's "Switcher" and then replaced outright with MultiFinder in System 5. Running MultiFinder normally required a larger amount of RAM and a hard drive, but these became more common by the late 1980s. While additions had been relatively limited, so had fixes to some of the underlying oddities of the system architecture. For instance, to support a limited form of multitasking, the original Mac OS supported small co-resident programs known as desk accessories which had to be installed into the system using special tools. If the system were able to support multiple tasks, this one-off solution would no longer be needed — desk accessories could simply be small programs, placed anywhere. Yet, as MultiFinder was still optional, such a step had not been taken. Numerous examples of this sort of problem could be found throughout the system. Finally, the widespread adoption of hard drives and local area networks led to any number of new features being requested from users and developers. By the late 1980s, the list of new upgrades and suggested changes to the existing model was considerable. Pink and Blue In March 1988, shortly before the release of System 6, technical middle managers at Apple held an offsite meeting to plan the future course of Mac OS development. Ideas were written on index cards; features that seemed simple enough to implement in the short term (like adding color to the user interface) were written on blue cards, longer-term goals like true multitasking on pink cards, and "far out" ideas like an object-oriented file system on red cards. Development of the ideas contained on the blue and pink cards was to proceed in parallel, and at first the two projects were known simply as "blue" and "pink" (including Taligent). Apple intended to have the "blue" team (which came to call themselves the "Blue Meanies" after characters in Yellow Submarine) release an updated version of the existing Macintosh operating system in the 1990–1991 time-frame, and the "pink" team to release an entirely new OS around 1993. As Blue was aimed at relatively "simple" upgrades, the feature list reads to some degree as a sort of "System 6, corrected". In the underlying OS, a number of formerly optional components were made mandatory: 32-bit QuickDraw, supporting so-called "true color" imaging, was included as standard; it was previously available as a system extension. A new Sound Manager API, version 2.0, replaced the older ad hoc APIs. The new APIs featured significantly improved hardware abstraction, as well as higher-quality playback. Although technically not a new feature for System 7 (as these features were available for System 6.0.7), Sound Manager 2.0 was the first widespread implementation of this technology to make it to most Mac users. System 7 paved the way for a full 32-bit address space, from the previous 24-bit address space. This process involved making all of the routines in OS code use the full 32 bits of a pointer as an address—prior systems used the upper bits as flags. This change was known as being "32-bit clean". While System 7 itself was 32-bit clean, many existing machines and thousands of applications were not, so it was some time before the process was completed. To ease the transition, the "Memory" control panel contained a switch to disable this feature, allowing for compatibility with older applications but rendering any installed RAM over 8 MB unusable. System 7 made MultiFinder's cooperative multitasking mandatory. Furthermore, a number of oddities in the original System, typically included due to limited resources, were finally changed to use basic underlying OS features: Trash was now a normal directory, allowing items to be preserved between reboots and disk eject events instead of being purged. "System extensions" (small pieces of INIT code that extended the system's functionality) were relocated to their own subfolder (rather than in the root level of the System Folder itself as on earlier versions) and they could be installed or removed at the user's will simply by moving these "extensions" to or from the folder and then rebooting the computer. There was an auto-routing feature for extensions, control panels, fonts and Desk Accessories where they could simply be dropped onto the System folder. The system would detect the type and automatically place the moved files in the appropriate subdirectories. On reboot, the System would read the files and install the extensions, without the user having to do anything else. Additionally, all extensions and panels (see below) could be temporarily disabled by holding down the shift key when booting up. Later versions of System 7 offered a feature called "Extensions Manager" which simplified the process of enabling/disabling individual extensions. Extensions were often a source of instability and these changes made them more manageable and assisted trouble-shooting. Similarly, the Control Panel desk accessory became the Control Panels folder (found in the System Folder, and accessible to the user from an alias in the Apple menu). The control panels themselves became separate files, stored within this directory. Control panels are essentially system extensions with a user interface. The Apple menu (previously home only to desk accessories pulled from "DRVR" resources in the System file) now listed the contents of a folder ("Apple Menu Items"), including aliases (see below). Desk accessories had originally been intended to provide a form of multitasking and were no longer necessary now that real multitasking was always enabled. The desk-accessory technology was deprecated, with System 7 treating them largely the same as other applications. Desk accessories now ran in their own process rather than borrowing that of a host application. Under System 6, the Apple Menu contained both a list of desk accessories and a list of running programs under MultiFinder. In System 7 the list of active programs was relocated to its own Application Menu. The system also offered a wide variety of new features: Personal File Sharing. Along with various UI improvements for AppleTalk setup, System 7 also included a basic file sharing server allowing any machine to publish folders to the AppleTalk network. Aliases. An alias is a small file that represents another object in the file system. A typical alias is small, between 1 and 5 KB. Similar in concept to Unix symbolic links and Windows shortcuts, an alias acts as a redirect to any object in the file system, such as a document, an application, a folder, a hard disk, a network share or removable medium or a printer. When double-clicked, the computer will act the same way as if the original file had been double-clicked. Likewise, choosing an alias file from within an "Open" dialog box would open the original file. (Unlike the path-based approach of shortcuts and symbolic links, aliases also store a reference to the file's catalog entry, so they continue to work even if the file is moved or renamed. Aliases have features of both hard links and symbolic links found on Unix-based systems. All three are supported on macOS.) Drag and drop. Document icons could be dragged with the mouse and "dropped" onto application icons to open in the targeted application. Under System 6, one either double-clicked on a document icon to open its associated application, or one could open the desired application and use its Open dialog box. The development of the drag-and-drop paradigm led to a new concept for some applications—such as StuffIt Expander—whose main interactions were intended to be via drag and drop. System 7.5's Drag Manager expanded the concept system-wide to include multiple data types such as text or audio data. "Stationery", a template feature that allowed users to save often-used document styles in special format. "Stationery-aware" applications would create a new, untitled file containing the template data, while non-aware applications would immediately show a Save As dialog box asking the user for the file's name. Balloon Help, a widget-identification system similar to tooltips. AppleScript, a scripting language for automating tasks. While fairly complex for application programmers to implement support for, this feature was powerful and popular with users, and it remains supported as part of macOS. AppleEvents. Supporting AppleScript was a new interprocess communication model for "high-level" events to be sent into applications, along with support to allow this to take place over an AppleTalk network. Publish and Subscribe. This feature permitted data "published" by one application to be imported ("subscribed to") by another, and the data could be updated dynamically. Programmers complained that the API was unwieldy, and relatively few applications ended up adopting it. TrueType outline fonts. Up to this point, all fonts on the Macintosh were bitmapped, or a set of bitmapped screen fonts paired with outline PostScript printer fonts; TrueType for the first time offered a single font format that scaled to any size on screen and on paper. This technology was recognized as being so important that a TrueType extension for System 6 was also released, along with an updated Font/DA Mover capable of installing these new kinds of fonts into the System 6 System file. A newly colorized user interface. Although this feature made for a visually appealing interface, it was optional. On machines not capable of displaying color, or those with their display preferences set to monochrome, the interface defaulted back to the black-and-white look of previous versions. Only some widgets were colorized—scrollbars, for instance, had a new look, but buttons remained in black and white. System 7.1 marked the advent of System Enablers, small extensions that were loaded at startup to support Macintosh models introduced since the last OS revision. Under System 6, Apple had to introduce a number of minor revisions to the OS solely for use with new hardware. Apple introduced an unprecedented number of new Macintosh models during the System 7 era, leading to some confusion over which System Enabler went with which computer(s). Software System 7 was the first Apple operating system to be available on compact disc, although it shipped on a set of 15 floppy disks initially. Unlike earlier systems, System 7 did not come bundled with major software packages. Newly purchased Macintosh computers had System 7 installed and were often bundled with software such as HyperCard, At Ease and Mouse Practice. Later, the Macintosh Performa family added various software bundles including ClarisWorks, The New Grolier Multimedia Encyclopedia, Microsoft Bookshelf, Spectre VR and Power Pete. Since System 7 was introduced before the Internet came to popular attention, software such as MacTCP, FreePPP and Netscape were not included at first, but was later available on disk from Internet service providers and bundled with books such as Adam C. Engst's Internet Starter Kit for Macintosh. Power Macintosh machines also included NuCalc, a graphing calculator. System 7 also includes AppleTalk networking and file sharing software in the form of system extensions and control panels. The basic utilities installed by default with System 7 include TeachText (which was replaced by SimpleText in later versions) for basic text editing tasks and reading readme documents. Also available on the additional "Disk Tools" floppy disk are Disk First Aid for disk repair and Apple HD SC Setup for initializing and partitioning disks. Later versions of System 7, specifically System 7.5 and Mac OS 7.6, come with dedicated "Utilities" and "Apple Extras" folders including: AppleScript, Disk Copy, QuickDraw GX Extras and QuickTime Movie Player. More optional extras and utilities could be manually installed from the System CD. Transition to PowerPC System 7.1.2 is the first version of the Macintosh System Software to support Apple's new PowerPC-based computers. 68k applications which had not yet been updated to run natively on these systems were emulated transparently (without the user having to intervene) by a built-in 68k processor emulator. Fat binaries, which contained the code necessary to run natively on both PowerPC and 68k systems, became common during this time. This process was similar to the distribution of universal binaries during the Mac transition to Intel processors in 2006, as well as the Mac transition to Apple silicon beginning in 2020. System 7.1.2 is the only release of the Macintosh operating system that boots stating "Welcome to Power Macintosh." This despite the OS being designed to run on 68k Macintoshes that were upgraded to PowerPC, but without Power Macintosh branding. Subsequent System 7 release 7.1.2P reverted this. PC compatibility System 7.0 and 7.1 offered a utility called Apple File Exchange, which could access the contents of FAT- and Apple II-formatted floppy disks. System 7 Pro, System 7.5 and up shipped with PC Exchange, previously a separate product, which allowed the system to mount FAT-formatted floppy disks on the desktop in the same manner as regular Macintosh disks. OS/2 disks were read as PC DOS disks, due to fact that OS/2 used the FAT file system. At this time, Macs could also read and write UNIX file systems with the help of extra software. System 7 allowed users to access PC networks and allowed communication via TCP/IP and other compatible networking stacks. Actual PC software compatibility, however, required third party software such as SoftPC, which allowed some MS-DOS and early Microsoft Windows programs to run, or Connectix Virtual PC, which allowed the Mac to run Windows via full PC emulation. Other PC compatibility solutions took a more native approach by running Windows and MS-DOS by using x86 expansion cards with an x86 chip on the card. Apple offered some systems configured this way, marketed as "DOS Compatible"—a card with dedicated x86 CPU and RAM was used, while the Mac hard drive, sound subsystem, networking and input provided services to the PC. The PC could run simultaneously with the Mac, and the user could switch between the two in a fashion similar to a KVM switch. The earliest of these systems were 680x0 based systems running System 7. System 7 provided the support for accessing the PC volume from the Mac through its own PC Exchange software, and actual control of the PC hardware was accomplished by way of control panels. Miscellaneous At the time of its release, many users noticed that performance suffered as a result of upgrading from System 6 to System 7, though newer hardware soon made up for the speed difference. Another problem was System 7's large "memory footprint": System 6 could boot the system from a single 800k floppy disk and took up about of RAM, whereas System 7 used well over a megabyte. It was some time before the average Mac shipped with enough RAM built in for System 7 to be truly comfortable. System 7 was the first system release that could no longer be usefully run on floppy-only systems. Although most Macintosh models sold at the time included a hard disk as standard equipment, owners of older models were required to upgrade their hardware by buying either a new Mac or an external SCSI hard disk drive if they wished to run System 7. In order to take advantage of System 7's virtual memory feature, a Macintosh equipped with a paged memory management unit (PMMU) is required. The Motorola 68030 CPU has one built-in, and one can be added to the motherboard of the Motorola 68020-equipped Macintosh II. The other Macintosh model using an 68020, the Macintosh LC, cannot use virtual memory. Apple introduced the 68030-equipped Macintosh LC II shortly after System 7's introduction. Despite the newer processor, the LCII retained the earlier model's 16-bit bus and did not perform any faster than the LC it replaced. Despite these setbacks, System 7.0 was adopted quite rapidly by Mac users, and quickly became one of the base requirements for new software. The engineering group within Apple responsible for System 7 came to be known as the "Blue Meanies", named after the blue index cards on which were written the features that could be implemented in a relatively short time as part of Apple's operating system strategy. In comparison, the pink index card features were handled by the Pink group, later becoming the ill-fated Taligent project. System 7.0 was the last version of the Macintosh operating system that was available at no charge and could be freely redistributed. Although System 7 could be purchased from Apple, the cost was nominal and considered to only cover duplication and media. It was common for Macintosh dealers to allow customers to use the store's demo machines to copy System 7 install disks for the cost of a box of floppies. CD-ROM magazines such as Nautilus included System 7 on their disks. After Mac users downloaded thousands of copies of System 7 from the online services (AOL, CompuServe and GEnie), Apple surveyed the services and based on this popularity started selling the Mac OS as a retail product with System 7.1. Apple continued charging for major operating system upgrades until the release of OS X Mavericks in 2013. Version history Soon after the initial release of System 7, the 7.0.1 minor update was released in October 1991. A patch called "System 7 Tune-Up" also followed, which fixed the "disappearing files" bug in which the system would lose files and added "minimum" and "preferred" memory allotments to an application's Get Info box. System 7.1 In August 1992, the 7.1 update was released. This was the first version of the system software that Apple charged money for. Of this change, David Pogue wrote: New to 7.1 is the Fonts folder. This replaced the often time-consuming method of dragging fonts to and from the System file, introduced in System 7.0; it also replaced the Font/DA Mover application from System 6, which could also be used with 7.0. System 7.1 also included a lot of internal changes to support internationalization of dates, time, and numbers. It was also the first version to support "Enablers", which removed the requirement to release a new version of the system software every time new hardware was released. A set of specialized versions of 7.1, ranging from 7.1P1 to 7.1P6 (excluding 7.1P4) were created and included with various Performa models that were already available or were released after 7.1. These specialized versions included At Ease, Launcher, and some other changes that were integrated into later versions of the system software. The first major upgrade was System 7.1.1, also known as "System 7 Pro". This release was a bundle of 7.1 with AppleScript tools, QuickTime and Apple Open Collaboration Environment (AOCE). While System 7 had some trouble running on slightly older machines due to its memory footprint, System 7 Pro barely fit into any Macintosh computers of the time. It was most commonly used for its minor bug fixes rather than its new functionality. Apple joined the AIM alliance (Apple, IBM and Motorola) shortly after the release of System 7 in 1991, and started work on PowerPC-based machines that later became the Power Macintosh family. Support for these machines resulted in System 7.1.2. System 7.1.2 was never offered for retail sale; it shipped with the first batches of the PowerPC Macs and a 68k version shipped with a small number of Quadra 600 series systems. Later shipments shipped with System 7.5 instead. System 7.1.2P was the same as 7.1.2, and shipped with the Performa 630, LC 630 and Quadra 630 models that were released between July and November 1994. System 7.5 The next major release was System 7.5, which included bug fixes from previous updates and added several new features, including: An updated startup screen featuring a progress bar A new interactive help system called Apple Guide A clock in the menu bar (based on the free "SuperClock" control panel by Steve Christensen) An Apple menu item called Stickies (formerly a third-party application called "PasteIt Notes") which provided virtual Post-It Notes WindowShade, another former shareware control panel, provided the ability to condense a window down to its title bar. Introduced as a "minimize" feature to compete with Windows 95 as Mac OS had no taskbar or dock. MacTCP was bundled, enabling any Macintosh to connect to the Internet out of the box for the first time. The Control Strip (a fast way to change the system volume, control the playback of audio CDs, manage file sharing and printers and change the monitor resolution and color depth) was enabled on desktop Macintosh models for the first time. It had previously only been included with the PowerBook series. A new Desktop Patterns control panel allowed for tiled patterns up to 128x128 pixels with 8-bit color; previous versions were limited to 8x8 pixel tiles with a maximum of eight possible colors. Similar functionality was found on earlier system versions exclusive to Performa models and was housed in the General Controls panel. The Extensions Manager (enabling the user to turn extensions and control panels on and off; also based on a formerly third-party control panel) PowerTalk, a system-level email handling service and the originator of the Keychain system. The Launcher, a control panel containing shortcut buttons for frequently used programs (in a manner akin to the macOS Dock) A hierarchical Apple menu (folders within the Apple Menu Items folder would expand into submenus showing their contents. Again, based on a third party control panel; HAM by Microseeds publishing) System-wide drag & drop for text and other data (selections can be simply dragged with the mouse and dropped to their new destination, bypassing the clipboard) A scriptable Finder QuickDraw GX, a 2-D graphics rendering and geometry engine For the PowerPC only, an advanced, 3d Graphing Calculator, secretly developed at Apple by a former third party contractor Support for OpenDoc System 7.5 was codenamed "Capone", a reference to Al Capone and "Chicago", which was the code name for Microsoft's Windows 95, and was also the name of the default system font used in Mac OS until version 8. System 7.5.1 was primarily a bug fix of 7.5, but also introduced a new "Mac OS" startup screen in preparation for Mac clones. System 7.5.2, released only for the first PCI-based Power Macs, was notable for introducing Apple's new networking architecture, Open Transport. System 7.5.3, a major bug-fix update that also included Open Transport for other PowerPC-based machines as well as some 68k-based machines. 7.5.3 also made several improvements to the 68k emulator, and added translucent dragging support to the Drag Manager. It also included the first version of Control Strip to be compatible with all Macs. This was also the first version of Mac OS to support SMP. (9500/MP) System 7.5.3 Revision 2 included: performance enhancements; better reliability for PowerBooks using the third-party RAM Doubler program; improved reliability for PowerBook 500, 2300, and 5300 series computers with the PowerPC Upgrade Card; improved reliability when using the Startup Disk control panel; and improved reliability when copying files to 1 GB hard disks. System 7.5.3 Revision 2.1 was shipped with the Performa 6400/180 and 6400/200; this particular release was specific to these machines as there were stability problems with System 7.5.3 Release 2 on the new hardware, especially with the video card and transferring files over LocalTalk. System 7.5.4 was pulled due to a mistake at Apple, in which some components were not included in the installer. System 7.5.5 included significant performance improvements for virtual memory and memory management on PowerPC-based Macs, including the elimination of one type 11 error. Also included were a number of reliability improvements, such as fixes for Macs using floppy disks equipped with a DOS compatibility card, improved hard disk access for PowerPC PowerBooks and Performa 5400 through 9500 computers, fixes for Macs that included an Apple TV Tuner or Macintosh TV Remote Control, improvements to LocalTalk and networking (especially for the Performa 5400 and 6400), fixes to system startup for the faster 180 MHz Macs (which included PowerPC 604 or 604e processors), improved reliability when using sound-intensive applications on Quadra or Centris computers that contained the PowerPC upgrade card, and improved stability when using multiple background applications and shared printers on a network. System 7.5.5 is also the last System 7 release that can run on 68000-based Macs such as the Macintosh Plus and Macs with ROMs that lack support for 32-bit addressing such as Macintosh IIcx. 7.6 and later required a 68030 processor and 32-bit-addressing-capable ROM and will automatically turn on 32-bit addressing on boot. Mac OS 7.6 Mac OS 7.6 (codenamed "Harmony") was the last major update, released in 1997. With 7.6, the operating system was officially called "Mac OS" instead of "System". New features include a revamped Extensions Manager, more native PowerPC code for Power Macs, more bundled Internet tools and utilities, and a more stable Finder with increased memory allocation. In this version, the PowerTalk feature added in 7.5 was removed due to poor application support, and support for a large number of older Macintosh models was dropped. The minor update to Mac OS 7.6.1 finally ported the 68k exception handling routines to PowerPC, turning type 11 errors into less harmful errors (type 1, 2 or 3, usually) as crashing applications would more often terminate safely instead of crashing the operating system. Through this period, Apple had been attempting to release a completely new "modern" operating system, named Copland. When the Copland project was abandoned in 1996, Apple announced plans to release an OS update every six months until Rhapsody (which would by 2001 evolve into what was released as Mac OS X) shipped. Two more releases were shipped, now officially branded as "Mac OS" — Mac OS 7.6 and the minor bug fix 7.6.1. Future versions were released as Mac OS 8–8.6 and Mac OS 9–9.2. Table of releases See also List of Apple operating systems List of Macintosh software Inside Macintosh Mini vMac Project Star Trek References Notes Citations Bibliography Jim Carlton, Apple: The Inside Story of Intrigue, Egomania, and Business Blunders, Times Business/Random House, 1997. Amit Singh, Mac OS X Internals: A Systems Approach, Addison-Wesley, 2007. Further reading Harry McQuillen, 10 Minute Guide to System 7 (1991), Stuple, S. J., Macintosh System 7.5 For Dummies Quick Reference (1994), Bob Levitus, Macintosh System 7.5 for Dummies (November 1994), from apple.com from apple.com from apple.com from apple.com from apple.com from apple.com from apple.com from apple.com External links System 7 Today The Compact Mac Trio: System 6 or 7? System 7 Flash Simulation in 1-Bit Black and White System 7 Flash Simulation in Color PCE.js emulator running System 7 1991 software Classic Mac OS PowerPC operating systems

Operating System (OS)

BSD/OS BSD/OS (originally called BSD/386 and sometimes known as BSDi) is a discontinued proprietary version of the BSD operating system developed by Berkeley Software Design, Inc. (BSDi). BSD/OS had a reputation for reliability in server roles; the renowned Unix programmer and author W. Richard Stevens used it for his own personal web server. History BSDi was formed in 1991 by members of the Computer Systems Research Group (CSRG) at UC Berkeley to develop and sell a proprietary version of BSD Unix for PC compatible systems with Intel 386 (or later) processors. This made use of work previously done by Bill Jolitz to port BSD to the PC platform. BSD/386 1.0 was released in March 1993. The company sold licenses and support for it, taking advantage of terms in the BSD License which permitted use of the BSD software in proprietary systems, as long as credit was given to the author. The company in turn contributed code and resources to the development of non-proprietary BSD operating systems. In the meantime, Jolitz had left BSDi and independently released an open source BSD for PCs, called 386BSD. One of the advantages of the BSDi system was a complete and thorough manpage documentation for the entire system, including complete syntax and argument explanations, examples, file usage, authors, and cross-references to other commands. Manpage documentation is far poorer in modern Linux systems. BSD/386 licenses (including source code) were priced at $995, much less than AT&T UNIX System V source licenses, a fact highlighted in their advertisements. As part of the settlement of USL v. BSDi, BSDI substituted code that had been written for the University's 4.4 BSD-Lite release for disputed code in their OS, effective with release 2.0. By the time of this release, the "386" designation had become dated, and BSD/386 was renamed "BSD/OS". Later releases of BSD/OS also supported Sun SPARC-based systems. BSD/OS 5.x versions were available for PowerPC too. The marketing of BSD/OS became increasingly focused on Internet server applications. However, the increasingly tight market for Unix-compatible software in the late 1990s and early 2000s hurt sales of BSD/OS. On one end of the market, it lacked the certification of the Open Group to bear the UNIX trademark, and the sales force and hardware support of the larger Unix vendors. Simultaneously, it lacked the negligible acquisition cost of the open source BSDs and Linux. BSD/OS was acquired by Wind River Systems in April 2001. Wind River discontinued sales of BSD/OS at the end of 2003, with support terminated at the end of 2004. Releases References Berkeley Software Distribution Discontinued operating systems

Operating System (OS)

List of disk operating systems called DOS This is a list of disk operating systems in which the acronym DOS is used to form their names. Many of these are simply referred to as "DOS" within their respective communities. MS-DOS / IBM PC DOS compatible systems MS-DOS (since 1981), Microsoft operating system based on 86-DOS for x86-based personal computers IBM PC DOS (since 1981), OEM version of MS-DOS for the IBM Personal Computer and compatibles, manufactured and sold by IBM from the 1980s to the 2000s DR-DOS (since 1988), MS-DOS-compatible operating system originally developed by Digital Research ROM-DOS (1989), MS-DOS clone by Datalight PTS-DOS (since 1993), MS-DOS clone developed in Russia by PhysTechSoft FreeDOS (since 1998), open source MS-DOS clone Other x86 disk operating systems with "DOS" in the name 86-DOS (a.k.a. QDOS, created 1980), an operating system developed by Seattle Computer Products for its 8086-based S-100 computer kit, heavily inspired by CP/M Concurrent DOS (a.k.a. CDOS, Concurrent PC DOS and CPCDOS) (since 1983), a CP/M-86 and MS-DOS 2.11 compatible multiuser, multitasking DOS, based on Concurrent CP/M-86 developed by Digital Research DOS Plus (since 1985), a PC DOS and CP/M-86 compatible multitasking operating system for early x86-based personal computers, based on Concurrent PC DOS 4.1/5.0 by Digital Research Multiuser DOS (a.k.a. MDOS), a PC DOS and CP/M-86 compatible multiuser multitasking operating system based on Concurrent DOS by Digital Research NetWare PalmDOS, a successor of DR DOS 6.0 specifically tailored for early mobile and palmtop PCs by Novell Novell DOS, a multitasking successor of DR DOS 6.0 by Novell OpenDOS, a successor of Novell DOS by Caldera Disk operating systems for other platforms AmigaDOS, the disk operating system portion of AmigaOS AMSDOS, for Amstrad CPC compatibles ANDOS, operating system for the Russian Electronika BK computers Apple DOS, operating system for the Apple II series from late 1978 through early 1983 Apple ProDOS, name for both ProDOS 8 for the Apple II and ProDOS 16 for the Apple IIGS Atari DOS, for the Atari 8-bit family of home computers Commodore DOS, for Commodore's 8-bit computers Cromemco DOS (CDOS), a CP/M-like operating system CSI-DOS, for the Soviet Elektronika BK computers DOS (Diskette Operating System), a small OS for 16-bit Data General Nova computers, a cut-down version of their RDOS. DEC BATCH-11/DOS-11, the first operating system to run on the PDP-11 minicomputer Delta DOS, third party option from Premier Microsystems for the Dragon 32/64 DIP DOS, the operating system of the Atari Portfolio DOS/360, 1966 IBM System/360 mainframe computer Disk Operating System DOS XL, Atari 8-bit family DOS from Optimized Systems Software DragonDOS, for the Dragon 32/64 GEMDOS, one of the components of the Atari TOS IS-DOS, for Russian ZX Spectrum clones, developed in 1990 or 1991 MasterDOS, replacement DOS for the SAM Coupé MDOS, Myarc Disk Operating System for the Geneve 9640 MSX-DOS, a cross between MS-DOS 1.0 and CP/M developed by Microsoft for the MSX computer standard MyDOS, third-party Atari 8-bit family DOS NewDos/80, Apparat's feature-rich alternative to TRSDOS for the TRS-80. Oric DOS, for the Oric-1 home computer PTDOS, for the 1970s Sol-20 from Processor Technology SAMDOS, original DOS for the SAM Coupé Sinclair QDOS, for the Sinclair QL RDOS, a real-time operating system released in 1972 for the Data General Nova and Eclipse minicomputers SK*DOS, for Motorola 68000-based systems SmartDOS, third-party Atari 8-bit family DOS SpartaDOS, third-party Atari 8-bit family DOS TOP-DOS, third-party Atari 8-bit family DOS TR-DOS, for the ZX Spectrum TRSDOS, for the Tandy TRS-80 line of 8-bit Zilog Z80 microcomputers Xtal DOS for the Tatung Einstein See also DOS (disambiguation) DOS 1 (disambiguation) DOS 2 (disambiguation) DOS 3 (disambiguation) DOS 4 (disambiguation) DOS 5 (disambiguation) DOS 6 (disambiguation) DOS 7 (disambiguation) DOS 8 (disambiguation) DOS 10 (disambiguation) DOS 20 (disambiguation) DOS 30 References D

Operating System (OS)

86-DOS 86-DOS is a discontinued operating system developed and marketed by Seattle Computer Products (SCP) for its Intel 8086-based computer kit. Initially known as QDOS (Quick and Dirty Operating System), the name was changed to 86-DOS once SCP started licensing the operating system in 1980. 86-DOS shared a few of its commands with other operating systems like OS/8 and CP/M, which made it easy to port programs from the latter. Its application programming interface was very similar to that of CP/M. The system was licensed and then purchased by Microsoft and developed further as MS-DOS and PC DOS. History Origins 86-DOS was created because sales of the Seattle Computer Products 8086 computer kit, demonstrated in June 1979 and shipped in November, were languishing due to the absence of an operating system. The only software that SCP could sell with the board was Microsoft's Standalone Disk BASIC-86, which Microsoft had developed on a prototype of SCP's hardware. SCP wanted to offer the 8086-version of CP/M that Digital Research had initially announced for November 1979, but it was delayed and its release date was uncertain. This was not the first time Digital Research had lagged behind hardware developments; two years earlier it had been slow to adapt CP/M for new floppy disk formats and hard disk drives. In April 1980, SCP assigned 24-year-old Tim Paterson to develop a substitute for CP/M-86. Using a CP/M-80 manual as reference Paterson modeled 86-DOS after its architecture and interfaces, but adapted to meet the requirements of Intel's 8086 16-bit processor, for easy (and partially automated) source-level translatability of the many existing 8-bit CP/M programs; porting them to either DOS or CP/M-86 was about equally difficult, and eased by the fact that Intel had already published a method that could be used to automatically translate software from the Intel 8080 processor, for which CP/M had been designed, to the new 8086 instruction set. At the same time he made a number of changes and enhancements to address what he saw as CP/M's shortcomings. CP/M cached file system information in memory for speed, but this required a user to force an update to a disk before removing it; if the user forgot, the disk would become corrupt. Paterson took the safer, but slower approach of updating the disk with each operation. CP/M's PIP command, which copied files, supported several special file names that referred to hardware devices such as printers and communication ports. Paterson built these names into the operating system as device files so that any program could use them. He gave his copying program the more intuitive name COPY. Rather than implementing CP/M's file system, he drew on Microsoft Standalone Disk BASIC-86's File Allocation Table (FAT) file system. By mid-1980 SCP advertised 86-DOS, priced at for owners of its 8086-board and for others. It touted the software's ability to read Zilog Z80 source code from a CP/M disk and translate it to 8086 source code, and promised that only "minor hand correction and optimization" was needed to produce 8086 binaries. IBM interest In October 1980, IBM was developing what would become the original IBM Personal Computer. CP/M was by far the most popular operating system in use at the time, and IBM felt it needed CP/M in order to compete. IBM's representatives visited Digital Research and discussed licensing with Digital Research's licensing representative, Dorothy Kildall (née McEwen), who hesitated to sign IBM's non-disclosure agreement. Although the NDA was later accepted, Digital Research would not accept IBM's proposal of in exchange for as many copies as IBM could sell, insisting on the usual royalty-based plan. In later discussions between IBM and Bill Gates, Gates mentioned the existence of 86-DOS and IBM representative Jack Sams told him to get a license for it. Creation of PC DOS Microsoft purchased a non-exclusive license for 86-DOS from Seattle Computer Products in December 1980 for . In May 1981, it hired Tim Paterson to port the system to the IBM PC, which used the slower and less expensive Intel 8088 processor and had its own specific family of peripherals. IBM watched the developments daily, submitting over 300 change requests before it accepted the product and wrote the user manual for it. In July 1981, a month before the PC's release, Microsoft purchased all rights to 86-DOS from SCP for . It met IBM's main criteria: it looked like CP/M, and it was easy to adapt existing 8-bit CP/M programs to run under it, notably thanks to the TRANS command which would translate source files from 8080 to 8086 machine instructions. Microsoft licensed 86-DOS to IBM, and it became PC DOS 1.0. This license also permitted Microsoft to sell DOS to other companies, which it did. The deal was spectacularly successful, and SCP later claimed in court that Microsoft had concealed its relationship with IBM in order to purchase the operating system cheaply. SCP ultimately received a  million settlement payment. Intellectual property dispute When Digital Research founder Gary Kildall examined PC DOS and found that it duplicated CP/M's programming interface, he wanted to sue IBM, which at the time claimed that PC DOS was its own product. However, Digital Research's attorney did not believe that the relevant law was clear enough to sue. Nonetheless, Kildall confronted IBM and persuaded them to offer CP/M-86 with the PC in exchange for a release of liability. Controversy has continued to surround the similarity between the two systems. Perhaps the most sensational claim came from Jerry Pournelle, who said that Kildall personally demonstrated to him that DOS contained CP/M code by entering a command in DOS that displayed Kildall's name, but Pournelle never revealed the command and nobody has come forward to corroborate his story. A 2004 book about Kildall says that he used such an encrypted message to demonstrate that other manufacturers had copied CP/M, but does not say that he found the message in DOS; instead Kildall's memoir (a source for the book) pointed to the well-known interface similarity. Paterson insists that the 86-DOS software was his original work, and has denied referring to or otherwise using CP/M code while writing it. After the 2004 book appeared, he sued the authors and publishers for defamation. The court ruled in summary judgment that no defamation had occurred, as the book's claims were opinions based on research, or were not provably false. CP/M and DOS source code comparison In 2016, Bob Zeidman from Zeidman Consulting, compared CP/M by Digital Research Inc. and DOS by Tim Paterson (the developer who was originally contracted by Microsoft to write DOS) in order to determine whether the original DOS source code had been copied from CP/M source code as had been rumored for many years. If commands in DOS and CP/M are compared, only a few of them coincide partially. In fact, there are more similarities between DOS and OS/8 commands, than between DOS and CP/M commands. This is due to the fact that all these commands consist of English words which directly describe the action to be performed. However, after analyzing the system calls in both operating systems, it becomes apparent that DOS system calls were definitely copied from the CP/M system calls. Given the quantity of identical numbers representing identical functions, it is clear that Tim Paterson referenced the CP/M manual when writing DOS. Zeidman's conclusion is that DOS did not copy any code from CP/M. However, a substantial number of the system calls were copied. According to Zeidman, "Digital research could have brought a legitimate copyright claim against Microsoft for copying a substantial number of system calls". Should that have been the case, "Microsoft could have claimed a fair use defense because the fact that many of the system commands used the same numbers did not reduce the market for CP/M". Versions Features Commands The following list of commands is supported by 86-DOS. Internal commands CLEAR COPY DIR ERASE RENAME TYPE External commands ASM CHKDSK DEBUG EDLIN HEX2BIN MAKRDCPM RDCPM SYS TRANS EDLIN By 1982, when IBM asked Microsoft to release a version of DOS that was compatible with a hard disk drive, PC DOS 2.0 was an almost complete rewrite of DOS, so by March 1983, very little of 86-DOS remained. The most enduring element of 86-DOS was its primitive line editor, EDLIN, which remained the only editor supplied with Microsoft versions of DOS until the June 1991 release of MS-DOS 5.0, which included a text-based user interface editor called MS-DOS Editor, based on QBasic. EDLIN can still be used on contemporary machines, since there is an emulated DOS environment up to Windows 10 (32 bit). Supported disk formats Seattle Computer Products' 86-DOS supported the FAT12 filesystem on a range of 8-inch and 5.25-inch floppy disk drives on S-100 floppy disk controller hardware manufactured by Cromemco, Tarbell Electronics and North Star Computers. The Western Digital FD1771-based Cromemco and Tarbell boards supported one-sided, single-density soft-sectored drives. A Tarbell double-density board utilizing the FD1791 was supported as well. Later, SCP offered advanced floppy disk controllers, like the Disk Master series. 86-DOS did not take advantage of a FAT ID byte or BIOS parameter block (BPB), as later DOS versions do, to distinguish between different media formats; instead different drive letters were hard-coded at time of compilation to be associated with different physical floppy drives, sides and densities. That meant, depending on its type, a disk had to be addressed under a certain drive letter to be recognized correctly. This concept was later emulated with more flexibility by DRIVER.SYS under DOS 3.x and later versions. Two logical format variants of the 86-DOS 12-bit FAT format existed — the original format with 16-byte directory entries and the later format (since 86-DOS 0.42) with 32-byte directory entries. Only the second one is logically compatible with the FAT12 format known since the release of MS-DOS and PC DOS. MS-DOS still cannot mount such volumes, as in absence of a BPB it falls back to retrieve the FAT ID in the FAT entry for cluster 0 to choose among hard-coded disk geometry profiles. In all formats of a volume formatted under MS-DOS that would otherwise be supported by both systems and typically also in all other formats, this ID is located in the first byte of logical sector 1 — that is, the volume's second sector with physical cylinder-head-sector (CHS) address 0/0/2 or logical block addressing (LBA) address 1 — since MS-DOS assumes a single reserved sector, the boot sector. Under 86-DOS, the reserved sectors area is significantly larger (whole tracks), and therefore the prototypical FAT ID (and ) is located elsewhere on disk, making it impossible for MS-DOS to retrieve it, and even if it would, the hard-coded disk profile associated with it would not take this larger reserved sectors region under 86-DOS into account. CP/M 2 floppy media were readable through RDCPM. 86-DOS did not offer any specific support for fixed disks, but third-party solutions in form of hard disk controllers and corresponding I/O system extensions for 86-DOS were available from companies like Tallgrass Technologies, making hard disks accessible similar to superfloppies within the size limits of the FAT12 file system. Various OEM versions of MS-DOS 1.2x and 2.x supported a number of similar 8.0 in FAT12 floppy disk formats as well, although not identical to those supported by 86-DOS. Disk formats supported by one of the last versions developed by Tim Paterson at Microsoft, MS-DOS 1.25 (March 1982) for the SCP Gazelle computer with SCP controller or Cromemco 16FDC controller (by default, this version only supported the MS-DOS-compatible variants of the 8.0 in formats with a single reserved sector but it could be built to provide two extra drive letters to read and write floppies in the previous SCP 86-DOS 8.0 in disk formats since 0.42 as well): In 1984 Seattle Computer Products released an OEM version of MS-DOS 2.0 for the SCP S-100 computer with SCP-500 Disk Master Floppy controller. It added support for 5.25 in DD/1S (180 KB) and DD/2S (360 KB) FAT12 formats and supported the older formats as well, although possibly with some of the parameters modified compared to MS-DOS 1.25. See also MIDAS MSX-DOS Notes References Further reading (41 pages) External links 86-DOS documentation from Paterson Technology Run SCP 86-DOS 1.0 in the Altair 8800 SIMH simulator by Howard M. Harte Microcomputer software Disk operating systems DOS variants Floppy disk-based operating systems Discontinued operating systems Proprietary operating systems 1979 software Assembly language software

Operating System (OS)

OS 2200 OS 2200 is the operating system for the Unisys ClearPath Dorado family of mainframe systems. The operating system kernel of OS 2200 is a lineal descendant of Exec 8 for the UNIVAC 1108. Documentation and other information on current and past Unisys systems can be found on the Unisys public support website. See Unisys 2200 Series system architecture for a description of the machine architecture and its relationship to the OS 2200 operating system. History There were earlier 1100 systems going back to the 1101 in 1951, but the 1108 was the first 1100 Series computer designed for efficient support of multiprogramming and multiprocessing. Along with this new hardware came the operating system Exec 8 (Executive System for the 1108). The UNIVAC 1108 computer was announced in 1964 and delivered in late 1965. The first 1108 computers used Exec I and Exec II, which had been developed for the UNIVAC 1107. However, UNIVAC planned to offer symmetric multiprocessor versions of the 1108 with up to 4 processors and the earlier operating systems (really basic monitor programs) weren't designed for that, even though they supported limited multiprogramming. When the UNIVAC 1110 was introduced in 1972, the operating system name was changed to OS 1100 to reflect its support for the wider range of systems. The name OS 1100 was retained until 1988 with the introduction of the Sperry 2200 Series as a follow on to the 1100 Series when its name was changed to OS 2200. Since that time, the 2200 Series became the Unisys ClearPath IX Series and then the Unisys ClearPath Dorado Series, but the operating system retained the OS 2200 name. The company name and its product names also changed over time. Engineering Research Associates (ERA) of Saint Paul was acquired by Remington Rand Corporation. Remington Rand also acquired the Eckert–Mauchly Computer Corporation of Philadelphia which was then building the UNIVAC computer. The two were combined into the UNIVAC division of Remington Rand under the direction of William Norris. William Norris had been one of the founders of ERA and later left Remington Rand to start Control Data Corporation. The UNIVAC division of Remington Rand Corporation became the UNIVAC division of Sperry Rand Corporation after Remington Rand merged with Sperry Corporation. In the 1970s Sperry Rand began a corporate identity program that changed its name to Sperry Corporation and all the division names to begin with Sperry, so the computer systems division became Sperry UNIVAC. Later the division names were dropped and everything simply became Sperry. The operating system kernel is still referred to as "the Exec" by most Unisys and customer personnel. However, when Unisys began releasing suites of products tested together as system base releases, later called "ClearPath OS 2200 Release n", the term OS 2200 changed to refer to the entire suite of products in the system release and others, such as BIS, released asynchronously for the Dorado hardware platforms. In 1986 Burroughs and Sperry corporations merged to become Unisys (which some long time 2200 Series clients say stands for "UNIVAC Is Still Your Supplier"). The major mainframe product lines of both companies have continued in development including the MCP Operating System from Burroughs and OS 2200 from Sperry. In 2016 Unisys made a virtual Microsoft Windows version of OS2200 available at no cost for educational and leisure purposes. Exec 8 EXEC 8 (sometimes referred to as EXEC VIII) was UNIVAC's operating system developed for the UNIVAC 1108 in 1964. It combined the best features of the earlier operating systems, EXEC I and EXEC II, which were used on the UNIVAC 1107. EXEC 8 was one of the first commercially successful multiprocessing operating systems. It supported simultaneous mixed workloads comprising batch, time-sharing and real-time. Its one file system had a flat naming structure across many drums and spindles. It also supported a well-received transaction processing system. Previous systems were all real-mode systems with no hardware support for protection and separation of programs and the operating system. While there had been support for multiprogramming in previous systems, it was limited to running one user job concurrently with multiple supporting functions known to be well-behaved, such as the card reader, printer, and card punch spoolers. The Exec 8 operating system was designed from the very beginning to be a multiprogramming and multiprocessing operating system because the 1108 was designed to have up to four CPUs. Memory and mass storage were the primary system constraints. While the 1100 Series was envisioned as targeting a more general market, extreme real time processing was a primary requirement. The specifications for Exec 8 were drawn up by December 1964 as a preliminary Programmers Reference Manual (user guide) and work began in May 1965. Exec 8 began as a real time operating system with early use mostly in general scientific and engineering work, but it was also used in message switching, process control, simulation, and missile firing control. It was designed to run on systems that often had only 128K words (576 K bytes—less than the maximum memory size for the IBM PC XT), and was focused on real time and batch processing. While the earliest release levels did work in 128KW, increasing functionality in later releases made that untenable, since it didn't leave enough space for programs of useful size. The maximum memory capacity of an 1108 was 256KW (1,148 KB) so efficient use of memory was the most important constraint since core memory was the most expensive part of the system. Mass storage consisted of 6-foot long rotating drums that held 256KW (in the FH-432) to 2MW (in the FH-1782). The highest capacity mass storage was the FASTRAND drum, which held 22 MW (99 MB). File fragmentation was dealt with by a process called a "file save", which was generally done once per day, at night. It involved rolling all files out to tape, reinitializing the drum file system, then reading the files back in. With severe memory constraints and real time use, keeping only a single copy of code loaded into core was a requirement. Since the 1108 was designed for multitasking, the system was fully "reentrant" (thread safe). Each reentrant module accessed program data through a single memory "base address", which was different for each instance of run data. Switching execution contexts could be done in a single instruction merely by setting a different base address in a single register. The system used fine-grained locking to protect shared data structures. The executive, compilers, utilities, and even sophisticated user applications that might have multiple copies running concurrently were written so that their code could be shared. This required loading only one copy into memory, saving both space and the time it took to load the code. Another reason to separate code and data into different load entities was that memory was implemented as two independent banks (separate physical cabinets) called IBANK and DBANK (instruction and data). Each had its own access path, so the CPU could read both banks simultaneously. By loading executable code into one memory bank and data into the other, the run time of many programs could be almost halved. Reentrant code had to be thread safe (execute only); self-modifying code was not allowed. For other programs, modifying executable code during runtime was still an acceptable programming technique in the time of 1100-series computers, but users were encouraged not to do it because of the performance hit. Security benefits were touted but not highly valued because hacking most 1100-series applications would provide no benefit to anyone, and because few hackers were malevolent then. Exec 8 was primarily a batch processing system that gave applications (called "tasks") very fine control of CPU scheduling priority for its threads (called "activities"). Processor switching was preemptive, with higher priority threads gaining control of the processor currently running the lowest priority thread of any program. Except in realtime systems, even the lowest priority tasks got some processor time. It was a multiprogramming and multiprocessing operating system with fully symmetric processor management. A test-and-set instruction built into the hardware allowed very efficient and fine-grained locking both within the OS and within multi-threaded applications. In Exec 8, work is organized into jobs, called "runs," which are scheduled based on their priority and need for lockable resources such as Uniservo tape drives or Fastrand drum files. The control language syntax uses the "@" symbol (which Univac called "the master space") as the control statement recognition symbol. It was immediately followed by the command or program name, then a comma and any option switches. After a space character, the remainder of the statement differed for particular commands. A command to compile a FORTRAN program would look like "@FOR[,options] sourcefile, objectfile". Input data for an application could be read from a file (generally card images), or immediately follow the @ command in the run stream. All lines until the sentinel command "@END" were assumed to be input data, so forgetting to insert it led to the compiler interpreting subsequent commands as program data. For this reason, it was preferable to process data in files rather than inputting it in the run stream. In 1968, work began on adding time-sharing capability to Exec 8. It was delivered with level 23 of the executive in 1969. Time sharing (called demand mode) had the same capabilities as batch and real time processes. Everything that could be done in batch could be done from an ASCII terminal. In demand mode, job stream I/O was attached to a terminal handler rather than card image (input) and spool (output) files. The same run control language was used for both. A few years later, more specific time sharing commands were added, and some control statements could be issued asynchronously for immediate processing, even when neither the executive or the running program were expecting data. Those commands, which could be entered only from a terminal, began with "@@". Because they could be performed without stopping other work in progress from the same terminal, they were called transparent commands. At first these were just statements to kill the current program or redirect terminal output to a file, but eventually, almost all control statements were allowed to be "immediate." Both batch and demand runs terminate with an @FIN statement, and if a demand user terminates his session while his run is active, the Exec automatically terminates the run without requiring @FIN. Communications software A transaction processing capability was developed in the late 1960s as a joint project with United Airlines and later refined in another joint project with Air Canada. This capability was fully integrated into the operating system in 1972 and became the basis of much of the future growth of the 1100 Series. Early users controlled communication lines directly from within their real time programs. Part of the development of transaction processing included a communication message system that managed the communication lines and presented messages to Exec 8 to be scheduled as transactions. This moved all the low level communication physical line management and protocols out of the applications and into the CMS 1100 application. CMS 1100 itself ran as a real time multi-threaded program with the privilege of acquiring control of communication lines and submitting transaction messages for scheduling. This led to the notions in Exec 8 that applications of any nature needed to be carefully controlled to ensure that they could not cause integrity issues. Security was certainly a concern, but in the early days system reliability and integrity were much larger issues. The system was still primarily batch and transaction processing and there was little chance that anyone could install unauthorized code on the system. CMS 1100 later added the capability to be the interface for demand terminals as well as transaction terminals so that terminals could be used for both and the early terminal drivers could be removed from the Exec. CMS 1100 was later replaced by a combination of CPComm (ClearPath Enterprise Servers Communications Platform) and SILAS (System Interface for Legacy Application Systems). For the Intel-based Dorado server models, the lower level communications were moved to firmware, with the upper levels handled by SILAS and CPCommOS (ClearPath Enterprise Servers Communications Platform for Open Systems). The Exec The Exec contains all the code in the system that is allowed to run at the highest privilege levels. There are no mechanisms for other code to be promoted to those privilege levels. The Exec is responsible for managing the system hardware, scheduling and managing work, and communicating with operators and administrators. In Release 16.0, the Exec is level 49R2 (49.70.5). The internal system levels use a three-part number such as 21.92.42 (which was the first widely used production system although earlier releases were used in production at a number of sites). The first number part is the major level and indicates a new version of the Exec with all previous updates integrated into a new base version. This is an infrequent process and occurs at intervals of years. The second number part indicates versions of updates to the major level and often occurs several times per week. When a decision is made to freeze the feature content and prepare for release, the third part comes into play and indicates versions of the pre-release level as fixes and minor feature updates are applied. Concurrently with preparing a level for release, updates to the "mainline" continue as engineers integrate changes in preparation for a future release. For many years the official release level was the full three-part number. Later releases were named simply 44R1, 44R2, 49R2, and so on although the three-part number is still used internally. Performing work The Exec is at heart a real time, multi-threaded batch processing system. Everything has been built around that model. The Exec itself is largely structured as a real time program. Functions that are performed as Services in Windows or Daemons in Linux and UNIX are implemented as either activities within the Exec or as batch programs that are always running in the background. Time-sharing (known as demand mode) and transaction processing are implemented as special cases of batch. One result is that there are few restrictions on what a time-sharing user or transaction program can do. There are many warnings for writers of transaction programs that they will not be happy with performance if for example they call for a tape mount, but it is permitted. The largest unit of work is the "Run." This is taken from the factory "production run" terminology and generally equates to job or session on other systems. A Run is defined by its "run stream." A run stream is a sequence of control statements that represent the steps to be taken. They may include file handling, program execution, and branches of control. A batch Run is typically stored as a file and is scheduled by a "Start" command from within another Run or by the operator. A time sharing Run is initiated by logging in from a time-sharing terminal and inputting the @RUN command. Often the @RUN statement and the second control statement (often @ADD or a program execution) are generated automatically based on the user profile. Security authorizations are validated based on the authenticated user-id and other information supplied on the Run control statement. Transactions are a special case. There aren’t actually any control statements, but the internal data structures of a run are created. This enables the Exec to associate the same security, accounting, debugging, etc. mechanisms with transaction programs. Generally a security profile is cached in memory at the time the transaction user is authenticated and is copied from the user's session data to the transaction run state when the transaction is scheduled. Because each transaction instance is essentially a Run, accounting, logging, and error handling are all encapsulated by the Run mechanism. Batch Batch jobs (Runs) are characterized by having a runstream (job control language statements) stored in a file. A batch job always contains an @RUN statement as the first record in the file. This statement gives the run a name (runid), defines priorities, and defines the maximum number of SUPS (Standard Units of Processing) the job is expected to use. The job is started from some other job with a @START control statement or by the operator via an ST keyin. The system may be configured to automatically issue @START statements for any number of jobs when it boots. These jobs serve the purpose of performing initialization, recovery, and background functions. All of the fields on the @RUN statement may be overridden by corresponding fields on the @START statement. Except when the @START is executed by a privileged user, the userid and other security state are always taken from the run doing the @START. There are two priority fields on the @RUN statement. One is used to specify the backlog priority. There are 26 backlog priority levels (A – Z). The Exec has a configured maximum number of open batch runs. When that level is reached, jobs are then selected from the backlog queues in priority order. Within a priority selection is usually FIFO. However, the Exec pre-scans the job control statements up to the first program execution looking for file names and reel numbers. If the job would immediately stall because some resources it needs are not available, it may be bypassed to start other jobs at the same priority level. The second priority level defines an execution processor resource group. In general higher execution group priorities typically get more processor time. While the OS 2200 job control language does not support full programmability, it does allow dynamic additions of sequences of control language through an @ADD control statement. The file to be added may have been created by the same job immediately preceding adding it. The @ADD and most other control statements may also be submitted from within a running program via an API. Additional programmability is available indirectly through the use of the Symbolic Stream Generator (SSG). SSG is a programming language for manipulating and creating text files from input parameters and system information. It is used heavily for configuration management (make) processing and other functions where text images need to be created programmatically. The resulting output can be "@ADD"ed in the same run thus providing the indirectly programmable runstream. Operator commands are available to change both the backlog and execution priorities of runs. As all operator commands are available by API to suitably privileged users, this can be automated or controlled by a remote administrator. Deadline is a special case of batch. A deadline run looks just like any other batch run except that a deadline time is specified on the @RUN or @START control statement. The deadline time is used in conjunction with the maximum SUPS (time estimate) on the control statement. A deadline job runs at normal batch priorities unless or until it appears that it could miss its deadline time. Then the more the mismatch between time until the deadline and remaining SUPS, the higher the priority. While deadline can’t totally shut off transactions and has no effect on real time, it can effectively shut off most other processing in the system if necessary to achieve its goal. Demand OS 2200 time-sharing sessions are called demand (from "on demand") runs. They use the same control language as batch runs with a few additions known as "immediate" control statements. Immediate control statements use the "@@" sentinel which indicates that they are to be executed immediately even if a program is running. While they can be used to create or assign files, the most important ones allow a demand user to error terminate a running program or even send it a signal. Transactions Transactions execute as runs but without any stored or submitted control statements. Instead when a message is received from a session defined as a transaction session, it is scanned to determine the transaction queue on which it is to be placed. This is normally determined by the first characters of the message but user-written scanners may be added. The communication manager, which is capable of handling up to 250,000 active sessions, takes incoming transaction messages and passes them to the message queuing software. It can handle an unlimited number of queued messages using the message queuing architecture. A call is made to the Transaction Interface Package (TIP) APIs in the operating system to queue the transaction on the appropriate queuing point. Each queuing point identifies the priority and concurrency level of the work and the associated transaction program to be executed. A transaction program scheduling tree allows the client to establish relative usage for groups of transaction programs. Concurrency limits avoid one type of work dominating the system to the exclusion of other work and avoid creating an over commitment of resources. Up to 4094 nodes may be created in the tree. Maximum concurrency specified for each node in the tree Concurrency of higher node limits total concurrency of dependent nodes Concurrency of highest node limits system concurrency Priority (0 to 63) and concurrency level (1 to 2047) can be specified for each transaction program. The highest priority transaction is selected for scheduling except as limited by the concurrency policies in effect for its node and higher nodes. Real time Real time is not another type of run. Rather it is a set of priority levels which any activity may request. Real time is most typically used by long running batch programs, like the OS 2200 communications manager CPComm, but is not restricted to such. There are 36 real time priority levels available by API for applications to use. The user and account must have the privilege to use real time priorities. It is up to the site to control how their applications use the priority levels. Real time priorities totally dominate all lower priorities so it's quite possible for a misbehaved real time program to tie up one or more processors. The real time priority applies to an individual activity (thread) so a program may have both real time and non-real time threads executing at the same time. CPU dispatch Once a run has been started, getting access to the processor controls its rate of progress. The heart of the Exec is the Dispatcher which manages all the processors. The Exec supports up to 4095 dispatching priorities although most sites define only a small subset of those. The two highest "priorities" aren’t switchable. They are recognition of certain types of processing that must be allowed to continue on the processor on which they started until they voluntarily give up control. Interrupt lockout occurs when an interrupt arrives or in a few special cases when other Exec code prevents all interrupts (in order to change some data that an interrupt handler may also access). Interlock is used by interrupt post processing routines that either need to run on the same physical processor or simply should not be interrupted. The Dispatcher, I/O completions, and I/O initiation are some examples. All locks used by both of these priorities are spin locks as the only way they can be set by someone else is on another processor and the design requires that they only be set for very short instruction sequences. High Exec priority is used by the operator command handler and some other functions that may have to run even when a real time program has control. They are expected to use only very short amounts of time. If they need more time, they should queue the work to be processed by a Low Exec activity. Real time activities have an unlimited processor quantum and run without switching unless interrupted by a higher priority real time activity or High Exec activity. Real Time activities are given control of any available processor that is running something of lower priority. Interrupts are sent between processors when necessary to ensure immediate availability. Real time is used by customers to fly missiles, run simulators, and other functions that require immediate response. Transaction priorities may be handled in two ways as defined by the site. They may be a sort of lower priority real time in that only the priority matters and the quantum size is essentially infinite. This is appropriate for very short-lived transactions such as airline reservations; if one loops due to a programming error, the Exec will terminate it when it reaches its very small configured maximum time. The other form allows the Exec to vary the priority within a range to optimize system resource usage. The approach gives higher priority and shorter time slices to programs that are I/O limited and progressively lower priorities but longer time slices to those that are computing. The Exec dynamically adjusts these priorities based on behavior as programs often behave both ways at different times. This approach is appropriate for longer running transactions like database queries or airline fare quotes. Batch and demand always use dynamically adjusted priorities. Programs that are I/O limited or are in a conversation with a time-sharing user get higher priorities but short time slices. More compute-oriented programs get lower priorities and longer time slices. The Exec has two additional mechanisms for optimizing dispatching. One is affinity-based dispatching. When possible the Exec will run an activity on the same processor that it was on the last time to get the greatest advantage of residual cache contents. If that isn't possible it tries to keep the activity on the "nearest" processor from the standpoint of cache and memory access times. The second is a "fairness" policy mechanism. The site can define the relative percentage of resources to be allocated to each of transactions, demand and batch. Within transactions and batch there are priority groupings that can further indicate what percentage of their group's time is to be allocated to the priority. This ensures that transactions cannot so dominate the system that no batch work gets done. Within the various priority groupings it ensures that some progress can be assured for each group (unless the group percentage is zero). These "fairness" algorithms only come into play when the processors are very busy, but OS 2200 systems often run with all processors at near 100% utilized. Metering OS 2200 supports several models for system performance management. Customers may purchase a certain fixed performance level, and the Exec will monitor processor usage to ensure that performance does not exceed that level. Customers can also purchase additional performance either temporarily or permanently up to the full capacity of the system if their workload increases or an emergency requires it. More recently the system has added a metered usage capability. In this mode the full power of the system is always available to the customer (although they may administratively limit that). The usage is accumulated over a month and then the reported usage is submitted to Unisys billing. Depending on the specific contract terms the client may receive a bill for excess usage above some contracted baseline for the month or just a statement showing that the total contracted usage has been decremented. The first form is like a cell phone bill with the potential for charging for excess minutes. The latter is like buying a pre-paid phone card. File system OS 2200 does not have a hierarchical file system as do most other operating systems. Rather it has a structured naming convention and the notion of container files called program files. Files in OS 2200 are simply containers that may be addressed either by word offset in the file or by sector (28-word unit) offset in the file. The 28 words is a historical unit from an early mass storage device (the FASTRAND drum) that could hold 64 such units per physical track. Nonetheless, it is a fortunate historical accident. Four such 28-word units or 112 words occupy 504 bytes. With today's mass storage devices all using 512-byte physical records, OS 2200 clients have almost all adopted some multiple of 112 words as their physical record size and database page size. I/O processors automatically adjust for the 504<->512 byte mapping adding 8 bytes of zeros on writes and stripping them off on reads of each physical record. OS 2200 handles applications that use sizes other than multiples of 112 words by indivisibly reading the containing physical records and writing back out the unchanged and changed portions with data chaining. Special locking functions guarantee indivisibility even when there are device errors and across multiple systems in a cluster. File formats and other internal data structures are described in the Data Structures Programming Reference Manual. File names Ever since Exec-8, file names have taken the form: Qualifier*Filename(f-cycle) (e.g., "PERSONNEL*EMPLOYEES(+1)"). Qualifier and filename are simply twelve-character strings used to create whatever naming structure the client desires. F-cycle is a number from 0 to 999 that allows multiple generations of a file. These may be referenced by relative numbers: (+1) next or new cycle, (-1) previous cycle, (+0) current cycle. Leaving the cycle off defaults to the current cycle. Batch production runs that create new generations of files use this approach. The numbers wrap around after 999. Only 32 consecutive relative cycle numbers may exist at one time. Creating a (+1) deletes (-31). Any file may be used as a program file. A program file contains elements which generally act as files. Element naming is Qualifier*Filename(f-cycle).Element/version(e-cycle) (e.g., "PERSONNEL*PROGRAMS.TAXCALC/2008"). Element and version are twelve-character names used in any way a user desires. E-cycle is similar to f-cycle in that it represents a generation number but without the restriction to 32 concurrent cycles and the limit is 256K cycles. However, e-cycle only applies to text elements and each line in a text element is marked with the cycle numbers at which it was inserted and deleted. Elements also have a type and sub-type. The most commonly used types are "text" and "object." If the default type is not suitable, options select the appropriate type. Text elements also have sub-types that typically represent the programming language (e.g., "ASM", "C", "COB", "FOR"). The default element name of an object file is the same as the text file from which it was created. An object element may be executed if it is a main program or linked with other object elements including a main program. The linking may be static or dynamic. A main program may be executed without pre-linking provided all required sub-programs are in the same program file, are system libraries, or are otherwise known. Rules may be included in a program file to direct the dynamic linker's search for unfulfilled references. The linker may also be used to statically link multiple object modules together to form a new object module containing all instructions, data, and other information in the original object modules. Omnibus elements may be used as data by applications or may serve to hold structured information for applications and system utilities. There is no assumed structure to an omnibus element. For compatibility with earlier (basic mode) programming models, there are relocatable and absolute element types. Relocatable elements are the output of basic mode compilers. They may be combined by the basic mode static linker (@MAP – the collector) to form an "absolute" element which is executable. File management OS 2200 implements a fully virtual file system. Files may be allocated anywhere across any and all mass storage devices. Mass storage is treated as a large space pool similar to the way virtual memory is managed. While contiguous space is allocated if possible, mass storage is treated as a set of pages of 8KB size and a file can be placed in as many areas of the same or different devices as is required. Dynamic expansion of files attempts to allocate space adjacent to the previous allocation, but will find space wherever it is available. In fact, files need not even be present on mass storage to be used. The Exec and the file backup system are fully integrated. When file backups are made, the tape reel number(s) are recorded in the file directory. If space gets short on mass storage, some files are simply marked as "unloaded" if they have a current backup copy, and their space is available for use. If enough space can't be found that way, a backup is started. Any reference to an unloaded file will be queued while the file is copied back to mass storage. The whole system is automatic and generally transparent to users. Access methods In general, the Exec does not provide access methods. Files are simply containers. Access methods are provided by the language run time systems and the database manager. The one exception is a fixed-block access method provided for high-volume transaction processing. It has much less overhead than the database manager, but does participate in all locking, clustering, and recovery mechanisms. Removable packs When clients want more explicit control over the location of files, they can use the "removable pack" concept. At one time these truly represented physically removable disk packs, and the operating system would automatically generate pack mount requests to operators as needed. Today they are still used to place files, usually database files or transaction files, on one or more disk volumes. Files may still span multiple disk volumes, and now the list of volume names is given when the file is created. Files that are on such volume groups are still backed up but are not subject to automatic virtual space management. CIFS OS 2200 also provides a full implementation of the Common Internet File System (CIFS). CIFS implements the SMB protocol used by Microsoft servers and the UNIX/Linux Samba software. CIFS for ClearPath OS 2200 is both a file server and file client to other CIFS-compliant systems. This includes desktop PCs running Windows. CIFS supports SMB message signing. To maintain OS 2200 security, CIFS for ClearPath OS 2200 provides two levels of protection. First, OS 2200 files are not visible to the network until they have been declared as "shares" with a CIFS command. A specific privilege exists to control who may declare a share. The second level of control is that all access is still protected by OS 2200 security. Clients accessing OS 2200 via CIFS will either have to be automatically identified via NTLM or Kerberos or they will be presented with a query for their OS 2200 user id and password. CIFS allows OS 2200 files to be presented in a hierarchical view. Typically the qualifier will appear as the highest level in the tree followed by filename, element name, and version. In addition, files may be stored on OS 2200 servers using the full Windows filename format. Windows applications will see OS 2200 as another file server. OS 2200 applications have APIs available to read and write files existing on other CIFS-compliant servers, such as Windows file servers, in the network. Text files are automatically converted to and from OS 2200 internal formats. Binary files must be understood by the application program. The CIFSUT utility running under OS 2200 can exchange encrypted compressed files with other software, such as WinZip. Subsystems The concept of subsystems and protected subsystems are central to the design of OS 2200. A subsystem is most analogous to a .dll in Windows. It is code and data that may be shared among all programs running in the system. In OS 2200 each subsystem has its own set of banks that reside in a separate part of the address space that cannot be directly accessed by any user program. Instead the hardware and the OS provide a "gate" that may be the target of a Call instruction. See Unisys 2200 Series system architecture for more information. The database managers, run time libraries, messaging system, and many other system functions are implemented as subsystems. Some subsystems, usually consisting of pure code, such as the run time libraries, may be the direct target of a Call instruction without requiring a gate. These subsystems run in the user program's protection environment. Other subsystems, such as the database managers, consist of code and data or privileged code and may only be called via a gate. These subsystems may also have access control lists associated with them to control who may call them. More importantly, the gate controls the specific entry points that are visible, the protection environment in which the subsystem will run, and often a user-specific parameter that provides additional secure information about the caller. Security B1 security The OS 2200 security system is designed to protect data from unauthorized access, modification, or exposure. It includes an implementation of the DoD Orange Book B1 level specification. OS 2200 first obtained a successful B1 evaluation in September, 1989. That evaluation was maintained until 1994. After that point, OS 2200 developers continued to follow development and documentation practices required by the B1 evaluation. Central to a B1 system are the concepts of users and objects. Users have identities, clearance levels, compartments and privileges. Objects require certain combinations of those for various types of access. Objects in OS 2200 consist of files, protected subsystems, devices, and tape reels. The security profile of a user session includes the user identity, clearance level (0-63), compartment set, and set of allowed privileges. OS 2200 implements both Mandatory Access Control (MAC) and Discretionary Access Control (DAC) based on the Bell-La Padula model for confidentiality (no read up, no write down) and the Biba integrity model (no read down, no write up). For a run to read or execute a file, the run's executing clearance level must be greater than or equal to the clearance level of the file, and the file's clearance level must be 0 or within the clearance level range of the run; in addition, the run's executing compartment set must contain the file's compartment set. Because OS 2200 combines the Bell-La Padula and Biba model requirements, a run's executing clearance level and compartment set must exactly match those of a file to permit writing to the file or deleting it. DAC associates an access control list with an object; the list identifies users and user groups that have access and defines the type of access that user or group is allowed (read, write, execute, or delete). Because the full set of B1 controls is too restrictive for most environments, system administrators can configure servers by choosing which controls to apply. A set of security levels from Fundamental Security through Security Level 3 serves as a starting point. Security officer Every OS 2200 system has one user designated as the security officer. On systems configured with fundamental security, only the security officer is allowed to perform certain tasks. On systems configured with higher levels of security, other trusted users may be allowed to perform some of these tasks. OS 2200 provides a fine-grained security mechanism based on the principle of least privilege. This principle demands that only the minimum privilege be granted necessary to perform the task required. Thus, OS 2200 has no concept of a "Super User" role that can be assumed by any user. Rather it uses a large set of specific privileges which may be granted separately to each user. Each privilege is associated with a specific authority. File security On systems configured with security level 1 or higher levels, the user who creates an object is the object's owner. The default is that the object is private to the creating user, but it may also be public or controlled by an access control list. The owner or the security officer may create an access control list for that object. On system configured with fundamental security, files do not have owners. Instead, they are created private to an account or project, or they are public. Access to them can be controlled by read and write keys. Authentication When users log on to the system, they identify themselves and optionally select the clearance level and compartment set they will use for this session. OS 2200 offers a flexible authentication system. Multiple authentication mechanisms are supported concurrently. Client- or third party-written authentication software may also be used. Standard authentication capabilities include: User id and password maintained in an encrypted file by OS 2200 Authentication performed by an external system such as Microsoft Windows using its user id and password mechanism NTLM Kerberos LDAP The last two permit the use of biometrics, smart cards, and any other authentication mechanism supported by those technologies. Encryption OS 2200 provides encryption for data at rest through Cipher API, a software subsystem that encrypts and decrypts caller data. Cipher API also supports the use of a hardware accelerator card for bulk data encryption. For CMOS-based Dorado servers, CPComm provides SSL/TLS encryption for data in transit. For Intel-based Dorado servers, SSL and TLS are provided by openSSL, which is included in the Dorado firmware. All Dorado servers support TLS levels 1.0 through 1.2, as well as SSLv3, but SSL is disabled by default because of vulnerabilities in the protocol. Both CPComm and Cipher API use the encryption services of CryptoLib, a FIPS-certified software encryption module. The AES and Triple DES algorithms are among the algorithms implemented in CryptoLib. OS 2200 also supports encrypting tape drives, which provide encryption for archive data. Clustering OS 2200 systems may be clustered to achieve greater performance and availability than a single system. Up to 4 systems may be combined into a cluster sharing databases and files via shared disks. A hardware device, the XPC-L, provides coordination among the systems by providing a high-speed lock manager for database and file access. A clustered environment allows each system to have its own local files, databases, and application groups along with shared files and one or more shared application groups. Local files and databases are accessed only by a single system. Shared files and databases must be on disks that are simultaneously accessible from all systems in the cluster. The XPC-L provides a communication path among the systems for coordination of actions. It also provides a very fast lock engine. Connection to the XPC-L is via a special I/O processor that operates with extremely low latencies. The lock manager in the XPC-L provides all the functions required for both file and database locks. This includes deadlock detection and the ability to free up locks of failed applications. The XPC-L is implemented with two physical servers to create a fully redundant configuration. Maintenance, including loading new versions of the XPC-L firmware, may be performed on one of the servers while the other continues to run. Failures, including physical damage to one server, do not stop the cluster, as all information is kept in both servers. Operations and administration Operations OS 2200 operations is built around active operators and one or more consoles. Each console is a terminal window, part of which is reserved for a fixed display that is frequently updated with summary information about activity in the system. The rest of the console is used as a scrolling display of events. When a message is issued that requires an operator response, it is given a number from 0 to 9 and remains on the display until it is answered. Tape mount messages do scroll with other messages but will be repeated every two minutes until the tape is mounted. Operations Sentinel is used for all OS 2200 operations. OS 2200 consoles are simply windows within an Operations Sentinel display. There may be as many display PCs as desired. Remote operation is typical. Operations Sentinel supports any number of ClearPath, Windows, Linux, and UNIX systems. An auto-action message database is released with the product. This database allows Operations Sentinel to recognize messages. Scripts may be written to automatically respond to messages that require a response, hide unwanted messages, translate them to other languages, create events, etc. Full dark room operation is used by some clients. At most they will have Operations Sentinel displays at remote locations monitoring the system and creating alerts when certain events occur. Administration Administration of OS 2200 systems is performed using a wide variety of tools, each specialized to a particular area of the system. For example, there is a tool used for administering the transaction environment that allows new transaction programs to be installed, specifies all the necessary information about them, changes the queuing structure, priorities, and concurrency levels, and so on. Other tools are specific to the security officer and allow creation of users, changing allowed privileges, changing system security settings, etc.,, Most of the tools have a graphical interface although some do not. All provide a batch stored file interface where all actions are specified in the control stream. This allows scripting any and all of the administrative interfaces from either local sites, maybe based on time of day or other events, or from remote sites. Unique privileges are required for each administrative area. Application groups Application groups are a logical construct consisting of an instance of the Universal Data System (UDS), an instance of the message queue subsystem, and some set of transactions. Each application group has its own audit trail. OS 2200 supports a maximum of 16 application groups in a system. The notion of application group corresponds to what is often called "an application." That is, a set of programs and data that represent some larger unit of connected processing. For example, an application group might represent an airline system. Another application group might represent the corporate finance system. Or, application groups might represent instances of the same application and data models, as in bank branches. The important thing is that each application group has its own environment, sessions, recovery, etc. Application groups may be started, stopped, and recovered independently. Application groups do not have their own accounting and scheduling rules. Transactions in multiple application groups may share the same priorities and have interleaved priorities. This permits the site to control the relative priorities of transactions across the entire system. See also Unisys 2200 Series system architecture for information about the hardware architecture. Unisys OS 2200 programming languages for information about the OS 2200 compilers and linkers. Unisys OS 2200 databases for information about the OS 2200 databases and database manager. Unisys OS 2200 communications for information about OS 2200 communications. Unisys OS 2200 distributed processing for information about OS 2200 distributed processing. Other locations of source material The Unisys History Newsletter contains articles about Unisys history and computers. In addition to all of the Unisys History Newsletters there are links to other sites. Most of the historical archives of Unisys are at the Charles Babbage Institute at the University of Minnesota and at the Hagley Museum and Library in Delaware. The Charles Babbage Institute holds the archives from ERA, some early Remington Rand archives from Saint Paul, MN, and the Burroughs archives. The Hagley Museum and Library holds the bulk of the Sperry archives. References Footnotes Unisys operating systems

Operating System (OS)

Workplace OS Workplace OS is IBM's ultimate operating system prototype of the 1990s. It is the product of an exploratory research program in 1991 which yielded a design called the Grand Unifying Theory of Systems (GUTS), proposing to unify the world's systems as generalized personalities cohabitating concurrently upon a universally sophisticated platform of object-oriented frameworks upon one microkernel. Developed in collaboration with Taligent and its Pink operating system imported from Apple via the AIM alliance, the ambitious Workplace OS was intended to improve software portability and maintenance costs by aggressively recruiting all operating system vendors to convert into Workplace OS personalities. In 1995, IBM reported that "Nearly 20 corporations, universities, and research institutes worldwide have licensed the microkernel, laying the foundation for a completely open microkernel standard." At the core of IBM's new unified strategic direction for the entire company, the project was intended also as a bellwether toward PowerPC hardware platforms, to compete with the Wintel duopoly. With protracted development spanning four years and $2 billion (or 0.6% of IBM's revenue for that period), the project suffered development hell characterized by workplace politics, feature creep, and the second-system effect. Many idealistic key assumptions made by IBM architects about software complexity and system performance were never tested until far too late in development, and found to be infeasible. In January 1996, the first and only commercial preview was launched with the name "OS/2 Warp Connect (PowerPC Edition)" by limited special order by select IBM customers, as a crippled product. The entire operating system was soon discontinued in 1996 due to very low market demand, including that of enterprise PowerPC hardware. A University of California case study described the Workplace OS project as "one of the most significant operating systems software investments of all time" and "one of the largest operating system failures in modern times". Overview Objective By 1990, IBM acknowledged the software industry to be in a state of perpetual crisis. This was due to the chaos from inordinate complexity of software engineering inherited by its legacy of procedural programming practices since the 1960s. Large software projects were too difficult, fragile, expensive, and time-consuming to create and maintain; they required too many programmers, who were too busy with fixing bugs and adding incremental features to create new applications. Different operating systems were alien to each other, with their own proprietary applications. IBM envisioned "life after maximum entropy" through "operating systems unification at last" and wanted to lay a new worldview for the future of computing. IBM sought a new world view of a unified foundation for computing, based upon the efficient reuse of common work. It wanted to break the traditional monolithic software development cycle of producing alphas, then betas, then testing, and repeating over the entire operating system — instead, compartmentalizing the development and quality assurance of individual unit objects. This new theory of unifying existing legacy software and the new way of building all new software, was nicknamed the Grand Unified Theory of Systems or GUTS. Coincidentally, Apple already had a two-year-old secret prototype of its microkernel-based object-oriented operating system with application frameworks, named Pink. The theory of GUTS was expanded by Pink, yielding Workplace OS. Architecture IBM described its new microkernel architecture as scalable, modular, portable, client/server distributed, and open and fully licensable both in binary and source code forms. This microkernel-based unified architecture was intended to allow all software to become scalable both upward into supercomputing space and downward into mobile and embedded space. Leveraged upon a single microkernel, IBM wanted to achieve its grand goal of unification by simplifying complex development models into reusable objects and frameworks, and all while retaining complete backward compatibility with legacy and heritage systems. Multiple-library support would allow developers to progressively migrate select source code objects to 64-bit mode, with side-by-side selectable 32-bit and 64-bit modes. IBM's book on Workplace OS says, "Maybe we can get to a 64-bit operating system in our lifetime." IBM intended shareable objects to eventually reduce the footprint of each personality, scaling them down to a handheld computing profile. At the base of Workplace OS is a fork of the Mach 3.0 microkernel (release mk68) originally developed by Carnegie Mellon University and heavily modified by the Open Software Foundation's Research Institute. Officially named "IBM Microkernel", it provides five core features: IPC, virtual memory support, processes and threads, host and processor sets, and I/O and interrupt support. On top of the IBM Microkernel, is a layer of shared services (originally called Personality Neutral Services or PNS) to cater to some or all of the personalities above them. Shared services are endian-neutral, have no user interface, and can serve other shared services. Byte summarizes that shared services "can include not only low-level file system and device-driver services but also higher-level networking and even database services. [Workplace OS's lead architect Paul Giangarra] believes that locating such application-oriented services close to the microkernel will improve their efficiency by reducing the number of function calls and enabling the service to integrate its own device drivers." This layer contains the file systems, the scheduler, network services, and security services. IBM first attempted a device driver model completely based in userspace to maximize its dynamic configuration, but later found the need to blend it between userspace and kernelspace, while keeping as much as possible in userspace. The Adaptive Driver Architecture (ADD) was designed for the creation of layered device drivers, which are easily portable to other hardware and operating system platforms beyond Workplace OS, and which consist of about 5000-8000 lines of device-specific code each. Some shared services are common only to select personalities, such as MMPM serving multimedia only to Windows 3.1 and OS/2 personalities, and which is alien or redundant to other markets. Atop the shared services, another layer of userspace servers called personalities provide DOS, Windows, OS/2 (Workplace OS/2), and UNIX (WPIX) environments. The further hope was to support OS/400, AIX, Taligent OS, and MacOS personalities. Personalities provide environment subsystems to applications. Any one personality can be made dominant for a given version of the OS, providing the desktop user with a single GUI environment to accommodate the secondary personalities. In 1993, IBM intended one release version to be based upon the OS/2 Workplace Shell and another to be based upon the UNIX Common Desktop Environment (CDE). IBM explained the branding: "Workplace OS is the codename for a collection of operating system components including, among others, the IBM Microkernel and the OS/2 personality. Workplace OS/2 is the specific codename for the OS/2 personality. Workplace OS/2 will operate with the IBM Microkernel and can be considered OS/2 for the PowerPC." For the 1995 final preview release, IBM continued, "When we stopped using the name 'Workplace' and started calling the product 'OS/2 for the PowerPC', you might have thought that the 'Workplace' was dead. But the 'Workplace' is far from dead. It has simply been renamed for prime time." IBM intended for Workplace OS to run on several processor architectures, including PowerPC, ARM, and x86 which would range in size from handheld PDAs to workstations to large 64-bit servers and supercomputers. IBM saw the easy portability of the Workplace OS as creating a simple migration path to move its existing x86 (DOS and OS/2) customer base onto a new wave of standard reference PowerPC-based systems, such as the PC Power Series and the Power Macintosh. Creating a unique but open and industry-standard reference platform of open-source microkernel, IBM hedged its company-wide operating system strategy by aggressively attempting to recruit other computer companies to adopt its microkernel as a basis for their own operating systems. History Development GUTS In January 1991, there was an internal presentation to the IBM Management Committee of a new strategy for operating system products. This included a chart called the Grand Unification Theory of Operating Systems (GUTS) which outlined how a single microkernel underlying common subsystems could provide a single unifying architecture for the world's many existing and future operating systems. It was initially based in a procedural programming model, not object-oriented. The design elements of this plan had already been implemented on IBM's RS/6000 platform via the System Object Model (SOM), a model which had already been delivered as integral to the OS/2 operating system. Sometime later in 1991, as a result of the Apple/IBM business partnership, a small exploratory IBM team first visited the Taligent team, who demonstrated a relatively mature prototype operating system and programming model based entirely on Apple's Pink project from 1987. There, GUTS's goals were greatly impacted and expanded by exposure to these similar goals—especially advanced in the areas of aggressive object-orientation, and of software frameworks upon a microkernel. IBM's optimistic team saw the Pink platform as being the current state of the art of operating system architecture. IBM wanted to adopt Pink's more object-oriented programming model and framework-based system design, and add compatibility with legacy procedural programming along with the major concept of multiple personalities of operating systems, to create the ultimate possible GUTS model. Through the historic Apple/IBM partnership, Apple's CEO John Sculley said that the already volume-shipping OS/2 and MacOS would become unified upon the common PowerPC hardware platform to "bring a renaissance to the industry". In late 1991, a small team from Boca Raton and Austin began implementing the GUTS project, with the goal of proving the GUTS concept, by first converting the monolithic OS/2 2.1 system to the Mach microkernel, and yielding a demo. To gain shared access to key personnel currently working on the existing OS/2, they disguised the project as the Joint Design Task Force and brought "a significant number" of personnel from Boca, Austin (with LANs and performance), Raleigh (with SNA and other transport services), IBM Research (with operating systems and performance), and Rochester (with the 64-bit, object-oriented worldview from AS/400). Pleased with the robust, long-term mentality of the microkernel technology and with the progress of the project, the team produced a prototype in mid 1992. The initial internal-development prototypes ran on x86-based hardware and provided a BSD Unix derived personality and a DOS personality. Demos and business reorganization At Comdex in late 1992, the team flew in and assembled a private demonstration based on last-minute downloads to replace corrupted files and one hour of sleep. The presentation was so well received that the prototype was put on the trade show floor on Thursday, as the first public demonstration of the IBM Microkernel-based system running OS/2, DOS, 16-bit Windows, and UNIX applications. In 1992, IBM ordered Taligent to migrate the Taligent OS from its internally developed microkernel named Opus, onto the IBM Microkernel. Ostensibly, this would have allowed Taligent's operating system (implemented as a Workplace OS personality) to execute side-by-side with DOS and OS/2 operating system personalities. In 1993, InfoWorld reported that Jim Cannavino "has gone around the company and developer support for a plan to merge all of the company's computing platforms—ES/9000, AS/400, RS/6000, and PS/2—around a single set of technologies, namely the PowerPC microprocessor, the Workplace OS operating system, and the Taligent object model, along with a series of open standards for cross-platform development, network interoperability, etc." On June 30, 1993, a presentation was given at the Boca Programming Center by Larry Loucks, IBM Fellow and VP of Software Architecture of the Personal Software Products (PSP) Division. By 1993, IBM reportedly planned two packages of Workplace OS, based on personality dominance: one based on the OS/2 Workplace Shell and another based upon the UNIX Common Desktop Environment (CDE). IBM and Apple were speaking about the possibility of a Mac OS personality. By January 1994, the IBM Power Personal Systems Division had still not yet begun testing its PowerPC hardware with any of its three intended launch operating systems: definitely AIX and Windows NT, and hopefully also Workplace OS. Software demonstrations showed limited personality support, with the dominant one being the OS/2 Workplace Shell desktop, and the DOS and UNIX personalities achieving only fullscreen text mode support with crude hotkey switching between the environments. Byte reported that the multiple personality support promised in Workplace OS's conceptual ambitions was more straightforward, foundational, and robust than that of the already-shipping Windows NT. The magazine said "IBM is pursuing multiple personalities, while Microsoft appears to be discarding them" while conceding that "it's easier to create a robust plan than a working operating system with robust implementations of multiple personalities". In 1994, the industry was reportedly shifting away from monolithic development and even application suites, toward object-oriented, component-based, crossplatform, application frameworks. By 1995, Workplace OS was becoming notable for its many and repeated launch delays, with IBM described as being inconsistent and "wishy washy" with dates. This left IBM's own PowerPC hardware products without a mainstream operating system, forcing the company to at least consider the rival Windows NT. In April 1994, Byte reported that under lead architect Paul Giangarra, IBM had staffed more than "400 people working to bring [Workplace OS] up on Power Personal hardware". In May 1994, the RISC Systems software division publicly announced the company's first attempt to even study the feasibility of converting AIX into a Workplace OS personality, which the company had been publicly promising since the beginning. One IBM Research Fellow led a team of fewer than ten, to identify and address the problem, which was the fundamentally incompatible byte ordering between the big-endian AIX and the little-endian Workplace OS. This problem is endemic, because though the PowerPC CPU and Workplace OS can perform in either mode, endianness is a systemwide configuration set once at boot time only; and Workplace OS favors OS/2 which comes from the little-endian Intel x86 architecture. After seven months of silence on the issue, IBM announced in January 1995 that the intractable endianness problem had resulted in the total abandonment of the flagship plan for an AIX personality. In late 1994, as Workplace OS approached its first beta version, IBM referred to the beta product as "OS/2 for the PowerPC". As the project's first deliverable product, this first beta was released to select developers on the Power Series 440 in December 1994. There was a second beta release in 1995. By 1995, IBM had shipped two different releases of an application sampler CD, for use with the beta OS releases. Preview launch In mid 1995, IBM officially named its planned initial Workplace OS release "OS/2 Warp Connect (PowerPC Edition)" with the code name "Falcon". In October 1995, IBM announced the upcoming first release, though still a developer preview. The announcement predicted it to have version 1.0 of the IBM Microkernel with the OS/2 personality and a new UNIX personality, on PowerPC. Having been part of the earliest demonstrations, the UNIX personality was now intended to be offered to customers as a holdover due to the nonexistence of a long-awaited AIX personality, but the UNIX personality was also abandoned prior to release. This developer release is the first ever publication of Workplace OS, and of the IBM Microkernel (at version 1.0), which IBM's internal developers had been running privately on Intel and PowerPC hardware. The gold master was produced on December 15, 1995 with availability on January 5, 1996, only to existing Power Series hardware customers who paid $215 for a special product request through their IBM representative, who then relayed the request to the Austin research laboratory. The software essentially appears to the user as the visually identical and source-compatible PowerPC equivalent of the mainstream OS/2 3.0 for Intel. Packaged as two CDs with no box, its accompanying overview paper booklet calls it the "final edition" but it is still a very incomplete product intended only for developers. Its installer only supports two computer models, the IBM PC Power Series 830 and 850 which have PowerPC 604 CPUs of , of RAM, and IDE drives. Contrary to the product's "Connect" name, the installed operating system has no networking support. However, full networking functionality is described within the installed documentation files, and in the related book IBM's Official OS/2 Warp Connect PowerPC Edition: Operating in the New Frontier (1995) — all of which the product's paper booklet warns the user to disregard. The kernel dumps debugging data to the serial console. The system hosts no compiler, so developers are required to cross-compile applications on the source-compatible OS/2 for Intel system, using MetaWare’s High C compiler or VisualAge C++, and manually copy the files via relocatable medium to run them. With an officially concessionary attitude, IBM had no official plans for a general release packaged for OEMs or retail, beyond this developer preview available only via special order from the development lab. Upon its launch, Joe Stunkard, spokesman for IBM's Personal Systems Products division, said "When and if the Power market increases, we'll increase the operating system's presence as required." On January 26, 1996, an Internet forum statement is made by John Soyring, IBM's Vice President of Personal Software Products: "We are not planning additional releases of the OS/2 Warp family on the PowerPC platform during 1996 — as we just released in late December 1995 the OS/2 Warp (PowerPC Edition) product. ... We have just not announced future releases on the PowerPC platform. In no way should our announcement imply that we are backing away from the PowerPC." Roadmap On November 22, 1995, IBM's developer newsletter said, "Another focus of the 1996 product strategy will be the IBM Microkernel and microkernel-based versions of OS/2 Warp. Nearly 20 corporations, universities, and research institutes worldwide have licensed the microkernel, laying the foundation for a completely open microkernel standard." IBM planned a second feature-parity release for Intel and PowerPC in 1996. In 1996, a Workplace OS version was rumored to exist internally that also supported x86 and ARM processors. IBM reportedly tested OS/2 on the never-released x86-compatible PowerPC 615 CPU. At this point, the several-year future roadmap of Workplace OS included IBM Microkernel 2.0 and was intended to subsume the fully converged future of the OS/2 platform starting after the future release of OS/2 version 4, including ports to Pentium, Pentium Pro, MIPS, ARM, and Alpha CPUs. Discontinuation The Workplace OS project was finally canceled in March 1996 due to myriad factors: inadequate performance; low acceptance of the PowerPC Reference Platform; poor quality of the PowerPC 620 launch; extensive cost overruns; lack of AIX, Windows, or OS/400 personalities; and the overall low customer demand. The only mainstream desktop operating system running on PowerPC was Windows NT, which also lacked supply and demand. Industry analysts said that "the industry may have passed by the PowerPC". In 1996, IBM also closed the Power Personal Division responsible for personal PowerPC systems. IBM stopped developing new operating systems, and instead committed heavily to Linux, Java, and some Windows. In 2012, IBM described Linux as the "universal platform" in a way that happens to coincide with many of the essential design objectives of GUTS. Reception Industrial reception Reception was enthusiastically but skeptically mixed, as the young IT industry was already constantly grappling with the second-system effect, and was now presented with Workplace OS and PowerPC hardware as the ultimate second system duo to unify all preceding and future systems. On November 15, 1993, InfoWorlds concerns resembled the Osborne effect: "Now IBM needs to talk about this transition without also telling its customers to stop buying all the products it is already selling. Tough problem. Very little of the new platform that IBM is developing will be ready for mission-critical deployment until 1995 or 1996. So the company has to dance hard for two and maybe three years to keep already disaffected customers on board." In 1994, an extensive analysis by Byte reported that the multiple personality concept in Workplace OS's beta design was more straightforward, foundational, and robust than that of the already-shipping Windows NT. The magazine said "IBM is pursuing multiple personalities, while Microsoft appears to be discarding them" while conceding that "it's easier to create a robust plan than a working operating system with robust implementations of multiple personalities". Upon the January 1996 developer final release, InfoWorld relayed the industry's dismay that the preceding two years of delays had made the platform "too little, too late", "stillborn", and effectively immediately discontinued. An analyst was quoted, "The customer base would not accept OS/2 and the PowerPC at the same time" because by the time IBM would eventually ship a final retail package of OS/2 on PowerPC machines, "the power/price ratio of the PowerPC processor just wasn't good enough to make customers accept all of the other drawbacks" of migrating to a new operating system alone. In 2013, Ars Technica retrospectively characterized the years of hype surrounding Workplace OS as supposedly being "the ultimate operating system, the OS to end all OSes ... It would run on every processor architecture under the sun, but it would mostly showcase the power of POWER. It would be all-singing and all-dancing." Internal analysis In January 1995, four years after the conception and one year before the cancellation of Workplace OS, IBM announced the results of a very late stage analysis of the project's initial assumptions. This concluded that it is impossible to unify the inherent disparity in endianness between different proposed personalities of legacy systems, resulting in the total abandonment of the flagship plan for an AIX personality. In May 1997, one year after its cancellation, one of its architects reflected back on the intractable problems of the project's software design and the limits of available hardware. Academic analysis In September 1997, a case study of the history of the development of Workplace OS was published by the University of California with key details having been verified by IBM personnel. These researchers concluded that IBM had relied throughout the project's history upon multiple false assumptions and overly grandiose ambitions, and had failed to apprehend the inherent difficulty of implementing a kernel with multiple personalities. IBM considered the system mainly as its constituent components and not as a whole, in terms of system performance, system design, and corporate personnel organization. IBM had not properly researched and proven the concept of generalizing all these operating system personalities before starting the project, or at any responsible timeframe during it — especially its own flagship AIX. IBM assumed that all the resultant performance issues would be mitigated by eventual deployment upon PowerPC hardware. The Workplace OS product suffered the second-system effect, including feature creep, with thousands of global contributing engineers across many disparate business units nationwide. The Workplace OS project had spent four years and $2 billion (or 0.6% of IBM's revenue for that period), which the report described as "one of the most significant operating systems software investments of all time" and "one of the largest operating system failures in modern times". See also Taligent, sister project of Workplace OS IBM Future Systems project, a previous grand unifying project Copland, another second system prototype from Apple 64DD, Nintendo's ambitious 1990s platform known for extreme repeated lateness and commercial failure Notes References Further reading OS/2 PowerPC Toolkit, Developer Connection CD-ROMs. The first doc is a description of the OS/2 ABI on PowerPC32. The second is an API addendum, including a description of new 32-bit console APIs. ARM operating systems IBM operating systems Mach (kernel) Microkernel-based operating systems OS/2 PowerPC operating systems X86 operating systems Microkernels

Operating System (OS)

Windows (disambiguation) Microsoft Windows is an operating system developed by Microsoft. Windows may also refer to: The plural of window, an opening in an opaque surface through which light can pass Computing X Window System, often erroneously referred to as X Windows, the basis for many graphical user interfaces on a variety of operating systems including many Unix and Linux variants OpenWindows, the X Window System implementation for Solaris from 1989 to 2002 DECwindows, the X Window System implementation used by Digital Equipment Corporation Window (computing), a display rectangle used by a graphical user interface (GUI) Windows key, a key on computer keyboards Arts and entertainment Film and television Windows (film), a 1980 erotic thriller. Windows (TV series), an American anthology series. Music Windows (country-psych band), Los Angeles based band founded in 2018 Windows (jazz band), a smooth jazz band (1984–1996) Windows (composition), a 1966 jazz standard by Chick Corea "Windows", a 1982 song on Vinyl Confessions by Kansas Windows (Jon Lord album), 1974 Windows (Lee Konitz and Hal Galper album), 1975 Windows (O'Donel Levy album), 1976 Windows (Charlie Daniels album), 1982 Windows (Amanda Somerville album), 2008 See also Window (disambiguation) Windowing (disambiguation) Win-OS/2

Operating System (OS)

Windows Me Windows Millennium Edition, or Windows Me (marketed with the pronunciation of the pronoun "me"), is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It is the successor to Windows 98, and was released to manufacturing on June 19, 2000, and then to retail on September 14, 2000. It was Microsoft's main operating system for home users until the introduction of its successor Windows XP in 2001. Windows Me was targeted specifically at home PC users, and included Internet Explorer 5.5 (later default was Internet Explorer 6), Windows Media Player 7 (later default was Windows Media Player 9 Series) and the new Windows Movie Maker software, which provided basic video editing and was designed to be easy to use for consumers. Microsoft also incorporated features first introduced in Windows 2000, which had been released as a business-oriented operating system seven months earlier, into the graphical user interface, shell and Windows Explorer. Although Windows Me was still ultimately based around MS-DOS like its predecessors, access to real-mode DOS was restricted to decrease system boot time. Windows Me was initially positively received, but it soon garnered a negative reception from users due to stability issues, and is now viewed by many as one of the worst operating systems Microsoft has ever produced. In October 2001, Windows XP was released to the public, having already been under development at the time of Windows Me's release, and popularized most of Windows Me's features, while being far more stable. After the introduction of Windows XP, mainstream support for Windows Me ended on December 31, 2003, followed by extended support on July 11, 2006. Development At the 1998 Windows Hardware Engineering Conference, Microsoft CEO Bill Gates stated that Windows 98 would be the last iteration of Windows to use the Windows 9x kernel, with the intention for the next consumer-focused version to be based on the NT kernel, unifying the two branches of Windows. However, it soon became apparent that the development work involved was too great to meet the aim of releasing before the end of 2000, particularly given the ongoing parallel work on the eventually-canceled Microsoft Neptune project. The Consumer Windows development team was therefore re-tasked with improving Windows 98 while porting some of the look-and-feel from Windows 2000. Microsoft President Steve Ballmer publicly announced these changes at the next Windows HEIC in 1999. On July 23, 1999, the first alpha version of Windows Me was released to testers. Called Development Preview 1, it was very similar to Windows 98 SE, with a very early iteration of the new Help and Support feature as the only major change. Three more Development Previews were released over the subsequent two months. The first beta version was released to testers and the industry press on September 24, 1999, with the second coming on November 24 that year. Beta 2 showed the first real changes from Windows 98, including importing much of the look-and-feel from Windows 2000, and the removal of real-mode DOS. Industry expert Paul Thurrott reviewed Beta 2 upon release and spoke positively of it in a review. By early 2000, Windows Me was reportedly behind schedule, and an interim build containing the new automatic update feature was released to allay concerns about a delayed-release. Beta 3 was released on April 11, 2000, and this version marked the first appearance of its final startup and shutdown sounds derived from Windows 2000, as the previous betas used Windows 98's startup and shutdown sounds. Although Microsoft signed off on the final build of Windows Me on June 28, 2000, after trialing three Release Candidate builds with testers, the final retail release was pushed back to September 14 for reasons that were not clear. Shortly after Windows Me was released to manufacturing on June 19, 2000, Microsoft launched a marketing campaign to promote it in the U.S., which they dubbed the Meet Me Tour. A national partnered promotional program featured the new OS, OEMs and other partners in an interactive multimedia attraction in 25 cities. Windows Me was released for retail sale on September 14, 2000. At launch time, Microsoft announced a time-limited promotion from September 2000 to January 2001 which entitled Windows 98 and Windows 98 SE users to upgrade to Windows Me for $59.95 instead of the regular retail upgrade price of $109. Non-upgrade versions cost $209, the same as Windows 98 on its release. New and updated features User interface Windows Me featured the shell enhancements inherited from Windows 2000 such as personalized menus, customizable Windows Explorer toolbars, auto-complete in Windows Explorer address bar and Run box, Windows 2000 advanced file type association features, displaying comments in shortcuts as tooltips, extensible columns in Details view (IColumnProvider interface), icon overlays, integrated search pane in Windows Explorer, sort by name function for menus, Places bar in common dialogs for Open and Save, cascading Start menu special folders, some Plus! 95 and Plus! 98 themes, and updated graphics. The notification area in Windows Me and later supported 16-bit high color icons. The Multimedia control panel was also updated from Windows 98. Taskbar and Start Menu options allowed disabling of the drag and drop feature and could prevent moving or resizing the taskbar, which was easier for new users. Hardware support improvements Faster boot times: Windows Me features numerous improvements for improving cold boot time, pre and post-logon boot times and time required for resuming from hibernation. Processing of real mode configuration files, CONFIG.SYS and AUTOEXEC.BAT, is bypassed at startup and essential real mode drivers like HIMEM.SYS and SMARTDRV.EXE are embedded into IO.SYS. The registry is loaded only once; for efficient loading, the registry is split into three files instead of two (SYSTEM.DAT and USER.DAT), with the new file CLASSES.DAT containing the contents of the hive HKEY_CLASSES_ROOT required for boot loaded initially. Plug and Play device enumeration is more parallelized than in Windows 98. Boot time is not affected due to unavailability of a DHCP server or other network components. There are also optimizations to prevent boot slowdown due to BIOS POST operations. USB Human Interface Device Class: Generic support for 5-button mice is also included as standard and installing IntelliPoint allows reassigning the programmable buttons. Windows Image Acquisition: Windows Me introduced the Windows Image Acquisition API for a standardized method of allowing Windows applications to transparently and more easily communicate with image acquisition devices, such as digital cameras and scanners. WIA intended to improve the configuration and the user interface for interacting with scanners and such devices, (which were previously supported by the TWAIN standard) and simplify writing device drivers for developers. WIA also includes support for USB still image capture device classes such as scanners and cameras through the Picture Transfer Protocol. Improved power management and suspend/resume operations: The OEM version of Windows Me supports OS-controlled ACPI S4 sleep state (hibernation) and other power management features without manufacturer-supplied drivers. USB and FireWire support improvements: Windows Me is the only operating system in the Windows 9x series that includes generic drivers for USB mass storage devices and USB printers. Support for FireWire SBP-2 scanners and storage devices is also improved. The , DirectSound, and DirectShow APIs support non-PCM formats such as AC-3 or WMA over S/PDIF. Digital media Windows Movie Maker: This utility is based on DirectShow and Windows Media technologies to provide Microsoft Windows computer systems with basic video capture and edit capabilities. It provides users with the ability to capture, edit, and re-encode media content into the Windows Media format, a tightly compressed format that requires a minimal amount of storage space on the computer's hard disk when compared to many other media formats. Windows Media Player 7: The new version of the Windows multimedia player software introduces jukebox functionality featuring the Media Library, support for CD burning, an integrated media encoder, and the ability to transfer music directly to portable devices. Another new feature is its radio tuner that can be used to search for and connect to radio stations over the internet. Users can also customize the look and feel of the user interface through interactive skins. Windows DVD Player: The software DVD player in Windows Me is a redesigned version of the one featured in Windows 98 which, unlike its predecessor, does not require a dedicated decoder card for DVD playback. Instead, it supports software decoding through a third-party decoder. Networking technologies Net Crawler: Windows Me introduced a net crawling feature which automatically searches out and creates shortcuts to network shares and printers in My Network Places. This can be controlled using the Automatically search for network folders and printers option. Shortcuts that are added by the net crawler but not detected again on the network in a reasonable time period are aged out and deleted. New TCP/IP Stack: Windows Me includes the Windows 2000 networking stack and architecture. The Home Networking Wizard is designed to help users to set up a computer that is running Windows Me for use on a small home network. This includes setting up Internet Connection Sharing (ICS) on a computer running Windows Me so the computer can share a connection to the Internet with other computers on the home network. Dial-up Networking component was updated in Windows Me and provides several enhancements while maintaining the desired features of prior releases of the operating system. The user interface had been reworked to provide all configurable parameters in one convenient location. The user interface now included three new tabs: Networking, Security and Dialing. To improve dial-up networking, Windows Me includes built-in support for the Connection Manager dial-up client. Using the Connection Manager Administration Kit (an optional networking component in Windows 2000 Server), network administrators can pre-configure and deploy dial-up networking connections, by means of a Connection Manager service profile, to Windows Me–based client machines. Network Driver Interface Specification (NDIS) version 5.0 for Windows Me was enhanced to provide programming interface parity with NDIS version 5.0 in Windows 2000. This means that the programming interfaces that the author of a network device driver uses are the same for both of these Windows platforms. Universal Plug and Play: Windows Me introduced support for Universal Plug and Play (UPnP). Universal Plug and Play and NAT traversal APIs can also be installed on Windows 98 and Windows 98 SE by installing the Windows XP Network Setup Wizard. System utilities System Restore: Windows Me introduced the "System Restore" logging and reversion system, which was meant to simplify troubleshooting and solve problems. It was intended to work as a rollback and recovery feature so that if the installation of an application or a driver adversely affected the system, the user could undo the installation and return the system to a previously working state. It does this by monitoring changes to Windows system files and the registry. System Restore protects only the operating system files, not documents, and therefore is not a substitute for a backup program. System File Protection: First introduced with Windows 2000 (as Windows File Protection), and expanding on the capabilities introduced with System File Checker in Windows 98, System File Protection aimed to protect system files from modification and corruption silently and automatically. When the file protection is in effect, replacing or deleting a system file causes Windows Me to silently restore the original copy. The original is taken from a hard drive backup folder (%WinDir%\Options\Install) or from the Windows Me installation CD, if the cached copy of files on the hard disk has been deleted. If no installation CD is in the drive, a dialog box alerts the user about the problem and requests that the CD be inserted. System File Protection is a different technology from System Restore and should not be confused with the latter. System Restore maintains a broad set of changed files including added applications and user configuration data stored repeatedly at specific points in time restored by the user, whereas System File Protection protects operating system files with no user input. System Configuration Utility allows users to manually extract and restore individual system files from the Windows Me setup files. It has also been updated with three new tabs called "Static VxDs", "Environment" and "International". The Static VxDs tab allows users to enable or disable static virtual device drivers to be loaded at startup, the Environment tab allows users to enable or disable environment variables, and the International tab allows users to set international language keyboard layout settings that were formerly set via the real mode MS-DOS configuration files. A Cleanup button on the Startup tab allows cleaning up invalid or deleted startup entries. System Monitor has been updated with a Dial-Up Adapter section. Users can now monitor items such as Connection Speeds, Bytes Received or Transmitted / Second. SCANDISK runs from within Windows upon an improper shutdown before the Windows Shell loads. Automatic Updates: The Automatic Updates utility automatically downloads and installs critical updates from the Windows Update Web site with little user interaction. It is set up to check Windows Update once every 24 hours by default. Users can choose to download which update they want, although high-priority updates must be downloaded and installed. Compressed Folders: Windows Me includes native support for ZIP files through the 'Compressed Folders' Explorer extension. This extension was originally introduced in the Plus! 98 collection for Windows 98, but is included in the base operating system in Windows Me. A new Help and Support program has also been added, replacing the HTML Help-based documentation in Windows 2000 and Windows 98. The Help and Support Center is entirely HTML-based and takes advantage of a technology called Support Automation Framework (SAF), that can show support information from the internet, allows collecting data for troubleshooting via WMI and scripting and for third parties to plug into Windows Help and Support. Several other support tools also shipped with Windows Me. Windows Me also includes Internet Explorer 5.5, which supports a new Print Preview feature. It also shipped with the MSN Messenger Service. Accessibility features On-Screen Keyboard: Originally introduced with Windows 2000, On-Screen Keyboard makes it possible to input characters using the mouse instead of the keyboard. The Mouse Control Panel incorporates IntelliPoint features, namely ClickLock (selecting or dragging without continuously holding down the mouse button), hiding the pointer while typing, and showing it by pressing Ctrl. The cursor (system caret) can be set to a thicker width. Increased Active Accessibility support in utilities such as Calculator and Magnifier. Removed features Real mode DOS Windows Me restricted support for real mode MS-DOS. As a result, IO.SYS in Windows Me disregards CONFIG.SYS, COMMAND.COM and WIN.COM and directly executes VMM32.VXD. In its default configuration the system would neither boot into an MS-DOS command prompt nor exit to DOS from Windows; real mode drivers such as ANSI.SYS could not be loaded and older applications that require real mode could not be run. Microsoft argued that the change improved the speed and reliability of the boot process. In Windows Me, the CONFIG.SYS and AUTOEXEC.BAT files are used only to set global environment variables. The two files (if present) are scanned for settings relating to the environment variables, and any other commands present are moved into a Windows registry key (see below). The two files thus contain only settings and preferences which configure the "global environment" for the computer during the boot phase or when starting a new virtual DOS machine (VDM). To specify or edit other startup values (which, in Windows 98, would be present in the AUTOEXEC.BAT file) the user must edit the following Windows registry key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\SessionManager\Environment For troubleshooting and crash recovery, both the Windows Me CD-ROM and the Windows Me startup disk (a user-creatable floppy disk, known as the Emergency Boot Disk (EBD)) allowed booting into real mode MS-DOS. It is possible to restore real mode DOS functionality through various unofficial means. Additionally, a registry setting exists that re-enables the "Restart in MS-DOS mode" option in the shutdown dialog box; however, unless patched unofficially with third-party software, Windows Me cannot be booted to MS-DOS real mode. Other components Unlike past versions of Windows 9x, Windows Me was entirely aimed at home users, and thus had certain enterprise-oriented features removed. Several features of its predecessors did not work or were officially unsupported by Microsoft on Windows Me, including Automated Installation, Active Directory client services, System Policy Editor, Personal Web Server and ASP. These features were supported on its predecessors, Windows 98 and Windows 95. A Resource Kit publication, targeted towards system administrators, was never published for Windows Me. Other features that were removed or never updated to work with Windows Me included Microsoft Fax, QuickView and DriveSpace, as well as the GUI FAT32 conversion tool. Several Windows Explorer commands were also modified in Windows Me, matching the menu structure in Windows 2000. While some were simply moved to a different location, certain functionality of the Go menu, as well as the Find command on the Tools menu, are no longer available. For the latter change Microsoft recommends using a variety of similar functionality labeled Search. Upgradeability Windows Me could have its components upgraded or have new components installed up to the latest versions: Internet Explorer 6 SP1 and Outlook Express 6 SP1 Windows Media Format Runtime and Windows Media Player 9 Series (including Windows Media Encoder 7.1 and the Windows Media 8 Decoding Utility) MSN Messenger 7.0 Windows Installer 2.0 DirectX 9.0c (the latest compatible runtime is from October 2007.) Microsoft .NET Framework up to and including version 2.0 (2.0 SP1 and higher versions are not supported.) Microsoft Visual C++ 2005 runtime Text Services Framework Several other components such as MSXML 3.0 SP7, Microsoft Agent 2.0, NetMeeting 3.01, MSAA 2.0, ActiveSync 3.8, WSH 5.6, Microsoft Data Access Components 2.81 SP1, WMI 1.5 and Speech API 4.0. Office XP was the last version of Microsoft Office to be compatible with Windows Me. The Microsoft Layer for Unicode can be installed to allow certain Unicode applications to run on the operating system. System requirements Windows Me is only designed to handle up to 512 MB of RAM by default. Systems with larger RAM pools may lose stability; however, depending on the hardware and software configuration, it is sometimes possible to manually tweak the installation to continue working with somewhat larger amounts of RAM as well. Systems with 1.5 GB of RAM or more may reboot continuously during startup. The /nm setup switch can be used at the DOS command line to bypass the minimum requirements, allowing for installation on a CPU as low as the 16 MHz 80486SX. Support lifecycle Compared with other releases of Windows, Windows Me had a short shelf-life of just over a year. Windows 2000 and Windows Me were eventually succeeded by newer Microsoft operating systems: Windows Me by Windows XP Home Edition, and Windows 2000 Professional by Windows XP Professional. Windows XP is noteworthy that the first preview build of Windows XP (then codenamed "Whistler") was released to developers on July 13, 2000, two months before Me's general availability date. Microsoft planned to end support for Windows Me on December 31, 2004. However, in order to give customers more time to migrate to newer Windows versions, particularly in developing or emerging markets, Microsoft decided to extend support until July 11, 2006. Microsoft ended support for Windows Me because the company considered Windows Me to be obsolete and prone to security risks, and recommended customers upgrade to Windows XP for the latest security improvements. Windows Me is no longer available in any form due to the terms of Java-related settlements Microsoft made with Sun Microsystems. The Windows Update website continued to be available after Windows ME's end of support date, however, during 2011, Microsoft retired the Windows Update v4 website and removed the updates for Windows ME from its servers. Microsoft announced in July 2019 that the Microsoft Internet Games services on Windows Me (and XP) would end on July 31, 2019. Reception Windows Me initially received generally positive reviews, with reviewers citing the operating system's integrity protection (branded as "PC Health") and the new System Restore feature as steps forward for home users. However, users' real-world experience did not bear this out, with industry publications receiving myriad reports of issues with the "PC Health" systems, PCs refusing to shut down cleanly, and general stability problems. As time went on, the reception became more negative, to the point where it was heavily panned by users, mainly due to stability issues. Retrospectively, Windows Me is viewed as one of the worst operating systems Microsoft has ever produced, being unfavorably compared to its immediate predecessor and successor. Due to its many bugs and glitches, Windows Me is considered one of the worst operating systems of all time. A PC World article dubbed Windows Me the "Mistake Edition" and placed it 4th in their "Worst Tech Products of All Time" feature in 2006. The article states: "Shortly after Me appeared in late 2000, users reported problems installing it, getting it to run, getting it to work with other hardware or software, and getting it to stop running." Consequently, most home users remained with Windows 98, while some moved to Windows 2000 despite the latter being enterprise-orientated. System Restore suffered from a bug in the date-stamping functionality that could cause System Restore to date-stamp snapshots that were taken after September 8, 2001, incorrectly. This could prevent System Restore from locating these snapshots and cause the system restore process to fail. Microsoft released an update to fix this problem. Byron Hinson and Julien Jay, writing for ActiveWin, took an appreciative look on the operating system. On the removal of real mode DOS, they had noted "The removal of DOS has clearly made a difference in Windows Me in terms of stability (far less Blue screen of death are seen now) and booting speed has greatly increased." In a recommendation of the operating system upgrade for users of Windows 95 and 98, they had stated "If Windows Me isn't a revolutionary OS it's clear that Microsoft has focused its efforts to make it more user-friendly, stable and packed full of multimedia options. The result is great and the enhancements added are really worth the wait." The new features that Windows Me introduced were also praised and have since remained part of subsequent Windows generations. Along with Windows 2000 from the NT family, Windows Me was the last version of Windows that lacked product activation. References External links GUIdebook – Graphical User Interface gallery Interview with Nicolas Coudière, Chief Product Manager: Microsoft Windows Millennium Edition Windows Me home page: The official Windows Me home page from Wayback Machine Windows 9x Member Projects ME DOS variants 2000 software Products and services discontinued in 2006 Turn of the third millennium IA-32 operating systems

Operating System (OS)

Comparison of Microsoft Windows versions Microsoft Windows is the name of several families of computer software operating systems created by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). All versions of Microsoft Windows are commercial proprietary software. General information Basic general information about Windows. DOS shells Has partial 32-bit compatibility with Win32s Windows 9x Windows NT has also an N-edition has also an N-edition has also an N-edition has a separate x64-edition has also a Core-edition has also an edition without HyperV has also a Core-edition without HyperV Windows Embedded Compact Windows Embedded Compact (Windows CE) is a variation of Microsoft's Windows operating system for minimalistic computers and embedded systems. Windows CE is a distinctly different kernel, rather than a trimmed-down version of desktop Windows. It is supported on Intel x86 and compatibles, MIPS, ARM, and Hitachi SuperH processors. Windows Mobile Windows Mobile is Microsoft's discontinued line of operating systems for smartphones. Windows Phone Windows Phone is Microsoft's discontinued line of operating systems for smartphones. Technical information DOS shells Windows 9x It is possible to install the MS-DOS variants 7.0 and 7.1 without the graphics user interface of Windows. If an independent installation of both, DOS and Windows is desired, DOS ought to be installed prior to Windows, at the start of a small partition. The system must be transferred by the (dangerous) "SYSTEM" DOS-command, while the other files constituting DOS can simply be copied (the files located in the DOS-root and the entire COMMAND directory). Such a stand-alone installation of MS-DOS 8 is not possible, as it's designed to work as real mode for Windows Me and nothing else. Windows NT The Windows NT kernel powers all recent Windows operating systems. It runs on IA-32, x64, DEC Alpha, MIPS architecture, PowerPC, Itanium, ARMv7, and ARM64 processors. Windows Phone Supported file systems Various versions of Windows support various file systems, including: FAT12, FAT16, FAT32, HPFS, or NTFS, along with network file systems shared from other computers, and the ISO 9660 and UDF file systems used for CDs, DVDs, and other optical discs such as Blu-ray. Each file system is usually limited in application to certain media, for example CDs must use ISO 9660 or UDF, and as of Windows Vista, NTFS is the only file system which the operating system can be installed on. Windows Embedded CE 6.0, Windows Vista Service Pack 1, and Windows Server 2008 onwards support exFAT, a file system more suitable for USB flash drives. Windows 9x Windows NT Windows Phone Hardware requirements Installing Windows requires an internal or external optical drive, or a USB flash drive. A keyboard and mouse are the recommended input devices, though some versions support a touchscreen. For operating systems prior to Vista, an optical drive must be capable of reading CD media, while in Windows Vista onwards, such a drive must be DVD-compatible. The drive may be detached after installing Windows. Windows 9x Windows NT Windows Phone Physical memory limits Maximum limits on physical memory (RAM) that Windows can address vary depending on both the Windows version and between IA-32 and x64 versions. Windows 9x Windows 95: 480 MB Windows 98: 1 GB Windows Me: 1.5 GB Windows NT Security features Features Timeline See also Other lists List of Microsoft Windows versions List of operating systems Comparison of operating systems Comparison of kernels Comparison of Windows Vista and Windows XP History of Microsoft Windows Comparison of DOS operating systems Architecture of the Windows NT operating system line Microsoft codenames Windows clones and emulators Freedows OS – Windows clone ReactOS – project to develop an operating system that is binary compatible with application software and device drivers for Microsoft Windows NT version 5.x Wine (software) – compatibility layer which allows to execute programs that were originally written for Microsoft Windows References External links Time line from Microsoft German Site about Microsoft Windows history Microsoft Windows

Operating System (OS)

Online OS The Online Operating System was a fully multi-lingual and free to use web desktop written in JavaScript using Ajax. It was a Windows-based desktop environment with open-source applications and system utilities developed upon the reBOX web application framework by iCUBE Network Solutions, an Austrian company located in Vienna. About the project OOS.cc, which is short for Online Operating System, was a web application platform that mimicked the look and feel of classic desktop operating systems such as Microsoft Windows, Mac OS X or KDE. It consisted of various open source applications built upon the so-called reBOX web application framework. As applications could be executed in an integrated and parallel way, the OOS could have been considered a web desktop or webtop. It provided basic services such as a GUI, a virtual file system, access control management and possibilities to develop and deploy applications online. As the Online Operating System was executed within a web browser, it was no real operating system but rather a portal to various web applications, offering a high usability and flexibility. The project was partly funded by grants from the Internetprivatstiftung Austria (IPA). As at 01.08.2008 almost 20.000 users have joined the oos.cc community, using the offered featured and applications. History The development of the web desktop was started by iCUBE Network Solutions in 2005, followed by the first beta releases in 2006. Hence, together with YouOS and eyeOS, it can be considered to be one of the first publicly available systems of its kind. The first full version including core-level multi-language support, the file system and a basic set of applications was released to the public in March 2007 on the occasion of a national exhibition (ITnT Austria) and has left beta state half a year later in October 2007. The first release considered stable (1.0.0) was published in July 2007. The project itself and the contained applications have received several national innovation awards (see,) and have gained attention mainly due to the comprehensive approach taken (see,). OOS.cc started as a national project. The full platform including all offered applications are currently available in three languages (German, English as well as Spanish) and is receiving increasing coverage around the world (for examples see, or). The current version is 1.3.01 from 01.08.2008. Technical Overview The project is fully written in JavaScript, exclusively using DHTML techniques to run in any web browser without any additional software installation needed. The system implements a modern kind of web application model, excessively using Ajax for communicating between client components and the Java server backend in an exclusively asynchronous manner. Aim is to offer users the unique interaction behavior following the desktop metaphor, which is the main idea of any web desktop. Also typical for this sort of web application is the broadly use of Javascript-on-demand techniques, cutting the complete project source into pieces and loading them instantly when needed. Based on this technical basis, reBOX was the framework library all applications in oos.cc were built of. It is a fully flexible and extensible API, including a GUI widget set, communication mechanisms and server services offering general and framework specific services. The Online Operating System itself consisted of a basic framework, which was able to launch any JavaScript application using the reBOX library. The user interface was based on the behavior of the Windows desktop with a start menu, a task bar and a desktop background. All applications were running in this environment. At server side, there were Java based web services that ran to serve the client processes and to provide data from the relational database in the backend. oos.cc also provided an integrated development environment called Developer Suite, which allowed the community to build own applications for the desktop environment based on reBOX (see development section below). License All applications available in oos.cc were open source under the European Union Public Licence (EUPL). The reBOX development toolkit is free to use developing any applications for the webtop. Features As mentioned above, all applications published on oos.cc are open source based on the EUPL, and can be "installed" or "deinstalled" to what-ever preferences the user has. Besides global services like the multi-language support or the global theme support, as well as some minor tools and games, oos.cc offered four major services that could be used completely free of charge. Integrated and fully flexible file storage (1 GB per user) HTTP as well as FTP file transfer from and to local file system User-based file-shares within the oos-community WebDAV access Document Management (including Version Control and File Locking mechanisms) Image publishing, organization and post-processing A free sub domain (user.oos.cc) for web- or image publishing, directly integrated in the desktop Groupware applications, including free mail, fetchmail and contact management An integrated development environment where oos-applications can be created directly from within the system (see development section below) Next releases were planned to focus on an extensive security and privacy suite, dealing with challenges like anonymous communication (browsing as well as temporary mail-addresses) as well as offering encrypted password and file storage and connectivity services. Since its initial stable release, OOS.cc could have been accessed using https to ensure secure communication. Limitations and drawbacks Limited number of applications: no commercial applications can be hosted. Only reviewed applications are being published No processing of popular office formats (.doc, .odt, etc.) Limited language support: Only English, German and Spanish Dependence on foreign infrastructure: No possibility to extend storage, no additional/guaranteed bandwidth, etc. Development One of the key focuses of the team was right from the beginning to offer a very flexible and comprehensive API, that can be used to develop not only custom applications within oos.cc, but also stand-alone web-applications or to integrate single components in existing web-sites. By decoupling the development from web-related "problems" using the reBOX API web-applications can be development in a similar fashion to any Java program: Elements can be positioned and can interact like in high-level object oriented programming languages, without taking care of divs, browser specific behavior or communication handling. The framework also offers multi-language and theme support for existing as well as newly created applications, allowing changing almost every aspect of the look and feel of the used components according to the preferences of its users. For taking advantage of this approach, one of the applications offered in the OOS was an integrated Development Suite, allowing directly writing and executing code and hence creating new programs within the boundaries of the web computer. All applications on oos.cc were released as open source, thus all existing programs were offered to be imported, reviewed or changed and then locally deployed. Following this idea, every user was free to submit changed or newly created applications to be included in the globally offered application set. The last release offered features like auto-completion and an outline-window. See also Web portal Web desktop Similar applications Jolicloud youOS eyeOS DesktopTwo SilveOS G.ho.st The Sky Pc References External links Official Project Homepage [dead] Project Description Official Company Homepage Web desktops Web 2.0 Cloud computing Software using the European Union Public Licence

Operating System (OS)

Macintosh operating systems The family of Macintosh operating systems developed by Apple Inc. includes the graphical user interface-based operating systems it has designed for use with its Macintosh series of personal computers since 1984, as well as the related system software it once created for compatible third-party systems. In 1984, Apple debuted the operating system that is now known as the "Classic" Mac OS with its release of the original Macintosh System Software. The system, rebranded "Mac OS" in 1996, was preinstalled on every Macintosh until 2002 and offered on Macintosh clones for a short time in the 1990s. Noted for its ease of use, it was also criticized for its lack of modern technologies compared to its competitors. The current Mac operating system is macOS, originally named "Mac OS X" until 2012 and then "OS X" until 2016. Developed between 1997 and 2001 after Apple's purchase of NeXT, Mac OS X brought an entirely new architecture based on NeXTSTEP, a Unix system, that eliminated many of the technical challenges that the classic Mac OS faced. The current macOS is preinstalled with every Mac and is updated annually. It is the basis of Apple's current system software for its other devices – iOS, iPadOS, watchOS, and tvOS. Prior to the introduction of Mac OS X, Apple experimented with several other concepts, releasing different products designed to bring the Macintosh interface or applications to Unix-like systems or vice versa, A/UX, MAE, and MkLinux. Apple's effort to expand upon and develop a replacement for its classic Mac OS in the 1990s led to a few cancelled projects, code named Star Trek, Taligent, and Copland. Although they have different architectures, the Macintosh operating systems share a common set of GUI principles, including a menu bar across the top of the screen; the Finder shell, featuring a desktop metaphor that represents files and applications using icons and relates concepts like directories and file deletion to real-world objects like folders and a trash can; and overlapping windows for multitasking. Classic Mac OS The "classic" Mac OS is the original Macintosh operating system that was introduced in 1984 alongside the first Macintosh and remained in primary use on Macs until the introduction of Mac OS X in 2001. Apple released the original Macintosh on January 24, 1984; its early system software was partially based on the Lisa OS and the Xerox PARC Alto computer, which former Apple CEO Steve Jobs previewed. It was originally named "System Software", or simply "System"; Apple rebranded it as "Mac OS" in 1996 due in part to its Macintosh clone program that ended a year later. Classic Mac OS is characterized by its monolithic design. Initial versions of the System Software run one application at a time. System 5 introduced cooperative multitasking. System 7 supports 32-bit memory addressing and virtual memory, allowing larger programs. Later updates to the System 7 enable the transition to the PowerPC architecture. The system was considered user-friendly, but its architectural limitations were critiqued, such as limited memory management, lack of protected memory and access controls, and susceptibility to conflicts among extensions. Releases Nine major versions of the classic Mac OS were released. The name "Classic" that now signifies the system as a whole is a reference to a compatibility layer that helped ease the transition to Mac OS X. Macintosh System Software – "System 1", released in 1984 System Software 2, 3, and 4 – released between 1985 and 1987 System Software 5 – released in 1987 System Software 6 – released in 1988 System 7 / Mac OS 7.6 – released in 1991 Mac OS 8 – released in 1997 Mac OS 9 – final major version, released in 1999 Mac OS X / OS X / macOS macOS (originally named "Mac OS X" until 2012 and then "OS X" until 2016) is the current Mac operating system that officially succeeded the classic Mac OS in 2001. Although the system was originally marketed as simply "version 10" of Mac OS, it has a history that is largely independent of the classic Mac OS. It is a Unix-based operating system built on NeXTSTEP and other technology developed at NeXT from the late 1980s until early 1997, when Apple purchased the company and its CEO Steve Jobs returned to Apple. Precursors to the original release of Mac OS X include OPENSTEP, Apple's Rhapsody project, and the Mac OS X Public Beta. macOS makes use of the BSD codebase and the XNU kernel, and its core set of components is based upon Apple's open source Darwin operating system. macOS is the basis for some of Apple's other operating systems, including iPhone OS/iOS, iPadOS, watchOS, and tvOS. Releases Desktop The first desktop version of the system was released on March 24, 2001, supporting the Aqua user interface. Since then, several more versions adding newer features and technologies have been released. Since 2011, new releases have been offered on an annual basis. Mac OS X 10.0 – code name "Cheetah", released to end users on Saturday, March 24, 2001 Mac OS X 10.1 – code name "Puma", released to end users on Tuesday, September 25, 2001 Mac OS X 10.2 – also marketed as "Jaguar", released to end users on Friday, August 23, 2002 Mac OS X Panther – version 10.3, released to end users on Friday, October 24, 2003 Mac OS X Tiger – version 10.4, released to end users on Friday, April 29, 2005 Mac OS X Leopard – version 10.5, released to end users on Friday, October 26, 2007 Mac OS X Snow Leopard – version 10.6, publicly unveiled on Monday, June 8, 2009 Mac OS X Lion – version 10.7, released to end users on Wednesday, July 20, 2011 OS X Mountain Lion – version 10.8, released to end users on Wednesday, July 25, 2012 OS X Mavericks – version 10.9, released to end users on Tuesday, October 22, 2013 OS X Yosemite – version 10.10, released to end users on Thursday, October 16, 2014 OS X El Capitan – version 10.11, released to end users on Wednesday, September 30, 2015 macOS Sierra – version 10.12, released to end users on Tuesday, September 20, 2016 macOS High Sierra – version 10.13, released to end users on Monday, September 25, 2017 macOS Mojave – version 10.14, released to end users on Monday, September 24, 2018 macOS Catalina – version 10.15, released to end users on Monday, October 7, 2019 macOS Big Sur – version 11, released to end users on Thursday, November 12, 2020 macOS Monterey – version 12, released to end users on Monday, October 25, 2021 Server An early server computing version of the system was released in 1999 as a technology preview. It was followed by several more official server-based releases. Server functionality has instead been offered as an add-on for the desktop system since 2011. Mac OS X Server 1.0 – code name "Hera", released in 1999 macOS Server – several releases since 2001 Other projects Shipped A/ROSE The Apple Real-time Operating System Environment (A/ROSE) was a small embedded operating system which ran on the Macintosh Coprocessor Platform, an expansion card for the Macintosh. The idea was to offer a single "overdesigned" hardware platform on which third-party vendors could build practically any product, reducing the otherwise heavy workload of developing a NuBus-based expansion card. The first version of the system was ready for use in February 1988. A/UX In 1988, Apple released its first UNIX-based OS, A/UX, which was a UNIX operating system with the Mac OS look and feel. It was not very competitive for its time, due in part to the crowded UNIX market and Macintosh hardware lacking high-end design features present on workstation-class computers. A/UX had most of its success in sales to the U.S. government, where POSIX compliance was a requirement that Mac OS could not meet. MAE The Macintosh Application Environment (MAE) was a software package introduced by Apple in 1994 that allowed users of certain Unix-based computer workstations to run Apple Macintosh application software. MAE used the X Window System to emulate a Macintosh Finder-style graphical user interface. The last version, MAE 3.0, was compatible with System 7.5.3. MAE was available for Sun Microsystems SPARCstation and Hewlett-Packard systems. It was discontinued on May 14, 1998. MkLinux Announced at the 1996 Worldwide Developers Conference (WWDC), MkLinux is an open source operating system that was started by the OSF Research Institute and Apple in February 1996 to port Linux to the PowerPC platform, and thus Macintosh computers. In mid 1998, the community-led MkLinux Developers Association took over development of the operating system. MkLinux is short for "Microkernel Linux," which refers to the project's adaptation of the Linux kernel to run as a server hosted atop the Mach microkernel. MkLinux is based on version 3.0 of Mach. Cancelled Star Trek Star Trek (as in "to boldly go where no Mac has gone before") was a relatively unknown secret prototype beginning in 1992, whose goal was to create a version of the classic Mac OS that would run on Intel-compatible x86 personal computers. In partnership with Apple and with support from Intel, the project was instigated by Novell, which was looking to integrate its DR-DOS with the Mac OS GUI as a mutual response to the monopoly of Microsoft's Windows 3.0 and MS-DOS. A team consisting of four from Apple and four from Novell was able to get the Macintosh Finder and some basic applications such as QuickTime, running smoothly on the x86 architecture. The project was canceled a year later in early 1993, but some of the code was later reused when porting the Mac OS to PowerPC. Taligent Taligent (a portmanteau of "talent" and "intelligent") was the name of an object-oriented operating system and the company dedicated to producing it. Started as a project within Apple to provide a replacement for the classic Mac OS, it was later spun off into a joint venture with IBM as part of the AIM alliance, with the purpose of building a competing platform to Microsoft Cairo and NeXTSTEP. The development process never worked, and Taligent is often cited as an example of a project death march. Apple pulled out of the project in 1995 before the code had been delivered. Copland Copland was a project at Apple to create an updated version of the classic Mac OS. It was to have introduced protected memory, preemptive multitasking and a number of new underlying operating system features, yet still be compatible with existing Mac software. As originally planned, a follow-up release known as "Gershwin" would add multithreading and other advanced features. New features were added more rapidly than they could be completed, and the completion date slipped into the future with no sign of a release. In 1996, Apple decided to cancel the project outright and find a suitable third-party system to replace it. Copland development ended in August 1996, and in December 1996, Apple announced that it was buying NeXT for its NeXTSTEP operating system. Timeline Related systems Before the arrival of the Macintosh in 1984, Apple's history of operating systems began with its Apple II series computers in 1977, which ran Apple DOS, ProDOS, and later GS/OS; the Apple III in 1980, which ran Apple SOS; and the Apple Lisa in 1983, which ran Lisa OS and later MacWorks XL, a Macintosh emulator. Apple also developed the Newton OS for its Newton personal digital assistant from 1993 to 1997. In recent years, Apple has also launched several new operating systems based on the core of macOS, including iOS in 2007 for its iPhone, iPad, and iPod Touch mobile devices and in 2017 for its HomePod smart speakers; watchOS in 2015 for the Apple Watch; tvOS in 2015 for the Apple TV set-top box. See also Comparison of operating systems History of the graphical user interface Macintosh List of Macintosh software References External links Apple Inc. software History of software Lists of operating systems Macintosh operating systems development Operating system families Software version histories

Operating System (OS)

V (operating system) The V operating system (sometimes written V-System) is a discontinued microkernel distributed operating system that was developed by faculty and students in the Distributed Systems Group at Stanford University from 1981 to 1988, led by Professors David Cheriton and Keith A. Lantz. V was the successor to the Thoth operating system and Verex kernel that Cheriton had developed in the 1970s. Despite similar names and close development dates, it is unrelated to UNIX System V. Features The key concepts in V are multithreading and synchronous message passing. The original V terminology uses process for what is now commonly called a thread, and team for what is now commonly called a process consisting of multiple threads sharing an address space. Communication between threads in V uses synchronous message passing, with short, fixed-length messages that can include access rights for the receiver to read or write part of the sender's address space before replying. The same message-passing interface is used both between threads within one process, between threads of different processes within one machine, and between threads on different machines connected by a local Ethernet. A thread receiving a message is not required to reply to it before receiving other messages; this distinguished the model from Ada rendezvous. One common pattern for using the messaging facility is for clients to send messages to a server requesting some form of service. From the client side, this looks much like a remote procedure call (RPC). The convenience of an automatic stub generator was lacking, but in contrast, the client can pass one parameter by reference, which is not possible with other RPC implementations. From the server side the model differs more from RPC, since by default all client requests are multiplexed onto one server thread. The server is free to explicitly fork threads to handle client requests in parallel, however; if this is done, the server-side model is much like RPC too. V was never an end in itself for the Stanford group; rather, it was used as a vehicle for many different research projects in distributed operating systems and networking. Much like other operating system efforts of its day (such as Sprite), V was a complete system that was mostly self hosting. Many students ran V as the only operating system on their diskless SUN workstations or MicroVAX workstations. Compiles could be done either on V, or on VAX Unix machines that provided file service in a more stable environment than the ever-changing research system. V did have some notable impacts. After the initial implementation on one computer, the Versatile Message Transaction Protocol (VMTP) was developed to extend the send-receive-reply system call semantics over a local area network. The protocol included multicast support developed by Steve Deering as a graduate student in the group. The Internet Protocol layer to support this evolved into the IP multicast standard. The V system was used for graphical user interface (GUI) research. The Virtual Graphics Terminal Service (VGTS) provided a modular windowing system for both local and remote applications. The little-known W Window System got its name because it was first hosted on the V operating system, and the better-known X Window System in turn got its name because its first version was based partly on W. V also spawned another pure microkernel effort at Apple Computer known as Vanguard, which added a number of improvements to the basic system. Vanguard later disappeared in a reorganization. The Tektronix VM700 television measurement instrument was developed in a networked V environment in the late 1980s and ran a lightly modified version of the V operating system; this device was manufactured and sold for many years. Commands The following is a list of workstation commands that are supported by the V operating system version 6.0 command-line interface. addcorr amaze ar biopsy bitcompile bits boise build cat cc68 cd checkers checkexecs ci clear clock co cp cpdir cx dale date debug debugvgts define delcorr delexec destroy diff do domake dopar doseq draw echo fexecute freemem gftodvi gftyoe grep hack ident instances internetserver iphost killprog listdir listdesc login logout mail memserver mf migrateprog mon name newterm pagemode password pc68 pwd pwx Q query queryexec ranlib68 rcs rcsdiff rcsmerge rename rlog rm sed serial show sleep sort startexec storagestats stuffboot tail talk telnet telnetserver testexcept timeipc timekernel tsort type undefine ved vemacs w wc wh whi References External links V system documentation at Bitsavers.org Microkernels Stanford University Discontinued operating systems Distributed operating systems Microkernel-based operating systems

Operating System (OS)

SunOS SunOS is a Unix-branded operating system developed by Sun Microsystems for their workstation and server computer systems. The SunOS name is usually only used to refer to versions 1.0 to 4.1.4, which were based on BSD, while versions 5.0 and later are based on UNIX System V Release 4, and are marketed under the brand name Solaris. History SunOS 1 only supported the Sun-2 series systems, including Sun-1 systems upgraded with Sun-2 (68010) CPU boards. SunOS 2 supported Sun-2 and Sun-3 (68020) series systems. SunOS 4 supported Sun-2 (until release 4.0.3), Sun-3 (until 4.1.1), Sun386i (4.0, 4.0.1 and 4.0.2 only) and Sun-4 (SPARC) architectures. Although SunOS 4 was intended to be the first release to fully support Sun's new SPARC processor, there was also a SunOS 3.2 release with preliminary support for Sun-4 systems. SunOS 4.1.2 introduced support for Sun's first sun4m-architecture multiprocessor machines (the SPARCserver 600MP series); since it had only a single lock for the kernel, only one CPU at a time could execute in the kernel. The last release of SunOS 4 was 4.1.4 (Solaris 1.1.2) in 1994. The sun4, sun4c and sun4m architectures were supported in 4.1.4; sun4d was not supported. Sun continued to ship SunOS 4.1.3 and 4.1.4 until December 27, 1998; they were supported until September 30, 2003. "SunOS" and "Solaris" In 1987, AT&T Corporation and Sun announced that they were collaborating on a project to merge the most popular Unix flavors on the market at that time: BSD (including many of the features then unique to SunOS), System V, and Xenix. This would become System V Release 4 (SVR4). On September 4, 1991, Sun announced that its next major OS release would switch from its BSD-derived source base to one based on SVR4. Although the internal designation of this release would be SunOS 5, from this point Sun began using the marketing name Solaris. The justification for this new "overbrand" was that it encompassed not only SunOS, but also the OpenWindows desktop environment and Open Network Computing (ONC) functionality. Even though the new SVR4-based OS was not expected to ship in volume until the following year, Sun immediately began using the new Solaris name to refer to the currently shipping SunOS 4 release (also including OpenWindows). Thus SunOS 4.1.1 was rebranded Solaris 1.0; SunOS 5.0 would be considered a part of Solaris 2.0. SunOS 4.1.x micro versions continued to be released through 1994, and each of these was also given a Solaris 1.x equivalent name. In practice, these were often still referred to by customers and even Sun personnel by their SunOS release names. Matching the version numbers was not straightforward: Today, SunOS 5 is universally known as Solaris, although the SunOS name is still visible within the OS itself in the startup banner, the output of the uname command, and man page footers, among other places. Matching a SunOS 5.x release to its corresponding Solaris marketing name is simple: each Solaris release name includes its corresponding SunOS 5 minor version number. For example, Solaris 2.4 incorporated SunOS 5.4. There is one small twist: after Solaris 2.6, the "2." was dropped from the Solaris name and the SunOS minor number appears by itself. The latest Solaris release is named Solaris 11 and incorporates SunOS 5.11. User interface GUI environments bundled with earlier versions of SunOS included SunTools (later SunView) and NeWS. In 1989, Sun released OpenWindows, an OPEN LOOK-compliant X11-based environment which also supported SunView and NeWS applications. This became the default SunOS GUI in SunOS 4.1.1. See also Comparison of BSD operating systems Comparison of operating systems Illumos OpenSolaris OpenIndiana Solaris (operating system) Unix wars References External links The Sun Hardware Reference (Overview) An Introduction to Solaris – a sample chapter from Solaris Internals: Core Kernel Architecture by Jim Mauro & Richard McDougall, Prentice-Hall, 2000. (PDF) Info on SunOS from OSdata (last updated February 17, 2002) Initial Solaris announcement Berkeley Software Distribution Discontinued operating systems Sun Microsystems software UNIX System V

Operating System (OS)

System 6 System 6 (or System Software 6) is a graphical user interface-based operating system for Macintosh computers, made by Apple Computer, Inc. It was released in 1988, and is part of the classic Mac OS series. It is a monolithic operating system, with cooperative multitasking based on an improved MultiFinder. The boxed version cost , and it was included with all new Macintosh computers until 1991, when it was succeeded by System 7. Features MacroMaker The MacroMaker utility was introduced in System 6. It records mouse and keyboard input as macros, and has a unique user interface intended to look and act like a tape recorder. MacroMaker was criticized for its lack of features when compared to Microsoft's AutoMac III, which was already available commercially. As MacroMaker records only the locations of mouse-clicks inside windows and not what is being clicked on or exactly when, it can not be used to automate actions in more sophisticated programs. The pre-recorded clicks miss buttons if the buttons had moved since the recording, or if they failed to appear upon playback. It records the start and end locations of mouse movements, but does not track the precise path of a movement or support pauses. MacroMaker is not compatible with System 7, in which it is succeeded by AppleScript. Multitasking Macintosh gained cooperative multitasking in March 1985 with Andy Hertzfeld's Switcher, which can switch between multiple full-screen applications. It was not integrated, and was only sold separately by Apple. Not many programs and features function correctly with Switcher, and it does not share the screen between applications simultaneously. Systems 5 and 6 have MultiFinder instead, which is much more mature and widely used in System 6. With MultiFinder, the Finder does not quit to free resources, and the system behaves as in the still-familiar multitasking fashion, with the desktop and other applications' windows in the background. Hardware support System 6 includes support for the Apple ImageWriter LQ and PostScript laser printers. New software drivers allow the ImageWriter LQ to be used on AppleTalk local area networks and supports the use of tabloid or B-size paper (). System 6 includes QuickerGraf (originally QuickerDraw), system software used to accelerate the drawing of color images on the Macintosh II. It was licensed to Apple and Radius Inc by its programmer, Andy Hertzfeld. Limitations In comparison to the NeXTSTEP operating system of the time, System 6 does not make much use of sound, and its user interface is limited in file management and window displays. System 6's Apple menu cannot be used to launch applications. The icon in the upper right-hand corner of the menu bar simply shows the open application and is not a menu. System 6 supports 24 bits of addressable RAM (random access memory), which allows for a maximum of 8 megabytes of RAM, with no provision for virtual memory. These limitations were removed in System 7. System 6's version of the HFS file system also has a volume size limit; it supports up to 2 gigabytes (GB) and 65,536 files on any one volume. System 7.5 increased this limit to 4 GB. The Trash (known as the "Wastebasket" in the British-English version) empties when the Finder terminates. If MultiFinder is not running, this occurs as soon as an application launches. Icons on the Desktop in System 6 are not organized into a single folder, as in later operating systems. Instead, the system records if a file is on the Desktop. This is inefficient and confusing, as the user cannot browse to the Desktop in applications besides the Finder, even within the standard Open and Save As dialog boxes. Furthermore, these dialogs are primitive, and were mostly unchanged since 1984. The lack of aliases, shortcuts to files, is another limitation of file management on System 6, and custom file and folder icons are not supported. These issues were all remedied in System 7. A maximum of 15 desk accessories may be installed at one time, including the Chooser, Scrapbook, and Control Panel. System 6 uses the Control Panel desk accessory to access all the installed control panels, which imposes severe user-interface limitations. Desk Accessories cannot be installed or removed within the Finder; this requires the Font/DA Mover utility. System 7 also fixed this. Control Panels, however, are contained in separate files. The interface is not very customizable. The Finder allows each icon to be assigned a color, but the desktop background is limited to an 8x8-pixel color tiled pattern (color patterns were introduced in System 5), and standard window frames are black-and-white. However, many "INIT" extension files exist to add color and customization. System 7 allows the user to change the color of window frames and various other aspects of the user interface. By 1989, the System 6 user interface was in need of a change. Reception Initial releases of System 6 are unstable; many third-party developers did not receive advance copies, resulting in widespread compatibility issues. The contemporary versions of many common programs such as Microsoft Excel, Microsoft Works and 4th Dimension were not fully compatible with System 6. There were also software bugs in the Color Manager, Script Manager, and Sound Manager extension files. Apple announced that 66 bugs were fixed with version 6.0.1 update, in September 1988. However, a major bug involving the text-spacing of screen fonts was found, and was fixed in version 6.0.2. Some customers waited longer until moving to System 6 because of its poor reputation. Compatibility System 6 was officially supported by Apple for many different machines, some of which shipped with it. Some unsupported Macintosh computers can run it with limitations. Version history References External links Macintosh: System Software Version History at apple.com 1988 software Classic Mac OS Proprietary operating systems Pascal (programming language) software

Operating System (OS)

Embedded operating system An embedded operating system is an operating system for embedded computer systems. Embedded operating systems are computer systems designed for a specific purpose, to increase functionality and reliability for achieving a specific task. Resource efficiency comes at the cost of losing some functionality or granularity that larger computer operating systems provide, including functions which may not be used by the specialized applications they run. Depending on the method used for multitasking, this type of OS is frequently considered to be a real-time operating system, or RTOS. Embedded systems are mostly used as Real-time operating systems. All embedded systems contain a processor and software. There must be a place for embedded software to store the executable code and temporary storage for run-time data manipulations. These take the form of ROM and RAM respectively. All embedded systems must also contain some form of inputs and outputs to function. Within the exception of these few common features, the rest of the embedded hardware is usually unique and varies from application to application. The hardware running an embedded operating system can be very limited in resources, therefore embedded design of these operating systems may have a narrow scope tailored to a specific application to achieve desired operation under these constraints. The embedded operating system that organizes and controls the hardware usually determines the rest of the embedded hardware needed. In order to take better advantage of the processing power of the CPU, software developers may write critical code directly in assembly. This machine efficient language can potentially result in gains in speed and determinism at the cost of portability and maintainability. Often, embedded operating systems are written entirely in more portable languages, like C, however. An important difference between most embedded operating systems and desktop operating systems is that the application, including the operating system, is usually statically linked together into a single executable image. Unlike a desktop operating system, the embedded operating system does not load and execute a lot of applications. This means that the system is only able to run a few application(s). History The Development of Embedded Operating Systems In the late 1970s, the concept of real-time multitasking kernel was proposed. In 1980s, while the applications of embedded system became more and more complex, the embedded operating system with real-time multitasking kernel could not meet the requirement of embedded development. It began to develop into a complete Real-Time multitasking Operating System (RTOS) that included a network, file, development and debugging environment. Nowadays, RTOS has formed an industry in the world. The world's first commercial embedded real-time kernel (VRTX32) was developed by Ready System in 1981. Then in 1993, Ready System and the famous Silicon Valley embedded software company Microtec Research Merger developed two new RTOS kernel VRTX32 and VRTXsa on the basis of VRTXmc. At the same time, VRTX integrated development environment (Spectra) appeared. Microsoft, also released its own embedded 460 operating system in 1996. The embedded operating system is WinCE, which was originally based on Windows 95 in the 1.0 version, they subsequently released other versions, supporting x86, ARM, SH4, MIPS and other processor architectures. WinCE is now defunct, with mainstream support ended in 2018. Modern embedded systems - Smartphones and Internet of Things Nowadays, many embedded devices are used in the system of Internet of Things and hundreds of sensors are used in a car. Compared with the traditional embedded system, the Internet of Things system requires lower power consumption, more safety and reliability, and has the ability of ad hoc network. The communication section needs to meet the conversion between various communication protocols and the application layer must have the ability of cloud computing. The emergence of Smartphones have also resulted Due to this, new embedded operating systems have emerged and become popular, like Embedded Linux (including OpenWrt, Zeroshell, Android, LineageOS, LEDE, LibreCMC etc.,), NetBSD, ThreadX, FreeRTOS etc., Many Linux-based projects, toolkits, frameworks etc., have also emerged for embedded systems. Some notable examples include OpenEmbedded, BusyBox, uClibc, musl libc, buildroot etc., See also Embedded Linux Embeddable Linux Kernel Subset, a Linux operating system that fits on a floppy disk List of embedded operating systems OpenWrt Principle of least privilege (computer security) References Embedded operating system

Operating System (OS)

Operating environment In computer software, an operating environment or integrated applications environment is the environment in which users run application software. The environment consists of a user interface provided by an applications manager and usually an application programming interface (API) to the applications manager. An operating environment is not a full operating system, but is a form of middleware that rests between the OS and the application. For example, the first version of Microsoft Windows, Windows 1.0, was not a full operating system, but a GUI laid over DOS albeit with an API of its own. Similarly, the IBM U2 system operates on both Unix/Linux and Windows NT. Usually the user interface is text-based or graphical, rather than a command-line interface (e.g., DOS or the Unix shell), which is often the interface of the underlying operating system. In the mid 1980s, text-based and graphical user interface operating environments surrounded DOS operating systems with a shell that turned the user's display into a menu-oriented "desktop" for selecting and running PC applications. These operating environment systems allow users much of the convenience of integrated software without locking them into a single package. History DOS operating environments In the mid 1980s, text-based and graphical user interface operating environments such as IBM TopView, Microsoft Windows, Digital Research's GEM Desktop, GEOS and Quarterdeck Office Systems's DESQview surrounded DOS operating systems with a shell that turned the user's display into a menu-oriented "desktop" for selecting and running PC applications. These programs were more than simple menu systems—as alternate operating environments they were substitutes for integrated programs such as Framework and Symphony, that allowed switching, windowing, and cut-and-paste operations among dedicated applications. These operating environment systems gave users much of the convenience of integrated software without locking them into a single package. Alternative operating environments made TSR pop-up utilities such as Borland Sidekick redundant. Windows provided its own version of these utilities, and placing them under central control could eliminate memory conflicts that RAM-resident utilities create. In later versions, Windows evolved from an operating environment into a complete operating system with DOS as a bootloader (Windows 9x) and a complete operating system, Windows NT, was developed at the same time. All versions after Windows ME have been based on the Windows NT kernel. See also Desktop environment, the graphical user interface to the computer File manager Integrated environment Integrated development environment, a type of computer software that assists computer programmers in developing software Runtime environment, a virtual machine state which provides software services for processes or programs while a computer is running X Window System References Computing terminology Middleware Operating system APIs User interfaces

Operating System (OS)

Security-evaluated operating system In computing, security-evaluated operating systems have achieved certification from an external security-auditing organization, the most popular evaluations are Common Criteria (CC) and FIPS 140-2. Oracle Solaris Trusted Solaris 8 was a security-focused version of the Solaris Unix operating system. Aimed primarily at the government computing sector, Trusted Solaris adds detailed auditing of all tasks, pluggable authentication, mandatory access control, additional physical authentication devices, and fine-grained access control(FGAC). Versions of Trusted Solaris through version 8 are Common Criteria certified. See and Trusted Solaris Version 8 received the EAL4 certification level augmented by a number of protection profiles. See for explanation of The Evaluation Assurance Levels. BAE Systems' STOP BAE Systems' STOP version 6.0.E received an EAL4+ in April 2004 and the 6.1.E version received an EAL5+ certification in March 2005. STOP version 6.4 U4 received an EAL5+ certification in July 2008. Versions of STOP prior to STOP 6 have held B3 certifications under TCSEC. While STOP 6 is binary compatible with Linux, it does not derive from the Linux kernel. See for an overview of the system. Red Hat Enterprise Linux 5 Red Hat Enterprise Linux 5 achieved EAL4+ in June 2007. Red Hat Enterprise Linux 6 Red Hat Enterprise Linux Version 6.2 on 32 bit x86 Architecture achieved EAL4+ in December 2014. Red Hat Enterprise Linux Version 6.2 with KVM Virtualization for x86 Architectures achieved EAL4+ in October 2012. Novell SUSE Linux Enterprise Server Novell's SUSE Linux Enterprise Server 9 running on an IBM eServer was certified at CAPP/EAL4+ in February 2005. See News release at heise.de Microsoft Windows The following versions of Microsoft Windows have received EAL 4 Augmented ALC_FLR.3 certification: Windows 2008 Server (64-bit), Enterprise (64-bit) and Datacenter, as well as Windows Vista Enterprise (both 32-bit and 64-bit) attained EAL 4 Augmented (colloquially referred to as EAL 4+) ALC_FLR.3 status in 2009. Windows 2000 Server, Advanced Server, and Professional, each with Service Pack 3 and Q326886 Hotfix operating on the x86 platform were certified as CAPP/EAL 4 Augmented ALC_FLR.3 in October 2002. (This includes standard configurations as Domain Controller, Server in a Domain, Stand-alone Server, Workstation in a Domain, Stand-alone Workstation) Windows XP Professional and Embedded editions, with Service Pack 2, and Windows Server 2003 Standard and Enterprise editions (32-bit and 64-bit), with Service Pack 1, were all certified in December 2005. Mac OS X Apple's Mac OS X and Mac OS X Server running 10.3.6 both with the Common Criteria Tools Package installed were certified at CAPP/EAL3 in January 2005. Apple's Mac OS X & Mac OS X Server running the latest version 10.4.6 have not yet been fully evaluated however the Common Criteria Tools package is available. GEMSOS Gemini Multiprocessing Secure Operating System is a TCSEC A1 system that runs on x86 processor type COTS hardware. OpenVMS and SEVMS The SEVMS enhancement to VMS was a CC B1/B3 system formerly of Digital Equipment Corporation (DEC). A standard OpenVMS installation is rated as CC C2. Green Hills INTEGRITY-178B Green Hills Software's INTEGRITY-178B real-time operating system was certified at Common Criteria EAL6+ in September 2008. running on an embedded PowerPC processor on a Compact PCI card. Unisys MCP The Unisys MCP operating system includes an implementation of the DoD Orange Book C2 specification, the controlled access protection sub-level of discretionary protection. MCP/AS obtained the C2 rating in August, 1987. Unisys OS 2200 The Unisys OS 2200 operating system includes an implementation of the DoD Orange Book B1, Labeled security protection level specification. OS 2200 first obtained a successful B1 evaluation in September, 1989. Unisys maintained that evaluation until 1994 through the National Computer Security Center Rating Maintenance Phase (RAMP) of the Trusted Product Evaluation Program. See also Comparison of operating systems Security-focused operating system Trusted operating system External links The common criteria portal's products list has an "Operating Systems" category containing CC certification results References Operating system security Computer security procedures

Operating System (OS)

Security-focused operating system This is a list of operating systems specifically focused on security. Operating systems for general-purpose usage may be secure without having a specific focus on security. Similar concepts include security-evaluated operating systems that have achieved certification from an auditing organization, and trusted operating systems that provide sufficient support for multilevel security and evidence of correctness to meet a particular set of requirements. Linux Android-based GrapheneOS is a free and open source privacy and security focused Android Custom ROM Kali NetHunter is a free and open source Kali Linux based mobile operating system usually for Android devices Debian-based Subgraph is a Linux-based operating system designed to be resistant to surveillance and interference by sophisticated adversaries over the Internet. Subgraph OS is designed with features that aim to reduce the attack surface of the operating system, and increase the difficulty required to carry out certain classes of attack. This is accomplished through system hardening and a proactive, ongoing focus on security and attack resistance. Subgraph OS also places emphasis on ensuring the integrity of installed software packages through deterministic compilation. Subgraph OS features a kernel hardened with the Grsecurity and PaX patchset, Linux namespaces, and Xpra for application containment, mandatory file system encryption using LUKS, resistance to cold boot attacks, and is configured by default to isolate network communications for installed applications to independent circuits on the Tor anonymity network. Tails is a security-focused Linux distribution aimed at preserving privacy and anonymity. It is meant to be run as Live-CD or from a USB Drive and to not write any kind of data to a drive, unless specified or persistence is set. That way, it lives in RAM and everything is purged from the system whenever it is powered off. Tails is designed to do an emergency shutdown and erase its data from RAM if the medium where it resides is expelled. Whonix is an anonymous general purpose operating system based on VirtualBox, Debian Linux and Tor. By Whonix design, IP and DNS leaks are impossible. Not even Malware as Superuser can find out the user's real IP address/location. This is because Whonix consists of two (virtual) machines. One machine solely runs Tor and acts as a gateway, called Whonix-Gateway. The other machine, called Whonix-Workstation, is on a completely isolated network. It is also possible to use multiple Whonix Workstations simultaneously through one Gateway, that will provide stream isolation (though is not necessarily endorsed). All the connections are forced through Tor with the Whonix Gateway Virtual Machine, therefore IP and DNS leaks are impossible. Fedora-based Qubes OS is a desktop operating system based around the Xen hypervisor that allows grouping programs into a number of isolated sandboxes (virtual machines) to provide security. Windows for programs running within these sandboxes ("security domains") can be color coded for easy recognition. The security domains are configurable, they can be transient (changes to the file system will not be preserved), and their network connection can be routed through special virtual machines (for example one that only provides Tor networking). The operating system provides secure mechanisms for copy and paste and for copying files between the security domains Gentoo-based Pentoo is a Live CD and Live USB designed for penetration testing and security assessment. Based on Gentoo Linux, Pentoo is provided both as 32 and 64-bit installable live CD. It is built on Hardened Gentoo linux including a hardened kernel and a toolchain. Tin Hat Linux is derived from Hardened Gentoo Linux. It aims to provide a very secure, stable, and fast desktop environment that lives purely in RAM. Other Linux distributions Alpine Linux is an actively maintained lightweight musl and BusyBox-based distribution. It uses PaX and grsecurity patches in the default kernel and compiles all packages with stack-smashing protection. Annvix was originally forked from Mandriva to provide a security-focused server distribution that employs ProPolice protection, hardened configuration, and a small footprint. There were plans to include full support for the RSBAC mandatory access control system. Annvix is dormant, however, with the last version being released on 30 December 2007. EnGarde Secure Linux is a secure platform designed for servers. It has had a browser-based tool for MAC using SELinux since 2003. Additionally, it can be accompanied with Web, DNS, and email enterprise applications, specifically focusing on security without any unnecessary software. The community platform of EnGarde Secure Linux is the bleeding-edge version freely available for download. Immunix was a commercial distribution of Linux focused heavily on security. They supplied many systems of their own making, including StackGuard; cryptographic signing of executables; race condition patches; and format string exploit guarding code. Immunix traditionally releases older versions of their distribution free for non-commercial use. The Immunix distribution itself is licensed under two licenses: The Immunix commercial and non-commercial licenses. Many tools within are GPL, however, as is the kernel. Solar Designer's Openwall Project (Owl) was the first distribution to have a non-executable userspace stack, /tmp race condition protection, and access control restrictions to /proc data, by way of a kernel patch. It also features a per-user tmp directory via the pam_mktemp PAM module, and supports Blowfish password encryption. BSD-based TrustedBSD is a sub-project of FreeBSD designed to add trusted operating system extensions, targeting the Common Criteria for Information Technology Security Evaluation (see also Orange Book). Its main focuses are working on access control lists, event auditing, extended attributes, mandatory access controls, and fine-grained capabilities. Since access control lists are known to be confronted with the confused deputy problem, capabilities are a different way to avoid this issue. As part of the TrustedBSD project, there is also a port of NSA's FLASK/TE implementation to run on FreeBSD. Many of these trusted extensions have been integrated into the main FreeBSD branch starting at 5.x. OpenBSD is a research operating system for developing security mitigations. Object-capability systems These operating systems are all engineered around the object-capabilities security paradigm, where instead of having the system deciding if an access request should be granted the bundling of authority and designation makes it impossible to request anything not legitimate. CapROS EROS Genode Fiasco.OC KeyKOS seL4 Solaris-based Trusted Solaris was a security-focused version of the Solaris Unix operating system. Aimed primarily at the government computing sector, Trusted Solaris adds detailed auditing of all tasks, pluggable authentication, mandatory access control, additional physical authentication devices, and fine-grained access control. Trusted Solaris is Common Criteria certified. The most recent version, Trusted Solaris 8 (released 2000), received the EAL4 certification level augmented by a number of protection profiles. Telnet was vulnerable to buffer overflow exploits until patched in April 2001. See also References Operating system security Operating system technology Security

Operating System (OS)

POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interfaces (API), along with command line shells and utility interfaces, for software compatibility (portability) with variants of Unix and other operating systems. POSIX is also a trademark of the IEEE. POSIX is intended to be used by both application and system developers. Name Originally, the name "POSIX" referred to IEEE Std 1003.1-1988, released in 1988. The family of POSIX standards is formally designated as IEEE 1003 and the ISO/IEC standard number is ISO/IEC 9945. The standards emerged from a project that began around 1985. Richard Stallman suggested the name POSIX (pronounced as pahz-icks, as in positive, not as poh-six) to the IEEE instead of former IEEE-IX. The committee found it more easily pronounceable and memorable, and thus adopted it. Overview Unix was selected as the basis for a standard system interface partly because it was "manufacturer-neutral". However, several major versions of Unix existed—so there was a need to develop a common-denominator system. The POSIX specifications for Unix-like operating systems originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents (POSIX.1, POSIX.2, etc.). The standardized user command line and scripting interface were based on the UNIX System V shell. Many user-level programs, services, and utilities (including awk, echo, ed) were also standardized, along with required program-level services (including basic I/O: file, terminal, and network). POSIX also defines a standard threading library API which is supported by most modern operating systems. In 2008, most parts of POSIX were combined into a single standard (IEEE Std 1003.1-2008, also known as POSIX.1-2008). , POSIX documentation is divided into two parts: POSIX.1, 2013 Edition: POSIX Base Definitions, System Interfaces, and Commands and Utilities (which include POSIX.1, extensions for POSIX.1, Real-time Services, Threads Interface, Real-time Extensions, Security Interface, Network File Access and Network Process-to-Process Communications, User Portability Extensions, Corrections and Extensions, Protection and Control Utilities and Batch System Utilities. This is POSIX 1003.1-2008 with Technical Corrigendum 1.) POSIX Conformance Testing: A test suite for POSIX accompanies the standard: VSX-PCTS or the VSX POSIX Conformance Test Suite. The development of the POSIX standard takes place in the Austin Group (a joint working group among the IEEE, The Open Group, and the ISO/IEC JTC 1). Versions Parts before 1997 Before 1997, POSIX comprised several standards: POSIX.1: Core Services (incorporates Standard ANSI C) (IEEE Std 1003.1-1988) Process Creation and Control Signals Floating Point Exceptions Segmentation / Memory Violations Illegal Instructions Bus Errors Timers File and Directory Operations Pipes C Library (Standard C) I/O Port Interface and Control Process Triggers POSIX.1b: Real-time extensions (IEEE Std 1003.1b-1993, later appearing as librt—the Realtime Extensions library)) Priority Scheduling Real-Time Signals Clocks and Timers Semaphores Message Passing Shared Memory Asynchronous and Synchronous I/O Memory Locking Interface POSIX.1c: Threads extensions (IEEE Std 1003.1c-1995) Thread Creation, Control, and Cleanup Thread Scheduling Thread Synchronization Signal Handling POSIX.2: Shell and Utilities (IEEE Std 1003.2-1992) Command Interpreter Utility Programs Versions after 1997 After 1997, the Austin Group developed the POSIX revisions. The specifications are known under the name Single UNIX Specification, before they become a POSIX standard when formally approved by the ISO. POSIX.1-2001 (with two TCs) POSIX.1-2001 (or IEEE Std 1003.1-2001) equates to the Single UNIX Specification version 3. This standard consisted of: the Base Definitions, Issue 6, the System Interfaces and Headers, Issue 6, the Commands and Utilities, Issue 6. IEEE Std 1003.1-2004 involved a minor update of POSIX.1-2001. It incorporated two minor updates or errata referred to as Technical Corrigenda (TCs). Its contents are available on the web. POSIX.1-2008 (with two TCs) Base Specifications, Issue 7 (or IEEE Std 1003.1-2008, 2016 Edition) is similar to the current 2017 version (as of 22 July 2018). This standard consists of: the Base Definitions, Issue 7, the System Interfaces and Headers, Issue 7, the Commands and Utilities, Issue 7, the Rationale volume. POSIX.1-2017 IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008) - IEEE Standard for Information Technology—Portable Operating System Interface (POSIX(R)) Base Specifications, Issue 7 is available from either The Open Group or IEEE and is, as of 22 July 2018, the current standard. It is technically identical to POSIX.1-2008 with Technical Corrigenda 1 and 2 applied. A free online copy may still be available. Controversies 512- vs 1024-byte blocks POSIX mandates 512-byte default block sizes for the df and du utilities, reflecting the typical size of blocks on disks. When Richard Stallman and the GNU team were implementing POSIX for the GNU operating system, they objected to this on the grounds that most people think in terms of 1024 byte (or 1 KiB) blocks. The environment variable was introduced to allow the user to force the standards-compliant behaviour. The variable name was later changed to . This variable is now also used for a number of other behaviour quirks. POSIX-oriented operating systems Depending upon the degree of compliance with the standards, one can classify operating systems as fully or partly POSIX compatible. POSIX-certified Current versions of the following operating systems have been certified to conform to one or more of the various POSIX standards. This means that they passed the automated conformance tests and their certification has not expired and the operating system has not been discontinued. AIX EulerOS HP-UX INTEGRITY macOS (since 10.5 Leopard) OpenServer UnixWare VxWorks z/OS Formerly POSIX-certified Some versions of the following operating systems had been certified to conform to one or more of the various POSIX standards. This means that they passed the automated conformance tests. The certification has expired and some of the operating systems have been discontinued. Inspur K-UX IRIX OS/390 QNX Neutrino Solaris Tru64 Mostly POSIX-compliant The following, while not officially certified as POSIX compatible, comply in large part: Android (Available through Android NDK) BeOS (and subsequently Haiku) Contiki Darwin (core of macOS and iOS) DragonFly BSD FreeBSD illumos Linux (most distributions — see Linux Standard Base) LynxOS MINIX (now MINIX3) MPE/iX NetBSD Nucleus RTOS NuttX OpenBSD OpenSolaris PikeOS RTOS for embedded systems with optional PSE51 and PSE52 partitions; see partition (mainframe) Redox RTEMS – POSIX API support designed to IEEE Std. 1003.13-2003 PSE52 Stratus OpenVOS SkyOS Syllable ULTRIX VSTa VMware ESXi Xenix POSIX for Microsoft Windows Cygwin provides a largely POSIX-compliant development and run-time environment for Microsoft Windows. MinGW, a fork of Cygwin, provides a less POSIX-compliant development environment and supports compatible C-programmed applications via Msvcrt, Microsoft's old Visual C runtime library. Microsoft POSIX subsystem, an optional Windows subsystem included in Windows NT-based operating systems up to Windows 2000. POSIX-1 as it stood in 1990 revision, without threads or sockets. Interix, originally OpenNT by Softway Systems, Inc., is an upgrade and replacement for Microsoft POSIX subsystem that was purchased by Microsoft in 1999. It was initially marketed as a stand-alone add-on product and then later included it as a component in Windows Services for UNIX (SFU) and finally incorporated it as a component in Windows Server 2003 R2 and later Windows OS releases under the name "Subsystem for UNIX-based Applications" (SUA); later made deprecated in 2012 (Windows 8) and dropped in 2013 (2012 R2, 8.1). It enables full POSIX compliance for certain Microsoft Windows products. Windows Subsystem for Linux, also known as WSL, is a compatibility layer for running Linux binary executables natively on Windows 10 using a Linux image such as Ubuntu, Debian, or OpenSUSE among others, acting as an upgrade and replacement for Windows Services for UNIX. It was released in beta in April 2016. The first distribution available was Ubuntu. UWIN from AT&T Research implements a POSIX layer on top of the Win32 APIs. MKS Toolkit, originally created for MS-DOS, is a software package produced and maintained by MKS Inc. that provides a Unix-like environment for scripting, connectivity and porting Unix and Linux software to both 32- and 64-bit Microsoft Windows systems. A subset of it was included in the first release of Windows Services for UNIX (SFU) in 1998. Windows C Runtime Library and Windows Sockets API implement commonly used POSIX API functions for file, time, environment, and socket access, although the support remains largely incomplete and not fully interoperable with POSIX-compliant implementations. POSIX for OS/2 Mostly POSIX compliant environments for OS/2: emx+gcc – largely POSIX compliant POSIX for DOS Partially POSIX compliant environments for DOS include: emx+gcc – largely POSIX compliant DJGPP – partially POSIX compliant DR-DOS multitasking core via – a POSIX threads frontend API extension is available Compliant via compatibility layer The following are not officially certified as POSIX compatible, but they conform in large part to the standards by implementing POSIX support via some sort of compatibility feature (usually translation libraries, or a layer atop the kernel). Without these features, they are usually non-compliant. AmigaOS (through ixemul library) eCos – POSIX is part of the standard distribution, and used by many applications. 'external links' section below has more information. IBM i (through the PASE compatibility layer) MorphOS (through the built-in ixemul library) OpenVMS (through optional POSIX package) Plan 9 from Bell Labs APE - ANSI/POSIX Environment RIOT (through optional POSIX module) Symbian OS with PIPS (PIPS Is POSIX on Symbian) Windows NT kernel when using Microsoft SFU 3.5 or SUA Windows 2000 Server or Professional with Service Pack 3 or later. To be POSIX compliant, one must activate optional features of Windows NT and Windows 2000 Server. Windows XP Professional with Service Pack 1 or later Windows Server 2003 Windows Server 2008 and Ultimate and Enterprise versions of Windows Vista Windows Server 2008 R2 and Ultimate and Enterprise versions of Windows 7 albeit deprecated, still available for Windows Server 2012 and Enterprise version of Windows 8 VAXELN (partial support of 1003.1 and 1003.4 through the VAXELN POSIX runtime library) See also POSIX signal POSIX Threads TRON project – alternative OS standards to POSIX Common User Access – User interface standard Interix – a full-featured POSIX and Unix environment subsystem for Microsoft's Windows NT-based operating systems C POSIX library Real-time operating system Portable character set, set of 103 characters which should be supported in any POSIX-compliant character set locale Single UNIX Specification References External links Application programming interfaces Open Group standards IEC standards IEEE standards ISO standards

Operating System (OS)

Open system (computing) Open systems are computer systems that provide some combination of interoperability, portability, and open software standards. (It can also refer to specific installations that are configured to allow unrestricted access by people and/or other computers; this article does not discuss that meaning). The term was popularized in the early 1980s, mainly to describe systems based on Unix, especially in contrast to the more entrenched mainframes and minicomputers in use at that time. Unlike older legacy systems, the newer generation of Unix systems featured standardized programming interfaces and peripheral interconnects; third party development of hardware and software was encouraged, a significant departure from the norm of the time, which saw companies such as Amdahl and Hitachi going to court for the right to sell systems and peripherals that were compatible with IBM's mainframes. The definition of "open system" can be said to have become more formalized in the 1990s with the emergence of independently administered software standards such as The Open Group's Single UNIX Specification. Although computer users today are used to a high degree of both hardware and software interoperability, in the 20th century the open systems concept could be promoted by Unix vendors as a significant differentiator. IBM and other companies resisted the trend for decades, exemplified by a now-famous warning in 1991 by an IBM account executive that one should be "careful about getting locked into open systems". However, in the first part of the 21st century many of these same legacy system vendors, particularly IBM and Hewlett-Packard, began to adopt Linux as part of their overall sales strategy, with "open source" marketed as trumping "open system". Consequently, an IBM mainframe with Linux on IBM Z is marketed as being more of an open system than commodity computers using closed-source Microsoft Windows—or even those using Unix, despite its open systems heritage. In response, more companies are opening the source code to their products, with a notable example being Sun Microsystems and their creation of the OpenOffice.org and OpenSolaris projects, based on their formerly closed-source StarOffice and Solaris software products. See also Open API Open format Open mainframe Open System Environment Reference Model Unix wars References Computer systems History of computing Unix history

Operating System (OS)

Domain/OS Domain/OS is the discontinued operating system used by the Apollo/Domain line of workstations manufactured by Apollo Computer. It was originally launched in 1981 as AEGIS, and was rebranded to Domain/OS in 1988 when Unix environments were added to the operating system. It was one of the early distributed operating systems. Hewlett-Packard supported the operating system for a short time after they purchased Apollo, but they later ended the product line in favor of HP-UX. HP ended final support for Domain/OS on January 1, 2001. AEGIS AEGIS was distinctive mainly for being designed for the networked computer, as distinct from its competitors, which were essentially standalone systems with added network features. The prime examples of this were the file system, which was fully integrated across machines, as opposed to Unix which even now draws a distinction between file systems on the host system and on others, and the user administration system, which was fundamentally network-based. So basic was this orientation that even a standalone Apollo machine could not be configured without a network card. Domain/OS implemented functionality derived from both System V and early BSD Unix systems. It improved on AEGIS by providing a core OS upon which the user could install any or all of three environments: AEGIS, System V Unix, and BSD Unix. This was done in order to provide greater compatibility with Unix; AEGIS version SR9, which immediately preceded Domain/OS (itself numbered SR10) had had an optional product called Domain/IX available, which provided a similar capability, but with some drawbacks, principally the fact that core administrative tasks still required AEGIS commands. Also, the SR9 permissions system was not fully compatible with Unix behaviour. Domain/OS provided new administrative commands and a more complex permissions system which could be configured to behave properly under any of the three environments. Domain/OS also provided an improved version of the X Window System, complete with VUE (HP's predecessor to CDE), but performance tended to be poor. User upgrading from AEGIS SR9 to Domain/OS SR10 was slowed by the fact that many users saw no requirement; by increased disk space requirements; by new and more complex administration tools; by SR10's poorer performance; and by the buggy nature of SR10.0, although later versions were much more reliable. However, later HP/Apollo machines (the DN10000, DN2500 and 4xx series workstations) could only run SR10. Unlike many operating systems of the day, which were written in C or assembly language, many Domain/OS components were written in Pascal. Compilers for users were available for C, C++, Pascal, and Fortran. All of the distributed administration features of Domain/OS were built around a remote procedure call system called NCS RPC. Though RPC was later end-of-lifed with the operating system, HP contributed RPC to the Open Software Foundation, which incorporated its Interface Definition Language (IDL) into their DCE product, from which the same technology was later used for CORBA. One of the original developers went to work for Microsoft, where he developed MSRPC as a fairly compatible clone which today forms a central component of Windows systems. Traces of the history can be seen to this day in protocol names such as ncacn_http. User interface AEGIS was similar to other workstations of the time, in that it used a high-resolution graphics screen and mouse to provide a GUI named DM (Display Manager). DM was integrated with the operating system's own window manager known as wmgr (Window Manager). The DM contained two built-in functions, a text editor and a transcript, which is a kind of virtual terminal. Additional functions could be added by user programs. One of the unique features of the DM was "universal editing". All text in any of the built-in windows could be edited using the same editing language. This included the history displayed in a transcript window, although that text was read-only. In addition, the history was unbounded. It started from the birth of the process to which it was attached, and older history was never deleted, as it is in all virtual terminals today. Another interesting feature was that each transcript was attached to a mini-input window where the process input could be edited using the same editing language used elsewhere. The AEGIS command interface was similar to Unix, in that it had a command line interpreter which understood pipes, redirection, scripting, etc., and invoked other commands as separate programs, but the actual commands themselves were designed to be easier to remember and use than their sometimes cryptic Unix equivalents, and wildcards were expected to be expanded by individual commands rather than by the command line interpreter itself. One noticeable and very useful feature was the ability to embed environment variables in symbolic links, which, for example, allowed the user to switch between different versions of Unix simply by setting the SYSTYPE environment variable accordingly; symbolic links then pointed to the correct versions of the files. History Domain/OS incorporated several ideas from Multics, including single-level store and dynamic linking. See also Timeline of operating systems References Further reading DOMAIN System User's Guide. Apollo Computer Inc., 2nd. ed., 1987 External links Apollo DomainOS info and archive Apollo Frequently Asked Questions Apollo/DOMAIN Computers Distributed operating systems Discontinued operating systems HP software Multics-like Unix variants 1981 software

Operating System (OS)

Windows NT Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system. The first version of Windows NT was Windows NT 3.1 and was produced for workstations and server computers. It was a commercially focused operating system intended to complement consumer versions of Windows that were based on MS-DOS (including Windows 1.0 through Windows 3.1x). Gradually, the Windows NT family was expanded into Microsoft's general-purpose operating system product line for all personal computers, deprecating the Windows 9x family. "NT" was formerly expanded to "New Technology" but no longer carries any specific meaning. Starting with Windows 2000, "NT" was removed from the product name and is only included in the product version string along with several low-level places within the system. NT was the first purely 32-bit version of Windows, whereas its consumer-oriented counterparts, Windows 3.1x and Windows 9x, were 16-bit/32-bit hybrids. It is a multi-architecture operating system. Initially, it supported several instruction set architectures, including IA-32, MIPS, and DEC Alpha; support for PowerPC, Itanium, x64, and ARM were added later. The latest versions support x86 (including IA-32 and x64) and ARM. Major features of the Windows NT family include Windows Shell, Windows API, Native API, Active Directory, Group Policy, Hardware Abstraction Layer, NTFS, BitLocker, Windows Store, Windows Update, and Hyper-V. Naming It has been suggested that Dave Cutler intended the initialism "WNT" as a play on VMS, incrementing each letter by one. However, the project was originally intended as a follow-on to OS/2 and was referred to as "NT OS/2" before receiving the Windows brand. One of the original NT developers, Mark Lucovsky, states that the name was taken from the original target processor—the Intel i860, code-named N10 ("N-Ten"). A 1998 question-and-answer (Q&A) session with Bill Gates revealed that the letters were previously expanded to "New Technology" but no longer carry any specific meaning. The letters were dropped from the names of releases from Windows 2000 and later, though Microsoft described that product as being "Built on NT Technology". Major features One of the main purposes of NT is hardware and software portability. Various versions of NT family operating systems have been released for a variety of processor architectures, initially IA-32, MIPS, and DEC Alpha, with PowerPC, Itanium, x86-64 and ARM supported in later releases. An initial idea was to have a common code base with a custom Hardware Abstraction Layer (HAL) for each platform. However, support for MIPS, Alpha, and PowerPC was later dropped in Windows 2000. Broad software compatibility was initially achieved with support for several API "personalities", including Windows API, POSIX, and OS/2 APIs – the latter two were phased out starting with Windows XP. Partial MS-DOS and Windows 16-bit compatibility is achieved on IA-32 via an integrated DOS Virtual Machine – although this feature is not available on other architectures. NT has supported per-object (file, function, and role) access control lists allowing a rich set of security permissions to be applied to systems and services. NT has also supported Windows network protocols, inheriting the previous OS/2 LAN Manager networking, as well as TCP/IP networking (for which Microsoft used to implement a TCP/IP stack derived at first from a STREAMS-based stack from Spider Systems, then later rewritten in-house). Windows NT 3.1 was the first version of Windows to use 32-bit flat virtual memory addressing on 32-bit processors. Its companion product, Windows 3.1, used segmented addressing and switches from 16-bit to 32-bit addressing in pages. Windows NT 3.1 featured a core kernel providing a system API, running in supervisor mode (ring 0 in x86; referred to in Windows NT as "kernel mode" on all platforms), and a set of user-space environments with their own APIs which included the new Win32 environment, an OS/2 1.3 text-mode environment and a POSIX environment. The full preemptive multitasking kernel could interrupt running tasks to schedule other tasks, without relying on user programs to voluntarily give up control of the CPU, as in Windows 3.1 Windows applications (although MS-DOS applications were preemptively multitasked in Windows starting with Windows/386). Notably, in Windows NT 3.x, several I/O driver subsystems, such as video and printing, were user-mode subsystems. In Windows NT 4, the video, server, and printer spooler subsystems were moved into kernel mode. Windows NT's first GUI was strongly influenced by (and programmatically compatible with) that from Windows 3.1; Windows NT 4's interface was redesigned to match that of the brand new Windows 95, moving from the Program Manager to the Windows shell design. NTFS, a journaled, secure file system, is a major feature for NT. Windows NT also allows for other installable file systems; since versions 3.1, NT may be installed on FAT or HPFS file systems. Windows NT introduced its own driver model, the Windows NT driver model, and is incompatible with older driver frameworks. With Windows 2000, the Windows NT driver model was enhanced to become the Windows Driver Model, which was first introduced with Windows 98, but was based on the NT driver model. Windows Vista added native support for the Windows Driver Foundation, which is also available for Windows XP, Windows Server 2003 and to an extent, Windows 2000. Development Microsoft decided to create a portable operating system, compatible with OS/2 and POSIX and supporting multiprocessing, in October 1988. When development started in November 1989, Windows NT was to be known as OS/2 3.0, the third version of the operating system developed jointly by Microsoft and IBM. To ensure portability, initial development was targeted at the Intel i860XR RISC processor, switching to the MIPS R3000 in late 1989, and then the Intel i386 in 1990. Microsoft also continued parallel development of the DOS-based and less resource-demanding Windows environment, resulting in the release of Windows 3.0 in May 1990. Windows 3.0 was eventually so successful that Microsoft decided to change the primary application programming interface for the still unreleased NT OS/2 (as it was then known) from an extended OS/2 API to an extended Windows API. This decision caused tension between Microsoft and IBM and the collaboration ultimately fell apart. IBM continued OS/2 development alone while Microsoft continued work on the newly renamed Windows NT. Though neither operating system would immediately be as popular as Microsoft's MS-DOS or Windows products, Windows NT would eventually be far more successful than OS/2. Microsoft hired a group of developers from Digital Equipment Corporation led by Dave Cutler to build Windows NT, and many elements of the design reflect earlier DEC experience with Cutler's VMS, VAXELN and RSX-11, but also an unreleased object-based operating system developed by Dave Cutler at Digital codenamed MICA. The team was joined by selected members of the disbanded OS/2 team, including Moshe Dunie. The VMS kernel was primarily written in VAX MACRO, but Windows NT was designed to run on multiple instruction set architectures and multiple hardware platforms within each architecture. The platform dependencies are hidden from the rest of the system by the HAL (Hardware Abstraction Layer). While creating Windows NT, Microsoft developers rewrote VMS in C. Although they added the Win32 API, NTFS file system, GUI, and backwards compatibility with DOS, OS/2, and Win16, DEC engineers almost immediately noticed the two operating systems' internal similarities; parts of VAX/VMS Internals and Data Structures, published by Digital Press, accurately describe Windows NT internals using VMS terms. Instead of a lawsuit, Microsoft agreed to pay DEC $65–100 million, help market VMS, train Digital personnel on Windows NT, and continue Windows NT support for DEC Alpha. Windows NT and VMS memory management, processes, and scheduling are very similar. Windows NT's process management differs by implementing threading, which DEC did not implement until VMS 7.0 in 1995, likely to compete with Microsoft. Like VMS, Windows NT's kernel mode code distinguishes between the "kernel", whose primary purpose is to implement processor- and architecture-dependent functions, and the "executive". This was designed as a modified microkernel, as the Windows NT kernel was influenced by the Mach microkernel developed by Richard Rashid at Carnegie Mellon University, but does not meet all of the criteria of a pure microkernel. Both the kernel and the executive are linked together into the single loaded module ntoskrnl.exe; from outside this module, there is little distinction between the kernel and the executive. Routines from each are directly accessible, as for example from kernel-mode device drivers. API sets in the Windows NT family are implemented as subsystems atop the publicly undocumented "native" API; this allowed the late adoption of the Windows API (into the Win32 subsystem). Windows NT was one of the earliest operating systems to use Unicode internally. Releases Windows NT 3.1 to 3.51 incorporated the Program Manager and File Manager from the Windows 3.1x series. Windows NT 4.0 onwards replaced those programs with Windows Explorer (including a taskbar and Start menu), which originally appeared in Windows 95. The first release was given version number 3.1 to match the contemporary 16-bit Windows; magazines of that era claimed the number was also used to make that version seem more reliable than a ".0" release. Also the Novell IPX protocol was apparently licensed only to 3.1 versions of Windows software. The NT version number is not now generally used for marketing purposes, but is still used internally, and said to reflect the degree of changes to the core of the operating system. However, for application compatibility reasons, Microsoft kept the major version number as 6 in releases following Vista, but changed it later to 10 in Windows 10. The build number is an internal identifier used by Microsoft's developers and beta testers. Starting with Windows 8.1, Microsoft changed the Version API Helper functions' behavior. If an application is not manifested for Windows 8.1 or later, the API will always return version 6.2, which is the version number of Windows 8. This is because the manifest feature was introduced with Windows 8.1, to replace GetVersion and related functions. Programming language Windows NT is written in C and C++, with a very small amount written in assembly language. C is mostly used for the kernel code while C++ is mostly used for user-mode code. Assembly language is avoided where possible because it would impede portability. Supported platforms 32-bit platforms In order to prevent Intel x86-specific code from slipping into the operating system by developers used to developing on x86 chips, Windows NT 3.1 was initially developed using non-x86 development systems and then ported to the x86 architecture. This work was initially based on the Intel i860-based Dazzle system and, later, the MIPS R4000-based Jazz platform. Both systems were designed internally at Microsoft. Windows NT 3.1 was released for Intel x86 PC compatible, PC-98, DEC Alpha, and ARC-compliant MIPS platforms. Windows NT 3.51 added support for the PowerPC processor in 1995, specifically PReP-compliant systems such as the IBM Power Series desktops/laptops and Motorola PowerStack series; but despite meetings between Michael Spindler and Bill Gates, not on the Power Macintosh as the PReP compliant Power Macintosh project failed to ship. Intergraph Corporation ported Windows NT to its Clipper architecture and later announced an intention to port Windows NT 3.51 to Sun Microsystems' SPARC architecture, in conjunction with the company's planned introduction of UltraSPARC models in 1995, but neither version was sold to the public as a retail product. Only two of the Windows NT 4.0 variants (IA-32 and Alpha) have a full set of service packs available. All of the other ports done by third parties (Motorola, Intergraph, etc.) have few, if any, publicly available updates. Windows NT 4.0 was the last major release to support Alpha, MIPS, or PowerPC, though development of Windows 2000 for Alpha continued until August 1999, when Compaq stopped support for Windows NT on that architecture; and then three days later Microsoft also canceled their AlphaNT program, even though the Alpha NT 5 (Windows 2000) release had reached RC1 status. On January 5, 2011, Microsoft announced that the next major version of the Windows NT family will include support for the ARM architecture. Microsoft demonstrated a preliminary version of Windows (version 6.2.7867) running on an ARM-based computer at the 2011 Consumer Electronics Show. This eventually led to the commercial release of the Windows 8-derived Windows RT on October 26, 2012, and the implementation of NT over CE on Windows Phone 8. According to Microsoft, it is a common misconception that the Xbox and Xbox 360 use a modified Windows 2000 kernel. In reality, the Xbox operating system was built from scratch but implements a subset of Windows APIs. The Xbox One, and Xbox Series X/S, however, do use a modified version of Windows 10. Windows 11 is the first non-server version of Windows NT to not support 32-bit platforms. 64-bit platforms The 64-bit versions of Windows NT were originally intended to run on Itanium and DEC Alpha; the latter was used internally at Microsoft during early development of 64-bit Windows. This continued for some time after Microsoft publicly announced that it was cancelling plans to ship 64-bit Windows for Alpha. Because of this, Alpha versions of Windows NT are 32-bit only. While Windows 2000 only supports Intel IA-32 (32-bit), Windows XP, Server 2003, Server 2008 and Server 2008 R2 each have one edition dedicated to Itanium-based systems. In comparison with Itanium, Microsoft adopted x64 on a greater scale: every version of Windows since Windows XP (which has a dedicated x64 edition) has x64 editions. Hardware requirements The minimum hardware specification required to run each release of the professional workstation version of Windows NT has been fairly slow-moving until the 6.0 Vista release, which requires a minimum of 15 GB of free disk space, a 10-fold increase in free disk space alone over the previous version. See also Architecture of Windows NT F6 disk Windows Server domain ReactOS (an open source project with the goal of providing binary- and device driver-level compatibility with Windows NT) Windows NT startup process Windows Preinstallation Environment Microsoft Servers Notes References External links . . . 1993 software NT Advanced RISC Computing

Operating System (OS)

A2 (operating system) A2 (formerly named Active Object System (AOS), and then Bluebottle) is a modular, object-oriented operating system, with some unconventional features, including automatic garbage-collected memory management, and a zooming user interface. It was developed originally at ETH Zurich in 2002. It is free and open-source software under a BSD-like license. History A2 is the next generation of Native Oberon, the x86 PC version of Niklaus Wirth's operating system Oberon. It is small, fast, supports multiprocessing computers, and provides soft real-time computing operation. It is entirely written in an upward-compatible dialect of the programming language Oberon named Active Oberon. Both languages are members of the Pascal family, along with Modula-2. A2's design allows developing efficient systems based on active objects which run directly on hardware, with no mediating interpreter or virtual machine. Active objects represent a combination of the traditional object-oriented programming (OOP) model of an object, combined with a thread that executes in the context of that object. In the Active Oberon implementation, an active object may include activity of its own, and of its ancestor objects. Other differences between A2 and more mainstream operating systems is a very minimalist design, completely implemented in a type-safe language, with automatic memory management, combined with a powerful and flexible set of primitives (at the level of programming language and runtime system) for synchronising access to the internal properties of objects in competing execution contexts. Above the kernel layer, A2 provides a flexible set of modules providing unified abstractions for devices and services, such as file systems, user interfaces, computer network connections, media codecs, etc. User interface Bluebottle replaced the older Oberon OS's unique text-based user interface (TUI) with a zooming user interface (ZUI), which is significantly more like a conventional graphical user interface (GUI). Like Oberon, though, its user interface supports a point and click interface metaphor to execute commands directly from text, similar to clicking hyperlinks in a web browser. See also Oberon (operating system) Oberon (programming language) Oberon-2 programming language Minimalism (computing) References External links , ETH Zürich Oberon Language Genealogy Bluebottle Home Page running on Bluebottle machine Oberon Community Platform - Wiki & Forum An application in industrial control at Radiar A short movie showing a programming technique and the Bluebottle OS Free software operating systems

Operating System (OS)

Atari TOS TOS (The Operating System) is the operating system of the Atari ST range of computers. This range includes the 520ST and 1040ST, their STF/M/FM and STE variants and the Mega ST/STE. Later, 32-bit machines (TT, Falcon030) were developed using a new version of TOS, called MultiTOS, which allowed multitasking. More recently, users have further developed TOS into FreeMiNT. Details The Atari TOS (The Operating System) debuted with the Atari 520ST in 1985. TOS combines Digital Research's GEM GUI running on top of the DOS-like GEMDOS. Features include a flat memory model, DOS-compatible disk format (starting with TOS 1.04), support for MIDI, and a variant of SCSI called ACSI in later versions. Atari's TOS is usually run from ROM chips contained in the computer: Thus, before local hard drives were available in home computers, it was an almost instant-running OS. TOS booted off floppy disks in the very first STs, but only about half a year after the ST was introduced, all ST models started shipping with the latest version of TOS in ROM. TOS consisted of the following: Desktop – The main interface loaded after bootup. GEM – Graphics Environment Manager, licensed from Digital Research AES – Application Environment Services VDI – Virtual Device Interface (screen drivers only, other drivers loaded using GDOS) GEMDOS – GEM Disk Operating System BIOS – Basic Input/Output System XBIOS – Extended BIOS Line-A – Low-level high-speed graphics calls. Obsolete. The following were extensions to TOS (loaded separately): GDOS – Graphics Device Operating System AHDI – Atari Hard Disk Interface (hard disk driver) True multitasking was not directly supported, but TOS allowed up to six desk accessories to be loaded into the system, which are similar to TSRs (Terminate and Stay Resident programs) on PCs. MultiTOS was developed to allow TOS to preemptively multitask. Desktop The TOS desktop uses icons to represent files and devices, windows and dialog boxes to display info. The desktop file "DESKTOP.INF" was read to determine window settings, icon placements and drive icons, otherwise the standard default desktop of two floppy icons and the trash icon was used. Later versions use "NEWDESK.INF" for saving and reading the desktop configuration. Executable files are identified by their extensions: *.ACC – Desktop accessory. Automatically loaded. *.APP – Application (rarely encountered). *.PRG – Executable program. Can be GEM programs. *.TOS – "TOS" program that doesn't use GEM — i.e., similar to a PC's .EXE or .COM running in a CLI-mode box. The desktop clears the screen, turns on the text cursor, and hides the mouse pointer. *.TTP – "TOS takes parameters". This opens a dialog box where arguments can be added for the program. It converts characters to uppercase. *.GTP – "GEM takes parameters". This opens a dialog box where arguments can be added for the program. It converts characters to uppercase. TOS programs (but not GEM programs) can auto boot by placing them in a folder named "AUTO". TOS 1.4 allows GEM programs to be set to load automatically from the "Install Application" dialog. Programs with *.TTP extensions and environments can not be used for auto boot. Desktop accessories were placed in the root directory of the default drive and loaded automatically. File system Atari TOS is based on GEMDOS which uses a modified FAT12 (or, on hard disks, FAT16) file system. The major differences are the fact that the boot sector does not need to contain the IBM compatible jump sequence at the beginning (typically or ), the lack (before TOS 1.04) of an OEM identifier compatible with PC-based systems, and the fact that a checksum is used to mark the boot sector as executable (the PC format uses the signature word instead). Executable boot sectors for the Atari platform typically start with an MC68K jump opcode (e.g. , and the last two byte word must sum with the rest of the boot sector (in big-endian word form) to in order to be bootable. Unlike MS-DOS, GEMDOS would typically allow disks with unusual sector and track counts, so disks with 10 or even 11 sectors per track and over 80 formatted tracks were not uncommon in the Atari community. Typically a safe combination, such as 10 sectors per track by 80 tracks, was used, yielding an unformatted capacity of 800KB, but many users pushed the capacity of their double-density disks beyond 900KB using custom formats. GEMDOS disc file systems can be read using DOS or Windows 9x. Versions TOS 1 1.0 (ROM TOS) Earliest version released on disk. First ROM release of TOS. Formats: floppy, 2 chip and 6 chip ROMs (192 KB) ROM date: 20 November 1985 Machines: 520ST, 1040ST 1.02 (MEGA TOS) fixed bugs, supported Blitter co-processor and real-time clock. Formats: 2 chip and 6 chip ROMs (192 KB) ROM date: 22 April 1987 Machines: 520ST, 1040ST, Mega 1, Mega 2, Mega 4 1.04 (RAINBOW TOS) Many bug fixes, file selector changed, DOS-compatible disk formatting, much improved performance. However, compatibility problems with older software. Formats: 2 chip and 6 chip ROMs (192 KB) ROM date: 6 April 1989 Machines: 520ST, 1040ST, Mega 1, Mega 2, Mega 4, Stacy 1.06 (STE TOS, Revision 1) Support for STe machines only. Needed STE_FIX.PRG to patch bugs. Format: 2 chip ROMs (256 KB) ROM date: 29 July 1989 Machines: 520STE, 1040 STE 1.62 (STE TOS, Revision 2) bug fixes for the previous 1.06 STE TOS. Format: 2 chip ROMs (256 KB) ROM date: 1 January 1990 Machines: 520STE, 1040 STE TOS 2 2.02 Early TOS release for Mega STE. 2.05 (Mega STE TOS) Only found in the Mega STE with 720K floppy drive. Format: 2 chip ROMs (256 KB) ROM date: 5 December 1990 Machines: Mega STE 2.06 (ST/STE TOS) Last TOS version for ST/STE computers. Bug fixes, 1.44 MB disk support, memory test. Adds GTP program support (GEM-Takes-Parameters). Greatly enhanced GEM GUI. IDE hard disk booting. Atari logo display at boot-up. Automatic cold boot memory test. Supports higher resolutions. Format: 2 chip ROMs (256 KB) ROM date: 14 November 1991 Machines: 520ST, 1040ST, 520STE, 1040STE 2.07 used on the Falcon prototype "FX-1" 2.08 used in notebook ST. ROM also contains some notebook-specific utilities: STTRANS (null-modem/ parallel-cable data transfer), power management tools, hard disk drive tools and drivers (AHDI, XHDI, BOOKINST and BOOKFMT) and a RAMdisk installer. TOS 3 3.01, 3.05, 3.06 (TT TOS) Primarily for 68030 TT support only. Supports fast "TT RAM", special TT screen resolutions etc. ST-hardware-compatible "Line-A" API dropped for extended TT functionality, forcing programmers to use GEM-compliant VDI calls etc. and thus encouraging GEM-compatible (as opposed to ST-compatible) development. Format: 4 chip ROMs (512 KB) TOS 4 4.00, 4.01, 4.02, 4.04 (512 KB) Update for Falcon 030 machines only. 68030 only. Adds support for DSP, 16 MHz blitter and video overlay. New v3.40 AES (last single-tasking version, but MiNT/MultiTOS-multitasking-aware) supports: pop-up menus, 3D window and dialog objects (later modified to use more compatible ob_state flags instead of extended type), 256-colour "animated" icons, soft-loaded fonts, inter-app drag&drop, background window manipulation, extensible filesystems. New CPX module for international localisation configuration. V4.04 was the last official Atari version of TOS. 4.08 (512 KB) Developed and released by Milan Computersysteme for the Milan, a 68040/60 TOS/GEM computer. 4.9x (4.92, 4.98) Never officially released, though prototypes were leaked and subsequently shared. TOS 4.92 was a version of MultiTOS, the multitasking version of TOS, in a format (.IMG) designed to be written to a ROM chip. TOS 4 ROM contains five user-selectable language versions. See also EmuTOS Multitasking versions of TOS MiNT MagiC MultiTOS GEM Atari ST character set References External links tos.hyp - a reference about the system api of TOS, MultiTOS, MagiC and MagiCMac Town's Guide to TOS Revisions ATARIworld Atari ST System Disks ATARI Document Archive TOS 2.06 Guide – User's guide Atari operating systems TOS Disk operating systems Discontinued operating systems Window-based operating systems 1985 software

Operating System (OS)

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to manufacturing on May 15, 1998, and generally to retail on June 25, 1998. Like its predecessor, it is a hybrid 16-bit and 32-bit monolithic product with the boot stage based on MS-DOS. Windows 98 is a heavily web-integrated operating system that bears numerous similarities to its predecessor and relies on the HTML language. Most of its improvements were cosmetic or designed to improve the user experience, but there were also a handful of features introduced to enhance system functionality and capabilities, including improved USB support and accessibility, as well as support for hardware advancements such as DVD players. Windows 98 was the first edition of Windows to adopt the Windows Driver Model, and introduced features that would become standard in future generations of Windows, such as Disk Cleanup, Windows Update, multi-monitor support, and Internet Connection Sharing. Microsoft had marketed Windows 98 as a "tune-up" to Windows 95, rather than an entirely improved next generation of Windows. Upon release, it was generally well-received for its web-integrated interface and ease of use, as well as its addressing of issues present in Windows 95, although some pointed out that it was not significantly more stable than its predecessor. Windows 98 sold an estimated 58 million licenses, and saw one major update, known as Windows 98 Second Edition (SE), released on May 5, 1999. After the release of its successor, Windows Me in 2000, mainstream support for Windows 98 and 98 SE ended on June 30, 2002, followed by extended support on July 11, 2006. Development Following the success of Windows 95, development of Windows 98 began, initially under the development codename "Memphis." The first test version, Windows Memphis Developer Release, was released in January 1997. Memphis first entered beta as Windows Memphis Beta 1, released on June 30, 1997. It was followed by Windows 98 Beta 2, which dropped the Memphis name and was released in July. Microsoft had planned a full release of Windows 98 for the first quarter of 1998, along with a Windows 98 upgrade pack for Windows 95, but it also had a similar upgrade for Windows 3.x operating systems planned for the second quarter. Stacey Breyfogle, a product manager for Microsoft, explained that the later release of the upgrade for Windows 3 was because the upgrade required more testing than that for Windows 95 due to the presence of more compatibility issues, and without user objections, Microsoft merged the two upgrade packs into one and set all of their release dates to the second quarter. On December 15, Microsoft released Windows 98 Beta 3. It was the first build to be able to upgrade from Windows 3.1x, and introduced new startup and shutdown sounds. Near its completion, Windows 98 was released as Windows 98 Release Candidate on April 3, 1998, which expired on December 31. This coincided with a notable press demonstration at COMDEX that month. Microsoft CEO Bill Gates was highlighting the operating system's ease of use and enhanced support for Plug and Play (PnP). However, when presentation assistant Chris Capossela plugged a USB scanner in, the operating system crashed, displaying a Blue Screen of Death. Bill Gates remarked after derisive applause and cheering from the audience, "That must be why we're not shipping Windows 98 yet." Video footage of this event became a popular Internet phenomenon. Microsoft had quietly marketed the operating system as a "tune-up" to Windows 95. It was compiled as Windows 98 on May 11, 1998, before being fully released to manufacturing on May 15. The company was facing pending legal action for allowing free downloads of, and planning to ship Windows licenses with, Internet Explorer 4.0 in an alleged effort to expand its software monopoly. Microsoft's critics believed the lawsuit would further delay Windows 98's public release; it did not, and the operating system was released on June 25, 1998. A second major version of the operating system called Windows 98 Second Edition was later unveiled in March 1999. Microsoft compiled the final build on April 23, 1999, before publicly releasing it on May 5, 1999. Windows 98 was to be the final product in the Windows 9x line until Microsoft briefly revived the line to release Windows Me in 2000 as the final Windows 9x product before the introduction of Windows XP in 2001. New and updated features Web integration and shell enhancements The first release of Windows 98 included Internet Explorer 4.01. This was updated to 5.0 in the Second Edition. Besides Internet Explorer, many other Internet companion applications are included such as Outlook Express, Windows Address Book, FrontPage Express, Microsoft Chat, Personal Web Server and a Web Publishing Wizard, and NetShow. NetMeeting allows multiple users to hold conference calls and work with each other on a document. The Windows 98 shell is web-integrated; it contains deskbands, Active Desktop, Channels, ability to minimize foreground windows by clicking their button on the taskbar, single-click launching, Back and Forward navigation buttons, favorites, and address bar in Windows Explorer, image thumbnails, folder infotips and Web view in folders, and folder customization through HTML-based templates. The taskbar supports customizable toolbars designed to speed up access to the Web or the user's desktop; these toolbars include an Address Bar and Quick Launch. With the Address Bar, the user accesses the Web by typing in a URL, and Quick Launch contains shortcuts or buttons that perform system functions such as switching between windows and the desktop with the Show Desktop button. Another feature of this new shell is that dialog boxes show up in the Alt-Tab sequence. Windows 98 also integrates shell enhancements, themes and other features from Microsoft Plus! for Windows 95 such as DriveSpace 3, Compression Agent, Dial-Up Networking Server, Dial-Up Scripting Tool and Task Scheduler. 3D Pinball Space Cadet is included on the CD-ROM, but not installed by default. Windows 98 had its own separately purchasable Plus! pack, called Plus! 98. Title bars of windows and dialog boxes support two-color gradients, a feature ported from and refined from Microsoft Office 95. Windows menus and tooltips support slide animation. Windows Explorer in Windows 98, as in Windows 95, converts all-uppercase filenames to sentence case for readability purposes; however, it also provides an option Allow all uppercase names to display them in their original case. Windows Explorer includes support for compressed CAB files. The Quick Res and Telephony Location Manager Windows 95 PowerToys are integrated into the core operating system. Improvements to hardware support Windows Driver Model Windows 98 was the first operating system to use the Windows Driver Model (WDM). This fact was not well publicized when Windows 98 was released, and most hardware producers continued to develop drivers for the older VxD driver standard, which Windows 98 supported for compatibility's sake. The WDM standard only achieved widespread adoption years later, mostly through Windows 2000 and Windows XP, as they were not compatible with the older VxD standard. With the Windows Driver Model, developers could write drivers that were compatible with other versions of Windows. Device driver access in WDM is actually implemented through a VxD device driver, NTKERN.VXD, which implements several Windows NT-specific kernel support functions. Support for WDM audio enables digital mixing, routing and processing of simultaneous audio streams and kernel streaming with high quality sample rate conversion on Windows 98. WDM Audio allows for software emulation of legacy hardware to support MS-DOS games, DirectSound support and MIDI wavetable synthesis. The Windows 95 11-device limitation for MIDI devices is eliminated. A Microsoft GS Wavetable Synthesizer licensed from Roland shipped with Windows 98 for WDM audio drivers. Windows 98 supports digital playback of audio CDs, and the Second Edition improves WDM audio support by adding DirectSound hardware mixing and DirectSound 3D hardware abstraction, DirectMusic kernel support, KMixer sample-rate conversion for capture streams and multichannel audio support. All audio is sampled by the Kernel Mixer to a fixed sampling rate which may result in some audio getting upsampled or downsampled and having a high latency, except when using Kernel Streaming or third-party audio paths like ASIO which allow unmixed audio streams and lower latency. Windows 98 also includes a WDM streaming class driver (Stream.sys) to address real time multimedia data stream processing requirements and a WDM kernel-mode video transport for enhanced video playback and capture. Windows Driver Model also includes Broadcast Driver Architecture, the backbone for TV technologies support in Windows. WebTV for Windows utilized BDA to allow viewing television on the computer if a compatible TV tuner card is installed. TV listings could be updated from the Internet and WaveTop Data Broadcasting allowed extra data about broadcasts to be received via regular television signals using an antenna or cable, by embedding data streams into the vertical blanking interval portion of existing broadcast television signals. Other device support improvements Windows 98 had more robust USB support than Windows 95, which only had support in OEM versions OSR2.1 and later. Windows 98 supports USB hubs, USB scanners and imaging class devices. Windows 98 also introduced built-in support for some USB Human Interface Device class (USB HID) and PID class devices such as USB mice, keyboards, force feedback joysticks etc. including additional keyboard functions through a certain number of Consumer Page HID controls. Windows 98 introduced ACPI 1.0 support which enabled Standby and Hibernate states. However, hibernation support was extremely limited, and vendor-specific. Hibernation was only available if compatible (PnP) hardware and BIOS are present, and the hardware manufacturer or OEM supplied compatible WDM drivers, non-VxD drivers. However, there are hibernation issues with the FAT32 file system, making hibernation problematic and unreliable. Windows 98, in general, provides improved — and a broader range of — support for IDE and SCSI drives and drive controllers, floppy drive controllers and all other classes of hardware as compared to Windows 95. There is integrated Accelerated Graphics Port (AGP) support (although the USB Supplement to Windows 95 OSR2 and later releases of Windows 95 did have AGP support). Windows 98 has built-in DVD support and UDF 1.02 read support. The Still imaging architecture (STI) with TWAIN support was introduced for scanners and cameras and Image Color Management 2.0 for devices to perform color space transformations. Multiple monitor support allows using up to nine multiple monitors on a single PC, with the feature requiring one PCI graphics adapter per monitor. Windows 98 shipped with DirectX 5.2, which notably included DirectShow. Windows 98 Second Edition would later ship with DirectX 6.1. Networking enhancements Windows 98 networking enhancements to TCP/IP include built-in support for Winsock 2, SMB signing, a new IP Helper API, Automatic Private IP Addressing (also known as link-local addressing), IP multicasting, and performance enhancements for high-speed high bandwidth networks. Multihoming support with TCP/IP is improved and includes RIP listener support. The DHCP client has been enhanced to include address assignment conflict detection and longer timeout intervals. NetBT configuration in the WINS client has been improved to continue persistently querying multiple WINS servers if it failed to establish the initial session until all of the WINS servers specified have been queried or a connection is established. Network Driver Interface Specification 5 support means Windows 98 can support a wide range of network media, including Ethernet, Fiber Distributed Data Interface (FDDI), Token Ring, Asynchronous Transfer Mode (ATM), ISDN, wide area networks, X.25, and Frame Relay. Additional features include NDIS power management, support for quality of service, Windows Management Instrumentation (WMI) and support for a single INF file format across all Windows versions. Windows 98 Dial-Up Networking supports PPTP tunneling, support for ISDN adapters, multilink support, and connection-time scripting to automate non-standard login connections. Multilink channel aggregation enables users to combine all available dial-up lines to achieve higher transfer speeds. PPP connection logs can show actual packets being passed and Windows 98 allows PPP logging per connection. The Dial-Up Networking improvements are also available in Windows 95 OSR2 and are downloadable for earlier Windows 95 releases. For networked computers that have user profiles enabled, Windows 98 introduces Microsoft Family Logon which lists all users that have been configured for that computer, enabling users to simply select their names from a list rather than having to type them in. Windows 98 supports IrDA 3.0 that specifies both Serial Infrared Devices and Fast Infrared devices, which are capable of sending and receiving data at 4 Mbit/s. Infrared Recipient, a new application for transferring files through an infrared connection is included. The IrDA stack in Windows 98 supports networking profiles over the IrCOMM kernel-mode driver. Windows 98 also has built-in support for browsing Distributed File System trees on Server Message Block shares such as Windows NT servers. UPnP and NAT traversal APIs can be installed on Windows 98 by installing the Windows XP Network Setup Wizard. An L2TP/IPsec VPN client can also be downloaded. By installing Active Directory Client Extensions, Windows 98 can take advantage of several Windows 2000 Active Directory features. Improvements to the system and built-in utilities Performance improvements Windows 95 introduced the 32-bit, protected-mode cache driver VCACHE (replacing SMARTDrv) to cache the most recently accessed information from the hard drive in memory, divided into chunks. However, the cache parameters needed manual tuning as it degraded performance by consuming too much memory and not releasing it quickly enough, forcing paging to occur far too early. The Windows 98 VCACHE cache size management for disk and network access, CD-ROM access and paging is more dynamic compared to Windows 95, resulting in no tuning being required for cache parameters. On the FAT32 file system, Windows 98 has a performance feature called MapCache that can run applications from the disk cache itself if the code pages of executable files are aligned/mapped on 4K boundaries, instead of copying them to virtual memory. This results in more memory being available to run applications, and lesser usage of the swap file. Windows 98 registry handling is more robust than Windows 95 to avoid corruption and there are several enhancements to eliminate limitations and improve registry performance. The Windows 95 registry key size limitation of 64 KB is gone. The registry uses less memory and has better caching. Disk Defragmenter has been improved to rearrange program files that are frequently used to a hard disk region optimized for program start. The aggravating "Drive contents changed....restarting." message will still frequently appear in this version. If it gets stuck on the same area too many times, it will ask the user if it should keep trying or give up. However, the Disk Defragmenter from Windows Me does not have this problem and will function on Windows 98 if the user copies it over. Windows 98 also supports a Fast Shutdown feature that initiates shutdown without uninitializing device drivers. However, this can cause Windows 98 to hang instead of shutting down the computer if a buggy driver is active, so Microsoft supplied instructions for disabling the feature. Windows 98 supports write-behind caching for removable disk drives. A utility for converting FAT16 partitions to FAT32 without formatting the partition is also included. Other system tools A number of improvements are made to various other system tools and accessories in Windows 98. Microsoft Backup supports differential backup and SCSI tape devices in Windows 98. Disk Cleanup, a new tool, enables users to clear their disks of unnecessary files. Cleanup locations are extensible through Disk Cleanup handlers. Disk Cleanup can be automated for regular silent cleanups. Scanreg (DOS) and ScanRegW are Registry Checker tools used to back up, restore or optimize the Windows registry. ScanRegW tests the registry's integrity and saves a backup copy each time Windows successfully boots. The maximum number of copies could be customized by the user through "scanreg.ini" file. The restoration of a registry that causes Windows to fail to boot can only be done from DOS mode using ScanReg. System Configuration Utility is a new system utility used to disable programs and services that are not required to run the computer. A Maintenance Wizard is included that schedules and automates ScanDisk, Disk Defragmenter and Disk Cleanup. Windows Script Host, with VBScript and JScript engines is built-in and upgradeable to version 5.6. System File Checker checks installed versions of system files to ensure they were the same version as the one installed with Windows 98 or newer. Corrupt or older versions are replaced by the correct versions. This tool was introduced to resolve the DLL hell issue and was replaced in Windows Me by System File Protection. Windows 98 Setup simplifies installation, reducing the bulk of user input required. The Windows 98 Startup Disk contains generic, real-mode ATAPI and SCSI CD-ROM drivers that can be used instead in the event that the specific driver for a CD-ROM is unavailable. The system could be updated using Windows Update. A utility to automatically notify the user of critical updates was later released. Windows 98 includes an improved version of the Dr. Watson utility that collects and lists comprehensive information such as running tasks, startup programs with their command line switches, system patches, kernel driver, user drivers, DOS drivers and 16-bit modules. With Dr. Watson loaded in the system tray, whenever a software fault occurs (general protection fault, hang, etc.), Dr. Watson will intercept it and indicate what software crashed and its cause. Windows Report Tool takes a snapshot of system configuration and lets users submit a manual problem report along with system information to technicians. It has e-mail confirmation for submitted reports. Accessories Windows 98 includes Microsoft Magnifier, Accessibility Wizard and Microsoft Active Accessibility 1.1 API (upgradeable to MSAA 2.0.) A new HTML Help system with 15 Troubleshooting Wizards was introduced to replace WinHelp. Users can configure the font in Notepad. Microsoft Paint supports GIF transparency. HyperTerminal supports a TCP/IP connection method, which allows it to be used as a Telnet client. Imaging for Windows is updated. System Monitor—used to track the performance of hardware and software—supports output to a log file. Miscellaneous improvements Telephony API (TAPI) 2.1 DCOM version 1.2 Ability to list fonts by similarity determined using PANOSE information. Tools to automate setup, such as Batch 98 and INFInst.exe, support error-checking, gathering information automatically to create an INF file directly from a machine's registry, customizing IE4, shell and desktop settings and adding custom drivers. Several other Resource Kit tools are included on the Windows 98 CD. Windows 98 has new system event sounds for low battery alarm and critical battery alarm. The new startup sound for Windows 98 was composed by Microsoft sound engineer Ken Kato, who considered it to be a "tough act to follow". Windows 98 shipped with Flash Player and Shockwave Player preinstalled. Windows 98 Second Edition Windows 98 Second Edition (often shortened to Windows 98 SE and sometimes to Win98 SE) is an updated version of Windows 98, released on May 5, 1999, nine months before the release of Windows 2000. It includes many bug fixes, improved WDM audio and modem support, improved USB support, the replacement of Internet Explorer 4.0 with Internet Explorer 5.0, Web Folders (WebDAV namespace extension for Windows Explorer), and related shell updates. Also included is basic OHCI-compliant FireWire DV camcorder support (MSDV class driver) and SBP-2 support for mass storage class devices. Wake-On-LAN reenables suspended networked computers due to network activity, and Internet Connection Sharing allows multiple networked client computers to share an Internet connection via a single host computer. Other features in the update include DirectX 6.1 which introduced major improvements to DirectSound and the introduction of DirectMusic, improvements to Asynchronous Transfer Mode support (IP/ATM, PPP/ATM and WinSock 2/ATM support), Windows Media Player 6.1 replacing the older Media Player, Microsoft NetMeeting 3.0, MDAC 2.1 and WMI. A memory overflow issue was resolved which in the older version of Windows 98 would crash most systems if left running for 49.7 days (equal to 232 milliseconds). Windows 98 SE could be obtained as retail upgrade and full version packages, as well as OEM and a Second Edition Updates Disc for existing Windows 98 users. USB audio device class support is present from Windows 98 SE onwards. Windows 98 Second Edition improved WDM support in general for all devices, and it introduced support for WDM for modems (and therefore USB modems and virtual COM ports), Microsoft driver support for both USB printers, and for USB mass-storage device class is not available for Windows 98. Removed features Windows 98 Second Edition did not ship with the WinG API or RealPlayer 4.0, unlike the original release of Windows 98, due to both of these having been superseded by DirectX and Windows Media Player, respectively. Upgradeability Several components of both Windows 98 and Windows 98 Second Edition can be updated to newer versions. These include: Internet Explorer 6 SP1 and Outlook Express 6 SP1 Windows Media Format Runtime and Windows Media Player 9 Series on Windows 98 Second Edition (and Windows Media Player 7.1 on Windows 98 original release.) Windows Media Encoder 7.1 and Windows Media 8 Encoding Utility DirectX 9.0c (the latest compatible runtime is from October 2007.) MSN Messenger 7.0 Significant features from newer Microsoft operating systems can be installed on Windows 98. Chief among them are .NET Framework versions 1.0, 1.1 and 2.0, the Visual C++ 2005 runtime, Windows Installer 2.0, the GDI+ redistributable library, Remote Desktop Connection client 5.2 and the Text Services Framework. Several other components such as MSXML 3.0 SP7, Microsoft Agent 2.0, NetMeeting 3.01, MSAA 2.0, ActiveSync 3.8, WSH 5.6, Microsoft Data Access Components 2.81 SP1, WMI 1.5 and Speech API 4.0. Office XP is the last version of Microsoft Office that is compatible with Windows 98. Although Windows 98 does not fully support Unicode, certain Unicode applications can run if the Microsoft Layer for Unicode is installed. System requirements The two major versions of Windows 98 have minimum requirements needed to be run. Users can bypass processor requirement checks with the undocumented /NM setup switch. This allows installation on computers with processors as old as the Intel 80386. Limitations Windows 98 is only designed to handle up to 1 GB of RAM without changes. Both Windows 98 and Windows 98 Second Edition have problems running on hard drives of capacities larger than 32 GB in systems with certain Phoenix BIOS configurations. A software update fixed this shortcoming. In addition, until Windows XP with Service Pack 1, Windows was unable to handle hard drives that are over 137 GB in size with the default drivers, because of missing 48-bit Logical Block Addressing support. Support lifecycle Support for Windows 98 under Microsoft's consumer product life cycle policy was planned to end on June 30, 2003, however, in December 2002, Microsoft extended the support window to January 16, 2004. This date would then be extended again on January 13, 2004 to a final end of support date of July 11, 2006, citing support volumes in emerging markets as the reason for the extension. Windows 98 retail availability ended as planned on June 30, 2002, and later became completely unavailable from Microsoft (through MSDN or otherwise) in any form due to the terms of Java-related settlements Microsoft made with Sun Microsystems. The Windows Update website continued to be available after Windows 98's end of support date, however, during 2011, Microsoft retired the Windows Update v4 website and removed the updates for Windows 98 and Windows 98SE from its servers. Reception Windows 98 was released to generally favorable reviews, with praise directed to its improved graphical user interface and customizability, ease of use, and the degree to which it addressed complaints that users and critics had with Windows 95. Michael Sweet of Smart Computing characterized it as heavily integrating features of the Internet browser, and found file and folder navigation easier. Ed Bott of PC Computing lauded the bug fixes, easier troubleshooting, and support for hardware advances such as DVD players and USB. However, he also found that the operating system crashed only slightly less frequently, and criticized the high upgrade price and system requirements. He rated it four stars out of five. Sales Windows 98 sold 530,000 licenses in its first four days of availability, overtaking Windows 95's 510,000. It later sold a total of 580,000 and 350,000 licenses in the first and second months of availability, respectively. In the first year of its release, Windows 98 sold a total of 15 million licenses – 2 million more than its predecessor. However, International Data Corporation estimated that of the roughly 89 million shipped computers in the desktop market, the operating system had a market share of 17.2 percent, compared to Windows 95's 57.4 percent. Meanwhile, the two operating systems continued to observe a trend whereby Windows 98 improved in sales performance, whereas Windows 95 dwindled. After a legal dispute and subsequent settlement with Sun Microsystems over the former's Java Virtual Machine, Microsoft ceased distributing the operating system on December 15, 2003, and IDC estimated that a total of 58 million copies were installed worldwide by then. References Further reading External links "Windows 98." – Microsoft (Archive) GUIdebook: Windows 98 Gallery – A website dedicated to preserving and showcasing Graphical User Interfaces 1998 software 1999 software Products and services discontinued in 2006 98 DOS variants IA-32 operating systems

Operating System (OS)

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturing on August 15, 1995, and generally to retail on August 24, 1995. Windows 95 merged Microsoft's formerly separate MS-DOS and Microsoft Windows products, and featured significant improvements over its predecessor, most notably in the graphical user interface (GUI) and in its simplified "plug-and-play" features. There were also major changes made to the core components of the operating system, such as moving from a mainly cooperatively multitasked 16-bit architecture to a 32-bit preemptive multitasking architecture, at least when running only 32-bit protected mode applications. Accompanied by an extensive marketing campaign, Windows 95 introduced numerous functions and features that were featured in later Windows versions, such as the taskbar, notification area, and the "Start" button. Three years after its introduction, Windows 95 was followed by Windows 98. Microsoft ended extended support for Windows 95 on December 31, 2001. Development The initial design and planning of Windows 95 can be traced back to around March 1992, just around the time before the release of Windows 3.1. At this time, Windows for Workgroups 3.11 and Windows NT 3.1 were still in development and Microsoft's plan for the future was focused on Cairo. Cairo would be Microsoft's next-generation operating system based on Windows NT, featuring a new user interface and an object-based file system, but it was not planned to be shipped before 1994. However, Cairo would partially ship in late July 1996 in the form of Windows NT 4.0, but without the object-based file system, which would later evolve into WinFS. Simultaneously with Windows 3.1's release, IBM started shipping OS/2 2.0. Microsoft realized they required an updated version of Windows that could support 32-bit applications and preemptive multitasking, but could still run on low-end hardware (Windows NT did not). So the development of Windows "Chicago" was started and, as it was planned for a late 1993 release, became known as Windows 93 which was also known as Windows 4.0. Initially, the decision was not to include a new user interface, as this was planned for Cairo, and only focused on making installation, configuration, and networking easier. Windows 93 would ship together with MS-DOS 7.0, offering a more integrated experience to the user and making it pointless for the user to buy a DOS clone; this anti-competitive practice was denounced in Caldera v. Microsoft. MS-DOS 7.0 was in development at that time under the code name "Jaguar" and could optionally run on top of a Windows 3.1-based 32-bit protected-mode kernel called "Cougar" to better compete with DR-DOS. The first version of Chicago's feature specification was finished on September 30, 1992. Cougar was to become Chicago's kernel. Beta Before Windows 95's official release, users in the United States and United Kingdom had an opportunity to participate in the Windows 95 Preview Program. For US$19.95/£19.95, users would receive several 3.5-inch floppy disks that would be used to install Windows 95 either as an upgrade from Windows 3.1x or as a fresh installation. Participants were also given a free preview of The Microsoft Network (MSN), the online service that Microsoft launched with Windows 95. During the preview period, Microsoft established various electronic distribution points for promotional and technical documentation on Chicago, including a detailed document for media reviewers describing the new system highlights. The preview versions expired in November 1995, after which the user would have to purchase their copy of the final version of Windows 95. Architecture Windows 95 was designed to be maximally compatible with existing MS-DOS and 16-bit Windows programs and device drivers while offering a more stable and better performing system. The Windows 95 architecture is an evolution of Windows for Workgroups' 386 enhanced mode. The lowest level of the operating system consists of a large number of virtual device drivers (VxDs) running in 32-bit protected mode and one or more virtual DOS machines running in virtual 8086 mode. The virtual device drivers are responsible for handling physical devices (such as video and network cards), emulating virtual devices used by the virtual machines or providing various system services. The three most important virtual device drivers are: Virtual Machine Manager (VMM32.VXD)Responsible for memory management, event handling, interrupt handling, loading and initializing virtual device drivers, creating new virtual machines and thread scheduling. Configuration Manager (CONFIGMG)Responsible for implementing Plug and Play functionality; monitoring hardware configuration changes; detecting devices using bus enumerators; and allocating I/O ports, IRQs, DMA channels and memory in a conflict-free fashion. Installable File System Manager (Input/Output Subsystem)Coordinates access to supported file systems. Windows 95 initially shipped with support for FAT12, FAT16, the VFAT extension, ISO 9660 (CDFS), Joliet and network redirectors, with later releases supporting FAT32. Access requests to physical media are sent to Input/Output Supervisor, a component responsible for scheduling the requests. Each physical media has its device driver: access to the disk is performed by a port driver, while access to a SCSI device is handled by a miniport driver working atop the SCSI layer. Port and Miniport drivers perform I/O operations in 32-bit protected mode, bypassing MS-DOS and BIOS, significantly improving performance. In case there is no native Windows driver for a certain storage device, or if a device is forced to run in compatibility mode, the Real Mode Mapper can access it through MS-DOS. 32-bit Windows programs are assigned their memory segments, which can be adjusted to any desired size. Memory areas outside the segment cannot be accessed by a program. If a program crashes, nothing else is harmed. Before this, programs used fixed non-exclusive 64 KB segments. While the 64 KB size was a serious handicap in DOS and Windows 3.x, lack of guarantee of exclusiveness was the cause of stability issues because programs sometimes overwrote each other's segments. A crashing Windows 3.x program could knock out surrounding processes. The Win32 API is implemented by three modules, each consisting of a 16-bit and a 32-bit component: KernelProvides high level access to memory and process management, and access to the file system. Consists of KRNL386.EXE, KERNEL32.DLL, and VWIN32.VXD. UserResponsible for managing and drawing the various user interface components, such as windows, menus and buttons. Consists of USER.EXE and USER32.DLL. Graphics Device Interface (GDI) Responsible for drawing graphics in a device-independent way. Consists of GDI.EXE and GDI32.DLL. Dependence on MS-DOS To end-users, MS-DOS appears as an underlying component of Windows 95. For example, it is possible to prevent the loading of the graphical user interface and boot the system into a real-mode MS-DOS environment. This was done by inserting command.com in the autoexec.bat file or changing the BootGUI variable in the MSDOS.SYS file to 0. This sparked debate amongst users and professionals regarding the extent to which Windows 95 is an operating system or merely a graphical shell running on top of MS-DOS. When the graphical user interface is started, the virtual machine manager takes over the filesystem-related and disk-related functionality. MS-DOS itself is demoted to a compatibility layer for 16-bit device drivers. This contrasts with earlier versions of Windows which rely on MS-DOS to perform file and disk access (Windows for Workgroups 3.11 could also largely bypass MS-DOS when 32-bit file access and 32-bit disk access were enabled). Keeping MS-DOS in memory allows Windows 95 to use DOS device drivers when suitable Windows drivers are unavailable. Windows 95 is capable of using all 16-bit Windows 3. x drivers. Unlike Windows 3.1x, DOS programs running in Windows 95 do not need DOS drivers for the mouse, CD-ROM and sound card; Windows drivers are used instead. HIMEM.SYS is still required to boot Windows 95. EMM386 and other memory managers, however, are only used by DOS programs. In addition, CONFIG.SYS and AUTOEXEC.BAT settings (aside from HIMEM.SYS) do not affect Windows programs. DOS games, which could not be executed on Windows 3. x, can run inside Windows 95 (games tended to lock up Windows 3. x or cause other problems). As with Windows 3. x, DOS programs that use EGA or VGA graphics modes run in windowed mode (CGA and text mode programs can continue to run). On startup, the MS-DOS component in Windows 95 responds to a pressed key by temporarily pausing the default boot process and presenting the DOS boot options menu, allowing the user to continue starting Windows normally, start Windows in safe mode or exit to the DOS prompt. As in previous versions of MS-DOS, there is no 32-bit support and DOS drivers must be loaded for mice and other hardware. As a consequence of DOS compatibility, Windows 95 has to keep internal DOS data structures synchronized with those of Windows 95. When starting a program, even a native 32-bit Windows program, MS-DOS momentarily executes to create a data structure known as the Program Segment Prefix. It is even possible for MS-DOS to run out of conventional memory while doing so, preventing the program from launching. Windows 3.x allocated fixed segments in conventional memory first. Since the segments were allocated as fixed, Windows could not move them, which would prevent any more programs from launching. Microsoft partially removed support for File Control Blocks (an API hold-over of DOS 1. x and CP/M) in Windows 95 OSR2 (OEM Service Release 2). FCB functions can read FAT32 volumes, but not write to them. User interface Windows 95 introduced a redesigned shell based around a desktop metaphor; File shortcuts (also known as shell links) were introduced and the desktop was re-purposed to hold shortcuts to applications, files and folders, reminiscent of Mac OS. In Windows 3.1 the desktop was used to display icons of running applications. In Windows 95, the currently running applications were displayed as buttons on a taskbar across the bottom of the screen. The taskbar also contained a notification area used to display icons for background applications, a volume control and the current time. The Start menu, invoked by clicking the "Start" button on the taskbar or by pressing the Windows key, was introduced as an additional means of launching applications or opening documents. While maintaining the program groups used by its predecessor Program Manager, it also displayed applications within cascading sub-menus. The previous File Manager program was replaced by Windows Explorer and the Explorer-based Control Panel and several other special folders were added such as My Computer, Dial-Up Networking, Recycle Bin, Network Neighborhood, My Documents, Recent documents, Fonts, Printers, and My Briefcase among others. AutoRun was introduced for CD drives. The user interface looked dramatically different from prior versions of Windows, but its design language did not have a special name like Metro, Aqua or Material Design. Internally it was called "the new shell" and later simply "the shell". The subproject within Microsoft to develop the new shell was internally known as "Stimpy". In 1994, Microsoft designers Mark Malamud and Erik Gavriluk approached Brian Eno to compose music for the Windows 95 project. The result was the six-second start-up music-sound of the Windows 95 operating system, The Microsoft Sound and it was first released as a startup sound in May 1995 on Windows 95 May Test Release build 468. When released for Windows 95 and Windows NT 4.0, Internet Explorer 4 came with an optional Windows Desktop Update, which modified the shell to provide several additional updates to Windows Explorer, including a Quick Launch toolbar, and new features integrated with Internet Explorer, such as Active Desktop (which allowed Internet content to be displayed directly on the desktop). Some of the user interface elements introduced in Windows 95, such as the desktop, taskbar, Start menu and Windows Explorer file manager, remained fundamentally unchanged on future versions of Windows. Technical improvements Windows 95 included support for 255-character mixed-case long filenames and preemptively multitasked protected-mode 32-bit applications. 16-bit processes were still co-operatively multitasked. Plug and Play Windows 95 tried to automate device detection and configuration as much as possible, but could still fall back to manual settings if necessary. During the initial install process of Windows 95, it would attempt to automatically detect all devices installed in the system. Windows 95 also introduced the Device Manager to indicate which devices were working optimally with correct drivers and configuration and to allow the user to override automatic Plug and Play-based driver installation with manual options or give a choice of several semi-automatic configurations to try to free up resources for devices that still needed manual configuration. Long file names 32-bit File Access is necessary for the long file names feature introduced with Windows 95 through the use of the VFAT file system extension. It is available to both Windows programs and MS-DOS programs started from Windows (they have to be adapted slightly, since accessing long file names requires using larger pathname buffers and hence different system calls). Competing DOS-compatible operating systems released before Windows 95 cannot see these names. Using older versions of DOS utilities to manipulate files means that the long names are not visible and are lost if files are moved or renamed and by the copy (but not the original) if the file is copied. During a Windows 95 automatic upgrade of an older Windows 3.1 system, DOS and third-party disk utilities which can destroy long file names are identified and made unavailable. When Windows 95 is started in DOS mode, e.g. for running DOS programs, low-level access to disks is locked out. In case the need arises to depend on disk utilities that do not recognize long file names, such as the MS-DOS 6. x's defrag utility, a program called LFNBACK for backup and restoration of long file names is provided on the CD-ROM, specifically in its \ADMIN\APPTOOLS\LFNBACK directory. 32-bit Windows 95 followed Windows for Workgroups 3.11 with its lack of support for older, 16-bit x86 processors, thus requiring an Intel 80386 (or compatible). While the OS kernel is 32-bit, much code (especially for the user interface) remained 16-bit for performance reasons as well as development time constraints. This had a rather detrimental effect on system stability and led to frequent application crashes. The introduction of 32-bit file access in Windows for Workgroups 3.11 meant that 16-bit real mode MS-DOS is not used for managing the files while Windows is running, and the earlier introduction of the 32-bit disk access means that the PC BIOS is often no longer used for managing hard disks. DOS can be used for running old-style drivers for compatibility, but Microsoft discourages using them, as this prevents proper multitasking and impairs system stability. Control Panel allows a user to see which MS-DOS components are used by the system; optimal performance is achieved when they are bypassed. The Windows kernel uses MS-DOS style real-mode drivers in Safe Mode, which exists to allow a user to fix problems relating to loading native, protected-mode drivers. Core improvements in OEM Service Releases OEM Service Releases of Windows 95 introduced support in Windows for several core new technologies which were not included in the original release of Windows 95. These include the Internet Explorer web browser, DriveSpace compression, DirectX, FAT32 file system support, UltraDMA mode for disk drives, Universal Serial Bus, IEEE 1394 (FireWire), and Accelerated Graphics Port. Accessibility features Windows 95 introduced computer accessibility features like Sticky keys, FilterKeys, ToggleKeys, Mouse keys. Microsoft Active Accessibility API was introduced as an add-on for Windows 95. System requirements Official system requirements were an Intel 386DX CPU of any speed, 4 MB of system RAM and 50–55 MB of hard disk space depending on features selected. These minimal claims were made in order to maximize the available market of Windows 3.1 migrations. This configuration would rely heavily on virtual memory and was only optimal for productive use on single-tasking dedicated workstations. It was possible to run Windows 95 on a 386 SX, but this led to even less acceptable performance due to its 16-bit external data bus. To achieve optimal performance, Microsoft recommended an i486 or compatible CPU with at least 8 MB of RAM. Windows 95 may fail to boot on computers with a processor faster than 2.1 GHz and more than approximately 480 MB of memory. In such a case, reducing the file cache size or the size of video memory can help. The theoretical maximum according to Microsoft is 2 GB. Most copies of Windows 95 were on CD-ROM, but a -inch floppy version was also available for older machines. The retail floppy disk version of Windows 95 came on 13 DMF formatted floppy disks, while OSR 2.1 doubled the floppy count to 26. Both versions exclude additional software that the CD-ROM version might have featured. Microsoft Plus! for Windows 95 was also available on floppy disks. Upgradeability Windows 95 was superseded by Windows 98 and could still be directly upgraded by either Windows 2000 Professional or Windows Me. Office 2000 is the last version of Microsoft Office to be compatible with Windows 95. Similarly, Windows Media Player 6.4, released in April 1999, and DirectX 8.0a, released in February 2001, are the last versions of Windows Media Player and DirectX available for Windows 95, respectively. Internet Explorer Windows 95 originally shipped without Internet Explorer, and the default network installation did not install TCP/IP, the network protocol used on the Internet. At the release date of Windows 95, Internet Explorer 1.0 was available, but only in the Plus! add-on pack for Windows 95, which was a separate product. The Plus! The pack did not reach as many retail consumers as the operating system itself (it was mainly advertised for its non-Internet-related add-ons such as themes and better disk compression) but was usually included in pre-installed (OEM) sales, and at the time of Windows 95's release, the web was being browsed mainly with a variety of early web browsers such as NCSA Mosaic and Netscape Navigator (promoted by-products such as IBox). Windows 95 OEM Service Release 1 was the first release of Windows to include Internet Explorer (version 2.0) with the OS. While there was no uninstaller, it could be deleted easily if desired. OEM Service Release 2 included Internet Explorer 3. The installation of Internet Explorer 4 on Windows 95 (or the OSR2.5 version preinstalled on a computer) gave Windows 95 Active Desktop and browser integration into Windows Explorer, known as the Windows Desktop Update. The CD version of the last release of Windows 95, OEM Service Release 2.5 (version 4.00.950C), includes Internet Explorer 4, and installs it after Windows 95's initial setup and first boot are complete. While only the 4.x series of the browser contained the option to install the Windows Desktop Update features, the subsequent 5.x version had the option hidden. Editing the installer's configuration file located in a temporary folder would make the feature available in the installer. Alternatively, the user could install IE 4 with the desktop update before installing a newer version of Internet Explorer. The last version of Internet Explorer supported on Windows 95 is Internet Explorer 5.5 with SP2, which was released on July 23, 2001. Windows 95 shipped with Microsoft's dial-up online service called The Microsoft Network (MSN). Release and promotion The Windows 95 release included a commercial featuring The Rolling Stones' 1981 single "Start Me Up" (a reference to the Start button). It was widely reported that Microsoft paid the Rolling Stones between US$8 and US$14 million for the use of the song in the Windows 95 advertising campaign. However, Microsoft said that this was just a rumour spread by the band to increase their market value, and the company paid US$3 million. A 30-minute promotional video, labeled a "cyber sitcom," featuring Jennifer Aniston and Matthew Perry, was also released to showcase the features of Windows 95. Microsoft's US$200 million advertising campaign featured stories of people waiting in line outside stores to get a copy. In the UK, the largest computer chain PC World received a large quantity of point-of-sale material; many branches opened at midnight to sell the first copies of the product. Copies of The Times were available for free, and Microsoft paid for 1.5 million issues (twice the daily circulation at the time). In the United States, the Empire State Building in New York City was lit to match the colors of the Windows logo. In Canada, a banner was hung down the side of the CN Tower in Toronto. The release included a number of "Fun Stuff" items on the CD, including music videos of Edie Brickell's "Good Times" and Weezer's "Buddy Holly," a trailer for the 1995 film Rob Roy and the computer game Hover! Sales were strong, with one million copies shipped worldwide in just four days. According to International Data Corporation, by the end of 1998, Windows 95 was the most used desktop OS with 57.4% of the marketshare, with its successor Windows 98 coming in second at 17.2%. Windows 95 also still sold more non-OEM copies to large customers in the month of May 1999, which analysts attributed to large companies opting to wait for the release of Windows 2000. Editions Several Windows 95 editions have been released. Only the original release was sold as a shrink-wrapped product; later editions were provided only to computer OEMs for installation on new PCs. For this reason, these editions are known as OEM Service Releases (OSR). Together with the introduction of Windows 95, Microsoft released the Microsoft Plus! for Windows 95 pack, which contained several optional components for high-end multimedia PCs, including Internet Explorer, DriveSpace and additional themes. The first service pack was made available half a year after the original release and fixed several small bugs. The second service pack mainly introduced support for new hardware, most notably support for hard drives larger than 2 GB in the form of the FAT32 file system. This release was never made available to end-users directly and was only sold through OEMs with the purchase of a new PC. A full third service pack was never released, but two smaller updates to the second were released in the form of a USB Supplement (OSR 2.1) and the Windows Desktop Update (OSR 2.5). Both were available as stand-alone updates and as updated disc images shipped by OEMs. OSR 2.5 was notable for featuring several changes to the Windows Explorer, integrating it with Internet Explorer 4.0—this version of Internet Explorer looks very similar to the one featured in Windows 98. Legacy On December 31, 2001, Microsoft ended its support for Windows 95, making it an "obsolete" product per the Microsoft Lifecycle Policy. Many features have since become key components of the Microsoft Windows series, such as the Start menu and the taskbar, originated in Windows 95. Neil MacDonald, a Gartner analyst, said that Windows 95 "was a quantum leap in difference in technological capability and stability." Ina Fried of CNET said that "by the time Windows 95 was finally ushered off the market in 2001, it had become a fixture on computer desktops around the world." Even though support for Windows 95 has ended, the software has occasionally remained in use on legacy systems for various purposes. In addition, some video game enthusiasts choose to use Windows 95 for their legacy system to play old DOS games, although some other versions of Windows such as Windows 98 can also be used for this purpose. Windows 95 was implemented into a web-based DOSBox emulator around early 2016. In March 2016, Fine Brothers Entertainment uploaded a reaction video on YouTube titled Teens React to Windows 95, wherein the teens complained about lack of Wi-Fi and having to use dial-up to access the Internet. The video received more than 14 million views and prompted stories in more than a dozen publications. See also Windows 9x References Further reading Microsoft: Third-party: 1995 software Products and services discontinued in 2001 DOS variants 95 IA-32 operating systems Products introduced in 1995

Operating System (OS)

General Comprehensive Operating System General Comprehensive Operating System (GCOS, ; originally GECOS, General Electric Comprehensive Operating Supervisor) is a family of operating systems oriented toward the 36-bit GE/Honeywell mainframe computers. The original version of GCOS was developed by General Electric from 1962. The operating system is still used today in its most recent versions (GCOS 7 and GCOS 8) on servers and mainframes produced by Groupe Bull, primarily through emulation, to provide continuity with legacy mainframe environments. GCOS 7 and GCOS 8 are separate branches of the operating system and continue to be developed alongside each other. History GECOS The GECOS operating system was developed by General Electric for the 36-bit GE 600 Series in 1962-1964 and renamed GECOS II in November 1965. It bore a close resemblance architecturally to IBSYS on the IBM 7094 and less to DOS/360 on the System/360. However, the GE 600 Series four processor architecture was very different from the IBM System/360 and GECOS was more ambitious than DOS/360. GECOS-II supported both time-sharing (TSS) and batch processing, with dynamic allocation of memory (IBM had fixed partitions, at that time), making it a true second-generation operating system. Honeywell GCOS 3 After Honeywell acquired GE's computer division, GECOS-III was renamed GCOS 3, and the hardware line was renamed to the H-6000 adding the EIS (enhanced instruction set, character oriented instead of word oriented). GCOS 64 The name "GCOS" was extended to the operating systems for all Honeywell-marketed product lines. GCOS-64, a completely different 32-bit operating system for the Level 64 series, similar to a parallel development called Multics, was designed by Honeywell and Honeywell Bull developers in France and Boston. GCOS 61/62 GCOS-62, the operating system for another 32-bit low-end line of machines, the Level 62 series, was designed in Italy. GCOS-61 was the operating system for a new version of a small system made in France (Model 58, later Level 61/58), and the operating system for a new 16-bit minicomputer line from Massachusetts (Billerica), the Level 6, got the name GCOS 6. GCOS 7 and GCOS 8 Another renaming of the hardware product lines occurred in 1979, with the Level 6 becoming the DPS 6, the Level 62 becoming the DPS 4, the Level 64 becoming DPS 7, and Level 66 becoming DPS 8. Operating Systems retained the GCOS brand-name, with GCOS 6, GCOS 4, GCOS 7, and GCOS 8 being introduced. GCOS 8 was an extensive rewrite of GCOS 3, with changes made to support true virtual memory management and demand paging (these changes also required new hardware). GCOS 3 was supported in maintenance for several years after this announcement and renaming. Legacy DPS 6 and DPS 4 (ex-Level 62) were superseded by Motorola 68000 and later on PowerPC minicomputers running Unix and the product lines were discontinued, though GCOS 6 ran in an emulator on top of AIX. The DPS 7 line, along with GCOS 7, continued to evolve into the DPS 7000 hardware base. In the late 1980s Honeywell sold its computer business to a joint venture that initially included NEC and Bull, with Honeywell still holding a stake for a time. Over a couple of years, Bull took over the company. NEC supplied several generations of mainframe hardware at the high end, which would run both GCOS 8 and their own ACOS-4 Operating System. Bull used the nomenclature DPS-9000 for its entire GCOS 8-based mainframe line, which included models designed by both Bull and NEC. By the late 1990s and early 2000s, Bull's desire was to center its development on a single hardware base, running commodity Intel chips but with Bull value-adds. This platform, called Novascale and based on Itanium 2 processors, runs both Windows and Linux natively. However, Instruction Set Simulators for both the DPS 7000 and DPS 9000 allowed GCOS 7 and GCOS 8 to run on this platform. GCOS 7 has also been ported to Xeon-based hardware. Bull continues to invest development money in support of both GCOS 7 and GCOS 8, and still has customers in countries around the world. Support for GCOS 7 and GCOS 8 from Bull is planned through at least 2025 including regular hardware and software upgrades. A trace of GCOS influence remains today in modern UNIX systems. Some early Unix systems at Bell Labs used GCOS machines for print spooling and various other services. The field added to "/etc/passwd" to carry GCOS ID information was called the "GECOS field" and survives today as the "pw_gecos" member used for the user's full name and other human-ID information. Applications GCOS 3 (and later GCOS 7 and GCOS 8) featured a good Codasyl "relational" database called Integrated Data Store (IDS) that was the model for the more successful IDMS. Several transaction processing monitors were designed for GCOS 3 and GCOS 8. An early attempt at Transaction processing (TP) for GCOS 3, the Transaction Processing Executive, assumed that, as in Unix, a new process should be started to handle each transaction, and enjoyed only very limited success. Another TP system, the Transaction Driven System (TDS), was soon developed for GCOS 3, using a single process (potentially with multiple threads) to service all transactions. TDS was essentially a Honeywell development. It was later replaced by the backward-compatible Transaction Processing 8 (TP8) on GCOS 8, which profited from the overhaul in GCOS system architecture that came with GCOS 8 to make full use of virtual memory concepts. TP8 used multiple static processes in a way similar to UNIX daemons to handle incoming transactions in a multiplexed way. TDS and its TP8 successor were commercially successful, and TDS predated IBM CICS, which had a very similar architecture. A similar product also called TDS was developed for GCOS-7, but the internal architecture was completely different. System architecture and concepts GCOS is a multithreading, multiprogramming operating system originally oriented towards batch processing, although later versions incorporated enhancements for timesharing and online transaction processing environments. Systems running GCOS today use it mainly for batch and OLTP, or as a backend enterprise server. GCOS has a basic architecture similar to that of operating systems for the IBM 360 and earlier IBM 7090 Series, and subsequent operating systems with which it competed. It was also heavily influenced by projects such as MEDINET, Multics, and WWMCCS, and has inherited a strong security structure in consequence. Hardware and software features combine to render the operating system unusually secure for an operating system of its generation and class. Multics influenced the design of the hardware, with gate-oriented secure transfer-of-control instructions and a hardware-enforced system of security levels very similar to that of the famous Multics rings. Operational environments such as WWMCCS drove development of special security features to allow secure hosting of classified information and compartmentalization. For a time separate versions of the GCOS system with special security features turned on were maintained specifically for government customers. Early versions of GCOS and the hardware it ran on did not support paged virtual memory but did support a single memory segment per process. This made it inferior for time-sharing, especially compared with hardware designed to support Multics and the contemporaneous DEC PDP-10 hardware. GCOS is a process-oriented OS, in which each process hosts one or more execution threads and executes in its own virtual memory space. Virtual memory is divided into segments of arbitrary size reminiscent of Multics segments, and a second level of address translation converts pure virtual addresses to pageable addresses, which are then converted to real addresses in main memory or backing store. Segments and pages and other constructs include hardware-enforced security parameters. The top-level virtual memory architecture also simplifies sharing of code and data in a secure fashion, again in a way reminiscent of Multics. Each GCOS version was designed for specific hardware. The most recent machines capable of running the OS do so through emulation of that hardware. The hardware originally had much in common with Multics hardware, so much so that some mainframe equipment could be switched from "GCOS mode" to "Multics mode" with the turn of a dial. Much of the peripheral equipment used with GCOS could also be used with Multics, although front-end network processors were very different between the two systems. Program languages available for GCOS included GCOS Algol, Algol-68, COBOL, SNOBOL, JOVIAL, APL, FORTRAN 68, CORAL 66, FORTRAN 77, and B. GCOS8 Storage Units Modern terminology for units of storage applies across various operating systems and computer vendors, and is part of everyday conversation. Terms like megabyte and gigabyte mean much the same to everyone, and terms like mebibyte and gibibyte have been formally standardised. However, the GCOS8 system pre-dates this mono-culture with some colourful units of its own, as follows: Note that in this system a byte contains 9 bits with values ranging from (000)8 to (777)8 or 0–511, unlike the usual 8-bit-bytes with values ranging from (000)8 to (377)8 or 0-255. This is due to the 36-bit CPU architecture. Permanent file sizes were specified in Llinks (1280 bytes). Temporary file sizes were specified in Links (15,360 bytes). Since the early 1970s, all GCOS 3 and GCOS 8 disk drives used Logical Block Addressing (LBA). Notes See also Timeline of operating systems Mainframe computer Advanced Comprehensive Operating System Gecos field, typically used to record general information about user accounts on Unix-like operating systems References External links Novascale GCOS – The Groupe Bull GCOS product page. AN INTRODUCTION TO GCOS BATCH PROCESSING (for Timesharing Users), Access Date September 6, 2018 1962 software Computer-related introductions in 1962 General Electric mainframe computers Honeywell mainframe computers Multics-like Proprietary operating systems Mainframe computer software

Operating System (OS)

MS-DOS 7 MS-DOS 7 is a real mode operating system which has never been released separately by its creator Microsoft, but included in the Windows 9x family of operating systems. Windows 95 RTM reports to be MS-DOS 7.0, while Windows 95 OSR2, Windows 95 OSR2.5, Windows 98 and Windows 98SE report as 7.1. Overview A major difference between earlier versions of MS-DOS is the usage of the MSDOS.SYS file. In version 7 this is not a binary file, but a pure setting file. The older boot style, where Windows is not automatically started and the system boots into a DOS command shell, could keep on using that same style by setting BootGUI=0 in the MSDOS.SYS-file. Otherwise, Windows from Windows 95 onward will automatically start up on boot. However this was in reality only an automatic call for the command WIN.COM, the Windows starting program. Windows 95 and 98 are both dependent on MS-DOS to boot the 32 bits kernel and run legacy 16 bits MS-DOS device drivers, although MS-DOS 7 possibly is more "hidden" than earlier versions of MS-DOS. This is also true for Windows Millennium Edition, but "ME" prevents users from booting MS-DOS without booting the 32-bit Windows kernel. Also the paths for (a plausible but actually not necessary) Windows directory and Boot directory are to be set in this new version of the MSDOS.SYS file. Whilst IO.SYS (although binary different) remained as the initial executive startup file which BIOS booting routines fire up, if located correctly. Also the COMMAND.COM file implements the command prompt. The typical DOS setting files CONFIG.SYS and AUTOEXEC.BAT essentially retained their functions from earlier versions of MS-DOS (although memory allocation was no longer needed). Although only included in Windows releases (the last official standalone release of MS-DOS ever was version 6.22), MS-DOS 7 can fairly easily be extracted from Windows 95/98, and be used alone on other computers, just as the earlier versions. Actually MS-DOS 7/7.1 works fine on many modern (as of 2016) motherboards (at least with PS2-keyboards), in sharp contrast to Windows 95/98. It has to be installed on a fairly small partition, located at "the top" of the hard drive and formatted as FAT. Another difference is that MS-DOS 7/7.1 requires a 80386 or higher processor, it fails to boot on 80286-class or lower x86 hardware. MS-DOS 7.1 added FAT32 support, while MS-DOS 7.0 and earlier versions of MS-DOS only supported FAT12 and FAT16. MS-DOS must be installed, prior to any Windows installation, through the SYS command (executing the SYS.COM file), preferably from a folder on a Ramdrive created by a bootable disc. Correct versions of IO.SYS (especially) must exist in the same folder as SYS.COM together with DRVSPACE.BIN, MSDOS.SYS, MSDOS.--- as well as COMMAND.COM, AUTOEXEC.BAT and CONFIG.SYS. All other files can be copied thereafter. (In Windows 95/98 they are found in either the root folder or in the C:\WINDOWS\COMMAND folder) See also PC DOS 7 List of DOS commands List of DOS system files Timeline of DOS operating systems References Notes A.There was a "MS-DOS 7.1" made by China DOS Union, which is the same as the Windows 9x version, but bundled as a standalone OS with a multitude of utilities. Source: WinWorld. Disk operating systems Microsoft operating systems Proprietary operating systems 1995 software

Operating System (OS)

IBM PC DOS IBM PC DOS, an acronym for IBM Personal Computer Disk Operating System, is a discontinued disk operating system for IBM PC compatibles, manufactured and sold by IBM from the early 1980s into the 2000s. Developed by Microsoft, it was also sold by that company as MS-DOS. Versions of both operating systems remained identical or almost identical until 1993, when IBM began selling PC DOS 6.1 with new features. History The IBM task force assembled to develop the IBM PC decided that critical components of the machine, including the operating system, would come from outside vendors. This radical break from company tradition of in-house development was one of the key decisions that made the IBM PC an industry standard. Microsoft, founded five years earlier by Bill Gates, was eventually selected for the operating system. IBM wanted Microsoft to retain ownership of whatever software it developed, and wanted nothing to do with helping Microsoft, other than making suggestions from afar. According to task force member Jack Sams: The reasons were internal. We had a terrible problem being sued by people claiming we had stolen their stuff. It could be horribly expensive for us to have our programmers look at code that belonged to someone else because they would then come back and say we stole it and made all this money. We had lost a series of suits on this, and so we didn't want to have a product which was clearly someone else's product worked on by IBM people. We went to Microsoft on the proposition that we wanted this to be their product. IBM first contacted Microsoft to look the company over in July 1980. Negotiations continued over the months that followed, and the paperwork was officially signed in early November. Although IBM expected that most customers would use PC DOS, the IBM PC also supported CP/M-86, which became available six months after PC DOS, and UCSD p-System operating systems. IBM's expectation proved correct: one survey found that 96.3% of PCs were ordered with the PC DOS compared to 3.4% with the CP/M-86. Over the history of IBM PC DOS, various versions were developed by IBM and Microsoft. By the time PC DOS 3.0 was completed, IBM had a team of developers covering the full OS. At that point in time, either IBM or Microsoft completely developed versions of IBM PC DOS going forward. By 1985 the joint development agreement (JDA) between IBM and Microsoft for the development of PC DOS had each company giving the other company a completely developed version. Most of the time branded versions were identical, but there were some cases in which each of the companies made minor modifications to their version of DOS. In the fall of 1984, IBM gave all the source code and documentation of the internally developed IBM TopView for DOS to Microsoft so that Microsoft could more fully understand how to develop an object-oriented operating environment, overlapping windows (for its development of Windows 2.0) and multitasking. Versions PC DOS 1.x Microsoft first licensed, then purchased 86-DOS from Seattle Computer Products (SCP), which was modified for the IBM PC by Microsoft employee Bob O'Rear with assistance from SCP (later Microsoft) employee Tim Paterson. O'Rear got 86-DOS to run on the prototype PC in February 1981. 86-DOS had to be converted from 8-inch to 5.25-inch floppy disks and integrated with the BIOS, which Microsoft was helping IBM to write. IBM had more people writing requirements for the computer than Microsoft had writing code. O'Rear often felt overwhelmed by the number of people he had to deal with at the ESD (Entry Systems Division) facility in Boca Raton, Florida. Perhaps the first public mention of the operating system was in July 1981, when Byte discussed rumors of a forthcoming personal computer with "a CP/M-like DOS ... to be called, simply, 'IBM Personal Computer DOS. 86-DOS was rebranded IBM PC DOS 1.0 for its August 1981 release with the IBM PC. The initial version of DOS was largely based on CP/M-80 1.x and most of its architecture, function calls and file-naming conventions were copied directly from the older OS. The most significant difference was the fact that it introduced a different file system, FAT12. Unlike all later DOS versions, the and commands were separate executables rather than part of . Single-sided 160 kilobyte (KB) 5.25-inch floppies were the only disk format supported. In late 1981 Paterson, now at Microsoft, began writing PC DOS 1.10. It debuted in May 1982 along with the Revision B IBM PC. Support for the new double-sided drives was added, allowing 320 KB per disk. A number of bugs were fixed, and error messages and prompts were made less cryptic. The utility was now able to load files greater than 64 KB in size. PC DOS 2.x Later, a group of Microsoft programmers (primarily Paul Allen, Mark Zbikowski and Aaron Reynolds) began work on PC DOS 2.0. Completely rewritten, DOS 2.0 added subdirectories and hard disk support for the new IBM XT, which debuted in March 1983. A new 9-sector format bumped the capacity of floppy disks to 360 KB. The Unix-inspired kernel featured file handles in place of the CP/M-derivative file control blocks and loadable device drivers could now be used for adding hardware beyond that which the IBM PC BIOS supported. BASIC and most of the utilities provided with DOS were substantially upgraded as well. A major undertaking that took almost 10 months of work, DOS 2.0 was more than twice as big as DOS 1.x, occupying around 28 KB of RAM compared to the 12 KB of its predecessor. It would form the basis for all Microsoft consumer-oriented OSes until 2001, when Windows XP (based on Windows NT) was released. In October 1983 (officially 1 November 1983) DOS 2.1 debuted. It fixed some bugs and added support for half-height floppy drives and the new IBM PCjr. In 1983, Compaq released the Compaq Portable, the first 100% IBM PC compatible and licensed their own OEM version of DOS 1.10 (quickly replaced by DOS 2.00) from Microsoft. Other PC compatibles followed suit, most of which included hardware-specific DOS features, although some were generic. PC DOS 3.x In August 1984, IBM introduced the Intel 80286-derived IBM PC/AT, its next-generation machine. Along with this was DOS 3.00. Despite jumping a whole version number, it again proved little more than an incremental upgrade, adding nothing more substantial than support for the AT's new 1.2 megabyte (MB) floppy disks. Planned networking capabilities in DOS 3.00 were judged too buggy to be usable and Microsoft disabled them prior to the OS's release. In any case, IBM's original plans for the AT had been to equip it with a proper next-generation OS that would use its extended features, but this never materialized. PC DOS 3.1 (released March 1985) fixed the bugs in DOS 3.00 and supported IBM's Network Adapter card on the IBM PC Network. PC DOS 3.2 added support for -inch double-density 720 KB floppy disk drives, supporting the IBM PC Convertible, IBM's first computer to use -inch floppy disks, released April 1986, and later the IBM Personal System/2 in 1987. In June 1985, IBM and Microsoft signed a long-term Joint Development Agreement to share specified DOS code and create a new operating system from scratch, known at the time as Advanced DOS. On 2 April 1987 OS/2 was announced as the first product produced under the agreement. At the same time, IBM released its next generation of personal computers, the IBM Personal System/2 (PS/2). PC DOS 3.3, released with the PS/2 line, added support for high density -inch 1.44 MB floppy disk drives, which IBM introduced in its 80286-based and higher PS/2 models. The upgrade from DOS 3.2 to 3.3 was completely written by IBM, with no development effort on the part of Microsoft, who were working on "Advanced DOS 1.0". DOS 3.30 was the last version designed with the IBM XT and floppy-only systems in mind; it became one of the most popular versions and many users preferred it to its buggy successor. PC DOS 4.x PC DOS 4.0 (internally known as DOS 3.4 originally), shipped July 1988. DOS 4.0 had some compatibility issues with low-level disk utilities due to some internal data structure changes. DOS 4.0 used more memory than DOS 3.30 and it also had a few glitches. Newly added EMS drivers were only compatible with IBM's EMS boards and not the more common Intel and AST ones. DOS 4.0 is also notable for including the first version of the DOS Shell, a full-screen utility designed to make the command-line OS more user-friendly. Microsoft took back control of development and released a bug-fixed DOS 4.01. PC DOS 5 DOS 5 debuted in June 1991. DOS 5 supported the use of the High Memory Area (HMA) and Upper Memory Blocks (UMBs) on 80286 and later systems to reduce its conventional memory usage. Also all DOS commands now supported the option to display command syntax. Aside from IBM's PC DOS, MS-DOS was the only other version available as OEM editions vanished since by this time PCs were 100% compatible so customizations for hardware differences were no longer necessary. This was the last version of DOS that IBM and Microsoft shared the full code for, and the DOS that was integrated into OS/2 2.0's, and later Windows NT's, virtual DOS machine. PC DOS 6.1 PC DOS remained a rebranded version of MS-DOS until 1993. IBM and Microsoft parted ways—MS-DOS 6 was released in March, and PC DOS 6.1 (separately developed) followed in June. Most of the new features from MS-DOS 6.0 appeared in PC DOS 6.1 including the new boot menu support and the new commands , , and . QBasic was dropped and the MS-DOS Editor was replaced with the IBM E Editor. PC DOS 6.1 reports itself as DOS 6.00. PC DOS 6.3 PC DOS 6.3 followed in December. PC DOS 6.3 was also used in OS/2 for the PowerPC. PC DOS 6.3 also featured SuperStor disk compression technology from Addstor. PC DOS 7 PC DOS 7 was released in April 1995 and was the last release of DOS before IBM software development (other than the development IBM ViaVoice) moved to Austin. The REXX programming language was added, as well as support for a new floppy disk format, XDF, which extended a standard 1.44 MB floppy disk to 1.86 MB. SuperStor disk compression technology was replaced with Stac Electronics' STACKER. An algebraic command line calculator and a utility program to load device drivers from the command line were added. PC DOS 7 also included many optimizations to increase performance and reduce memory usage. PC DOS 2000 The most recent retail release was PC DOS 2000 – released from Austin in 1998 – which found its niche in the embedded software market and elsewhere. PC DOS 2000 is a slipstream of 7.0 with Y2K and other fixes applied. To applications, PC DOS 2000 reports itself as "IBM PC DOS 7.00, revision 1", in contrast to the original PC DOS 7, which reported itself as "IBM PC DOS 7.00, revision 0". Hitachi used PC DOS 2000 in their legacy Drive Fitness Test (4.15) and Hitachi Feature Tool (2.15) until 2009. ThinkPad products had a copy of the latest version of PC DOS in their Rescue and Recovery partition. PC DOS 7.1 PC DOS 7.1 added support for Logical Block Addressing (LBA) and FAT32 partitions. Various builds from 1999 up to 2003 were not released in retail, but used in products such as the IBM ServerGuide Scripting Toolkit. A build of this version of DOS appeared in Norton Ghost from Symantec. Version 7.1 indicates support for FAT32 also in MS-DOS. Most builds of this version of DOS are limited to the kernel files , , and . The updated programs and allow one to prepare FAT32 disks. Additional utilities are taken from PC DOS 2000, where needed. PC DOS as a distributed file client In 1986, IBM announced PC DOS support for client access to the file services defined by Distributed Data Management Architecture (DDM). This enabled programs on PCs to create, manage, and access record-oriented files available on IBM System/36, IBM System/38 and IBM mainframe computers running CICS. In 1988, client support for stream-oriented files and hierarchical directories was added to PC DOS when they became available on the DDM server systems. See also Timeline of DOS operating systems Comparison of DOS operating systems List of DOS commands Notes References Further reading IBM Corporation and Microsoft, Inc. DOS 3.30: User's Guide. IBM Corporation, 1987. Part number 80X0933. IBM Corporation and Microsoft, Inc. DOS 3.30: Reference (Abridged). IBM Corporation, 1987. Part number 94X9575. IBM Corporation. Getting Started with Disk Operating System Version 4.00. IBM Corporation, 1988. Part number 15F1370. IBM Corporation. Using Disk Operating System Version 4.00. IBM Corporation, 1988. Part number 15F1371. IBM Corporation. IBM Disk Operating System Version 5.0. User Guide and Reference. IBM Corporation, 1991. Part number 07G4584. Que Corporation. IBM PC DOS and Microsoft Windows User's Guide. Suzanne Weixel, 2nd ed., Indianapolis, 1995. . IBM Corporation. PC DOS 7 User's Guide. Margaret Averett, 1995. Part number 83G9260 (S83G-9260-00). IBM Corporation. PC DOS 7 Technical Update. IBM Redbooks, 1995. . 1981 software Discontinued operating systems Disk operating systems DOS variants Floppy disk-based operating systems PC DOS Microcomputer software Proprietary operating systems Assembly language software

Operating System (OS)

FreeDOS FreeDOS (formerly Free-DOS and PD-DOS) is a free operating system for IBM PC compatible computers. It intends to provide a complete MS-DOS-compatible environment for running legacy software and supporting embedded systems. FreeDOS can be booted from a floppy disk or USB flash drive. It is designed to run well under virtualization or x86 emulation. Unlike most versions of MS-DOS, FreeDOS is composed of free software, licensed under the terms of the GNU General Public License. However, other packages that form part of the FreeDOS project include non-GPL software considered worthy of preservation, such as 4DOS, which is distributed under a modified MIT License. History The FreeDOS project began on 29 June 1994, after Microsoft announced it would no longer sell or support MS-DOS. Jim Hall – who at the time was a student – posted a manifesto proposing the development of PD-DOS, a public domain version of DOS. Within a few weeks, other programmers including Pat Villani and Tim Norman joined the project. Between them, a kernel (by Villani), the COMMAND.COM command line interpreter (by Villani and Norman), and core utilities (by Hall) were created by pooling code they had written or found available. For some time, the project was maintained by Morgan "Hannibal" Toal. There have been many official pre-release distributions of FreeDOS before the final FreeDOS 1.0 distribution. GNU/DOS, an unofficial distribution of FreeDOS, was discontinued after version 1.0 was released. Blinky the Fish is the mascot of FreeDOS. He was designed by Bas Snabilie. Distribution FreeDOS 1.1, released on 2 January 2012, is available for download as a CD-ROM image: a limited install disc that only contains the kernel and basic applications, and a full disc that contains many more applications (games, networking, development, etc.), not available but with a newer, fuller 1.2. The legacy version 1.0 (2006) consisted of two CDs, one of which was an 8 MB install CD targeted at regular users and the other which was a larger 49 MB live CD that also held the source code of the project. Commercial uses FreeDOS is used by several companies: Dell preloaded FreeDOS with their n-series desktops to reduce their cost. The firm has been criticized for making these machines no cheaper, and harder to buy, than identical systems with Windows. HP provided FreeDOS as an option in its dc5750 desktops, Mini 5101 netbooks and Probook laptops. FreeDOS is also used as bootable media for updating the BIOS firmware in HP systems. FreeDOS is included by Steve Gibson's hard drive maintenance and recovery program, SpinRite. Intel's Solid-State Drive Firmware Update Tool loaded the FreeDOS kernel. Non-commercial uses FreeDOS is also used in multiple independent projects: FED-UP is the Floppy Enhanced DivX Universal Player. FUZOMA is a FreeDOS-based distribution that can boot from a floppy disk and converts older computers into educational tools for children. XFDOS is a FreeDOS-based distribution with a graphical user interface, porting Nano-X and FLTK. Compatibility Hardware FreeDOS requires a PC/XT machine with at least 640 kB of memory. Programs not bundled with FreeDOS often require additional system resources. MS-DOS and Win32 console FreeDOS is mostly compatible with MS-DOS. It supports COM executables, standard DOS executables and Borland's 16-bit DPMI executables. It is also possible to run 32-bit DPMI executables using DOS extenders. The operating system has several improvements relative to MS-DOS, mostly involving support for newer standards and technologies that did not exist when Microsoft ended support for MS-DOS, such as internationalization, or the Advanced Power Management TSRs. Furthermore, with the use of HX DOS Extender, many Windows Console applications function properly in FreeDOS, as do some rare GUI programs, like QEMM and Bochs. DOS-based Windows FreeDOS is able to run Microsoft Windows 1.0 and 2.0 releases. Windows 3.x releases, which had support for i386 processors, cannot fully be run in 386 Enhanced Mode, except partially in the experimental FreeDOS kernel 2037. Windows 95, Windows 98 and Windows Me use a stripped-down version of MS-DOS. FreeDOS cannot be used as a replacement because the undocumented interfaces between MS-DOS 7.0–8.0 and Windows "4.xx" are not emulated by FreeDOS; however, it can be installed and used beside these systems using a boot manager program, such as BOOTMGR or METAKERN included with FreeDOS. Windows NT and ReactOS Windows NT-based operating systems, including Windows 2000, XP, Vista, 7, 10 and 11 for desktops, and Windows Server 2003, 2008 and 2008 R2 for servers, do not make use of MS-DOS as a core component of the system. These systems can make use of the FAT file systems which are used by MS-DOS and earlier versions of Windows; however, they typically use the NTFS (New Technology File System) by default for security and other reasons. FreeDOS can co-exist on these systems on a separate partition or on the same partition on FAT systems. The FreeDOS kernel can be booted by adding it to the Windows 2000 or XP's NT Boot Loader configuration file, boot.ini, or the freeldr.ini equivalent for ReactOS. File systems FAT32 is fully supported and is the preferred format for the boot drive. Depending on the BIOS used, up to four Logical Block Addressing (LBA) hard disks of up to 128 GB, or 2 TB, in size are supported. There has been little testing with large disks, and some BIOSes support LBA but produce errors on disks larger than 32 GB; a driver such as OnTrack or EZ-Drive resolves this problem. FreeDOS can also be used with a driver called LFNDOS to enable support for Windows 95-style long file names, but most pre-Windows 95 programs do not support LFNs, even with a driver loaded. There is no planned support for NTFS, ext2 or exFAT, but there are several external third-party drivers available for that purpose. To access ext2 file systems, LTOOLS, a counterpart to Mtools, can sometimes be used to copy data to and from ext2 file system drives. See also Arachne DOSBox DOSEMU FreeRTOS GNU GRUB ReactOS VFAT References External links FreeDOS Orphanage 1998 software DOS variants Embedded operating systems Floppy disk-based operating systems Free software operating systems Free software programmed in C Microcomputer software Operating system distributions bootable from read-only media Software using the GPL license

Operating System (OS)

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 2000 for professional users and Windows Me for home users. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. Development of Windows XP began in the late 1990s under the codename "Neptune", built on the Windows NT kernel explicitly intended for mainstream consumer use. An updated version of Windows 2000 was also initially planned for the business market. However, in January 2000, both projects were scrapped in favor of a single OS codenamed "Whistler", which would serve as a single platform for both consumer and business markets. As a result, Windows XP is the first consumer edition of Windows not based on the Windows 95 kernel and MS-DOS. Upon its release, Windows XP received critical acclaim, noting increased performance and stability (especially compared to Windows Me), a more intuitive user interface, improved hardware support, and expanded multimedia capabilities. However, some industry reviewers were concerned by the new licensing model and product activation system. Windows XP and Windows Server 2003 were succeeded by Windows Vista and Windows Server 2008, released in 2007 and 2008, respectively. Market share of Windows XP fell below 1% by the end of 2021, right when Windows 10 was released Mainstream support for Windows XP ended on April 14, 2009, and extended support ended on April 8, 2014. After that, the operating system ceased receiving further support. Windows Embedded POSReady 2009, based on Windows XP Professional, received security updates until April 2019. After that, unofficial methods were made available to apply the updates to other editions of Windows XP. Still, Microsoft discouraged this practice, citing incompatibility issues. , 0.5% of Windows PCs run Windows XP (on all continents, the share is below 1%), and 0.18% of all devices across all platforms run Windows XP. Windows XP is still very prevalent in many countries, such as Armenia, where 50–60% of computers use it. Development In the late 1990s, initial development of what would become Windows XP was focused on two individual products: "Odyssey", which was reportedly intended to succeed the future Windows 2000; and "Neptune", which was reportedly a consumer-oriented operating system using the Windows NT architecture, succeeding the MS-DOS-based Windows 98. However, the projects proved to be too ambitious. In January 2000, shortly prior to the official release of Windows 2000, technology writer Paul Thurrott reported that Microsoft had shelved both Neptune and Odyssey in favor of a new product codenamed "Whistler", named after Whistler, British Columbia, as many Microsoft employees skied at the Whistler-Blackcomb ski resort. The goal of Whistler was to unify both the consumer and business-oriented Windows lines under a single, Windows NT platform: Thurrott stated that Neptune had become "a black hole when all the features that were cut from Windows Me were simply re-tagged as Neptune features. And since Neptune and Odyssey would be based on the same code-base anyway, it made sense to combine them into a single project". At PDC on July 13, 2000, Microsoft announced that Whistler would be released during the second half of 2001, and also unveiled the first preview build, 2250, which featured an early implementation of Windows XP's visual styles system and interface changes to Windows Explorer and the Control Panel. Microsoft released the first public beta build of Whistler, build 2296, on October 31, 2000. Subsequent builds gradually introduced features that users of the release version of Windows XP would recognize, such as Internet Explorer 6.0, the Microsoft Product Activation system and the Bliss desktop background. Whistler was officially unveiled during a media event on February 5, 2001, under the name Windows XP, where XP stands for "eXPerience". Release In June 2001, Microsoft indicated that it was planning to, in conjunction with Intel and other PC makers, spend at least 1 billion US dollars on marketing and promoting Windows XP. The theme of the campaign, "Yes You Can", was designed to emphasize the platform's overall capabilities. Microsoft had originally planned to use the slogan "Prepare to Fly", but it was replaced because of sensitivity issues in the wake of the September 11 attacks. On August 24, 2001, Windows XP build 2600 was released to manufacturing (RTM). During a ceremonial media event at Microsoft Redmond Campus, copies of the RTM build were given to representatives of several major PC manufacturers in briefcases, who then flew off on decorated helicopters. While PC manufacturers would be able to release devices running XP beginning on September 24, 2001, XP was expected to reach general, retail availability on October 25, 2001. On the same day, Microsoft also announced the final retail pricing of XP's two main editions, "Home" (as a replacement for Windows Me for home computing) and "Professional" (as a replacement for Windows 2000 for high-end users). New and updated features User interface While retaining some similarities to previous versions, Windows XP's interface was overhauled with a new visual appearance, with an increased use of alpha compositing effects, drop shadows, and "visual styles", which completely changed the appearance of the operating system. The number of effects enabled are determined by the operating system based on the computer's processing power, and can be enabled or disabled on a case-by-case basis. XP also added ClearType, a new subpixel rendering system designed to improve the appearance of fonts on liquid-crystal displays. A new set of system icons was also introduced. The default wallpaper, Bliss, is a photo of a landscape in the Napa Valley outside Napa, California, with rolling green hills and a blue sky with stratocumulus and cirrus clouds. The Start menu received its first major overhaul in XP, switching to a two-column layout with the ability to list, pin, and display frequently used applications, recently opened documents, and the traditional cascading "All Programs" menu. The taskbar can now group windows opened by a single application into one taskbar button, with a popup menu listing the individual windows. The notification area also hides "inactive" icons by default. A "common tasks" list was added, and Windows Explorer's sidebar was updated to use a new task-based design with lists of common actions; the tasks displayed are contextually relevant to the type of content in a folder (e.g. a folder with music displays offers to play all the files in the folder, or burn them to a CD). Fast user switching allows additional users to log into a Windows XP machine without existing users having to close their programs and log out. Although only one user at the time can use the console (i.e. monitor, keyboard, and mouse), previous users can resume their session once they regain control of the console. Infrastructure Windows XP uses prefetching to improve startup and application launch times. It also became possible to revert the installation of an updated device driver, should the updated driver produce undesirable results. A copy protection system known as Windows Product Activation was introduced with Windows XP and its server counterpart, Windows Server 2003. All Windows licenses must be tied to a unique ID generated using information from the computer hardware, transmitted either via the internet or a telephone hotline. If Windows is not activated within 30 days of installation, the OS will cease to function until it is activated. Windows also periodically verifies the hardware to check for changes. If significant hardware changes are detected, the activation is voided, and Windows must be re-activated. Networking and internet functionality Windows XP was originally bundled with Internet Explorer 6, Outlook Express 6, Windows Messenger, and MSN Explorer. New networking features were also added, including Internet Connection Firewall, Internet Connection Sharing integration with UPnP, NAT traversal APIs, Quality of Service features, IPv6 and Teredo tunneling, Background Intelligent Transfer Service, extended fax features, network bridging, peer to peer networking, support for most DSL modems, IEEE 802.11 (Wi-Fi) connections with auto configuration and roaming, TAPI 3.1, and networking over FireWire. Remote Assistance and Remote Desktop were also added, which allow users to connect to a computer running Windows XP from across a network or the Internet and access their applications, files, printers, and devices or request help. Improvements were also made to IntelliMirror features such as Offline Files, Roaming user profiles and Folder redirection. Backwards compatibility To enable running software that targets or locks out specific versions of Windows, "Compatibility mode" has been added. The feature allows pretending a selected earlier version of Windows to software, starting at Windows 95. While this ability was first introduced in Windows 2000 Service Pack 2, it had to be activated through the "register server" and was only available to administrator users, whereas Windows XP has it activated out of the box and also grants it to regular users. Other features Improved application compatibility and shims compared to Windows 2000. DirectX 8.1, upgradeable to DirectX 9.0c. A number of new features in Windows Explorer including task panes, thumbnails, and the option to view photos as a slideshow. Improved imaging features such as Windows Picture and Fax Viewer. Faster start-up, (because of improved Prefetch functions) logon, logoff, hibernation, and application launch sequences. Numerous improvements to increase the system reliability such as improved System Restore, Automated System Recovery, and driver reliability improvements through Device Driver Rollback. Hardware support improvements such as FireWire 800, and improvements to multi-monitor support under the name "DualView". Fast user switching. The ClearType font rendering mechanism, which is designed to improve text readability on liquid-crystal display (LCD) and similar monitors, especially laptops. Side-by-side assemblies and registration-free COM. General improvements to international support such as more locales, languages and scripts, MUI support in Terminal Services, improved Input Method Editors, and National Language Support. Removed features Some of the programs and features that were part of the previous versions of Windows did not make it to Windows XP. Various MS-DOS commands available in its Windows 9x predecessor were removed, as were the POSIX and OS/2 subsystems. In networking, NetBEUI, NWLink and NetDDE were deprecated and not installed by default. Plug-and-play–incompatible communication devices (like modems and network interface cards) were no longer supported. Service Pack 2 and Service Pack 3 also removed features from Windows XP, but to a less noticeable extent. For instance, support for TCP half-open connections was removed in Service Pack 2, and the address bar on the taskbar was removed in Service Pack 3. Editions Windows XP was released in two major editions on launch: Home Edition and Professional Edition. Both editions were made available at retail as pre-loaded software on new computers and as boxed copies. Boxed copies were sold as "Upgrade" or "Full" licenses; the "Upgrade" versions were slightly cheaper, but require an existing version of Windows to install. The "Full" version can be installed on systems without an operating system or existing version of Windows. The two editions of XP were aimed at different markets: Home Edition is explicitly intended for consumer use and disables or removes certain advanced and enterprise-oriented features present on Professional, such as the ability to join a Windows domain, Internet Information Services, and Multilingual User Interface. Windows 98 or Me can be upgraded to either edition, but Windows NT 4.0 and Windows 2000 can only be upgraded to Professional. Windows' software license agreement for pre-loaded licenses allows the software to be "returned" to the OEM for a refund if the user does not wish to use it. Despite the refusal of some manufacturers to honor the entitlement, it has been enforced by courts in some countries. Two specialized variants of XP were introduced in 2002 for certain types of hardware, exclusively through OEM channels as pre-loaded software. Windows XP Media Center Edition was initially designed for high-end home theater PCs with TV tuners (marketed under the term "Media Center PC"), offering expanded multimedia functionality, an electronic program guide, and digital video recorder (DVR) support through the Windows Media Center application. Microsoft also unveiled Windows XP Tablet PC Edition, which contains additional pen input features, and is optimized for mobile devices meeting its Tablet PC specifications. Two different 64-bit editions of XP were made available. The first, Windows XP 64-Bit Edition, was intended for IA-64 (Itanium) systems; as IA-64 usage declined on workstations in favor of AMD's x86-64 architecture, the Itanium edition was discontinued in January 2005. A new 64-bit edition supporting the x86-64 architecture, called Windows XP Professional x64 Edition, was released in April of the same year. Microsoft also targeted emerging markets with the 2004 introduction of Windows XP Starter Edition, a special variant of Home Edition intended for low-cost PCs. The OS is primarily aimed at first-time computer owners, containing heavy localization (including wallpapers and screen savers incorporating images of local landmarks), and a "My Support" area which contains video tutorials on basic computing tasks. It also removes certain "complex" features, and does not allow users to run more than three applications at a time. After a pilot program in India and Thailand, Starter was released in other emerging markets throughout 2005. In 2006, Microsoft also unveiled the FlexGo initiative, which would also target emerging markets with subsidized PCs on a pre-paid, subscription basis. As a result of unfair competition lawsuits in Europe and South Korea, which both alleged that Microsoft had improperly leveraged its status in the PC market to favor its own bundled software, Microsoft was ordered to release special editions of XP in these markets that excluded certain applications. In March 2004, after the European Commission fined Microsoft €497 million (US$603 million), Microsoft was ordered to release "N" editions of XP that excluded Windows Media Player, encouraging users to pick and download their own media player software. As it was sold at the same price as the edition with Windows Media Player included, certain OEMs (such as Dell, who offered it for a short period, along with Hewlett-Packard, Lenovo and Fujitsu Siemens) chose not to offer it. Consumer interest was minuscule, with roughly 1,500 units shipped to OEMs, and no reported sales to consumers. In December 2005, the Korean Fair Trade Commission ordered Microsoft to make available editions of Windows XP and Windows Server 2003 that do not contain Windows Media Player or Windows Messenger. The "K" and "KN" editions of Windows XP were released in August 2006, and are only available in English and Korean, and also contain links to third-party instant messenger and media player software. Service packs A service pack is a cumulative update package that is a superset of all updates, and even service packs, that have been released before it. Three service packs have been released for Windows XP. Service Pack 3 is slightly different, in that it needs at least Service Pack 1 to have been installed, in order to update a live OS. However, Service Pack 3 can still be embedded into a Windows installation disc; SP1 is not reported as a prerequisite for doing so. Service Pack 1 Service Pack 1 (SP1) for Windows XP was released on September 9, 2002. It contained over 300 minor, post-RTM bug fixes, along with all security patches released since the original release of XP. SP1 also added USB 2.0 support, the Microsoft Java Virtual Machine, .NET Framework support, and support for technologies used by the then-upcoming Media Center and Tablet PC editions of XP. The most significant change on SP1 was the addition of Set Program Access and Defaults, a settings page which allows programs to be set as default for certain types of activities (such as media players or web browsers) and for access to bundled, Microsoft programs (such as Internet Explorer or Windows Media Player) to be disabled. This feature was added to comply with the settlement of United States v. Microsoft Corp., which required Microsoft to offer the ability for OEMs to bundle third-party competitors to software it bundles with Windows (such as Internet Explorer and Windows Media Player), and give them the same level of prominence as those normally bundled with the OS. On February 3, 2003, Microsoft released Service Pack 1a (SP1a). It was the same as SP1, except, the Microsoft Java Virtual Machine was excluded. Service Pack 2 Service Pack 2 (SP2) for Windows XP Home edition and Professional edition was released on August 25, 2004. Headline features included WPA encryption compatibility for Wi-Fi and usability improvements to the Wi-Fi networking user interface, partial Bluetooth support, and various improvements to security systems. The security improvements (codenamed "Springboard", as these features were intended to underpin additional changes in Longhorn) included a major revision to the included firewall (renamed Windows Firewall, and now enabled by default), and an update to Data Execution Prevention, which gained hardware support in the NX bit that can stop some forms of buffer overflow attacks. Raw socket support is removed (which supposedly limits the damage done by zombie machines) and the Windows Messenger service (which had been abused to cause pop-up advertisements to be displayed as system messages without a web browser or any additional software) became disabled by default. Additionally, security-related improvements were made to e-mail and web browsing. Service Pack 2 also added Security Center, an interface that provides a general overview of the system's security status, including the state of the firewall and automatic updates. Third-party firewall and antivirus software can also be monitored from Security Center. The unique boot screens that identified the edition of Windows XP currently running, including a green progress bar for Home Edition and a blue progress bar for other editions, were removed and replaced with a generic "Windows XP" boot screen with a blue progress bar with this service pack. In August 2006, Microsoft released updated installation media for Windows XP and Windows Server 2003 SP2 (SP2b), in order to incorporate a patch requiring ActiveX controls in Internet Explorer to be manually activated before a user may interact with them. This was done so that the browser would not violate a patent owned by Eolas. Microsoft has since licensed the patent, and released a patch reverting the change in April 2008. In September 2007, another minor revision known as SP2c was released for XP Professional, extending the number of available product keys for the operating system to "support the continued availability of Windows XP Professional through the scheduled system builder channel end-of-life (EOL) date of January 31, 2009." Service Pack 3 The third and final Service Pack, SP3, was released through different channels between April and June 2008, about a year after the release of Windows Vista, and about a year before the release of Windows 7. Service Pack 3 was not available for Windows XP x64 Edition, which was based on the Windows Server 2003 kernel and, as a result, used its service packs rather than the ones for the other editions. It began being automatically pushed out to Automatic Updates users on July 10, 2008. A feature set overview which detailed new features available separately as stand-alone updates to Windows XP, as well as backported features from Windows Vista, was posted by Microsoft. A total of 1,174 fixes are included in SP3. Service Pack 3 could be installed on systems with Internet Explorer versions 6, 7, or 8; Internet Explorer 7 was not included as part of SP3. Service Pack 3 included security enhancements over and above those of SP2, including APIs allowing developers to enable Data Execution Prevention for their code, independent of system-wide compatibility enforcement settings, the Security Support Provider Interface, improvements to WPA2 security, and an updated version of the Microsoft Enhanced Cryptographic Provider Module that is FIPS 140-2 certified. In incorporating all previously released updates not included in SP2, Service Pack 3 included many other key features. Windows Imaging Component allowed camera vendors to integrate their own proprietary image codecs with the operating system's features, such as thumbnails and slideshows. In enterprise features, Remote Desktop Protocol 6.1 included support for ClearType and 32-bit color depth over RDP, while improvements made to Windows Management Instrumentation in Windows Vista to reduce the possibility of corruption of the WMI repository were backported to XP SP3. In addition, SP3 contains updates to the operating system components of Windows XP Media Center Edition (MCE) and Windows XP Tablet PC Edition, and security updates for .NET Framework version 1.0, which is included in these editions. However, it does not include update rollups for the Windows Media Center application in Windows XP MCE 2005. SP3 also omits security updates for Windows Media Player 10, although the player is included in Windows XP MCE 2005. The Address Bar DeskBand on the Taskbar is no longer included because of antitrust violation concerns. Unofficial SP3 ZIP download packages were released on a now-defunct website called The Hotfix from 2005 to 2007. The owner of the website, Ethan C. Allen, was a former Microsoft employee in Software Quality Assurance and would comb through the Microsoft Knowledge Base articles daily and download new hotfixes Microsoft would put online within the articles. The articles would have a "kbwinxppresp3fix" and/or "kbwinxpsp3fix" tag, thus allowing Allen to easily find and determine which fixes were planned for the official SP3 release to come. Microsoft publicly stated at the time that the SP3 pack was unofficial and users should not install it. Allen also released a Vista SP1 package in 2007, for which Allen received a cease-and-desist email from Microsoft. System requirements System requirements for Windows XP are as follows: Notes Physical memory limits The maximum amount of RAM that Windows XP can support varies depending on the product edition and the processor architecture. Most 32-bit editions of XP support up to 4 GB, with the exception of Windows XP Starter, which is limited to 512 MB. 64-bit editions support up to 128 GB. Processor limits Windows XP Professional supports up to two physical processors; Windows XP Home Edition is limited to one. However, XP supports a greater number of logical processors: 32-bit editions support up to 32 logical processors, whereas 64-bit editions support up to 64 logical processors. Support lifecycle Support for the original release of Windows XP (without a service pack) ended on August 30, 2005. Both Windows XP Service Pack 1 and 1a were retired on October 10, 2006, and both Windows 2000 and Windows XP SP2 reached their end of support on July 13, 2010, about 24 months after the launch of Windows XP Service Pack 3. The company stopped general licensing of Windows XP to OEMs and terminated retail sales of the operating system on June 30, 2008, 17 months after the release of Windows Vista. However, an exception was announced on April 3, 2008, for OEMs producing what it defined as "ultra low-cost personal computers", particularly netbooks, until one year after the availability of Windows 7 on October 22, 2010. Analysts felt that the move was primarily intended to compete against Linux-based netbooks, although Microsoft's Kevin Hutz stated that the decision was due to apparent market demand for low-end computers with Windows. Variants of Windows XP for embedded systems have different support policies: Windows XP Embedded SP3 and Windows Embedded for Point of Service SP3 were supported until January and April 2016, respectively. Windows Embedded Standard 2009, which was succeeded by Windows Embedded Standard 7, and Windows Embedded POSReady 2009, which was succeeded by Windows Embedded POSReady 7, were supported until January and April 2019, respectively. These updates, while intended for the embedded editions, could also be downloaded on standard Windows XP with a registry hack, which enabled unofficial patches until April 2019. However, Microsoft advised Windows XP users against installing these fixes, citing incompatibility issues. End of support On April 14, 2009, Windows XP exited mainstream support and entered the extended support phase; Microsoft continued to provide security updates every month for Windows XP, however, free technical support, warranty claims, and design changes were no longer being offered. Extended support ended on April 8, 2014, over 12 years after the release of Windows XP; normally Microsoft products have a support life cycle of only 10 years. Beyond the final security updates released on April 8, no more security patches or support information are provided for XP free-of-charge; "critical patches" will still be created, and made available only to customers subscribing to a paid "Custom Support" plan. As it is a Windows component, all versions of Internet Explorer for Windows XP also became unsupported. In January 2014, it was estimated that more than 95% of the 3 million automated teller machines in the world were still running Windows XP (which largely replaced IBM's OS/2 as the predominant operating system on ATMs); ATMs have an average lifecycle of between seven and ten years, but some have had lifecycles as long as 15. Plans were being made by several ATM vendors and their customers to migrate to Windows 7-based systems over the course of 2014, while vendors have also considered the possibility of using Linux-based platforms in the future to give them more flexibility for support lifecycles, and the ATM Industry Association (ATMIA) has since endorsed Windows 10 as a further replacement. However, ATMs typically run the embedded variant of Windows XP, which was supported through January 2016. As of May 2017, around 60% of the 220,000 ATMs in India still run Windows XP. Furthermore, at least 49% of all computers in China still ran XP at the beginning of 2014. These holdouts were influenced by several factors; prices of genuine copies of later versions of Windows in the country are high, while Ni Guangnan of the Chinese Academy of Sciences warned that Windows 8 could allegedly expose users to surveillance by the United States government, and the Chinese government would ban the purchase of Windows 8 products for government use in May 2014 in protest of Microsoft's inability to provide "guaranteed" support. The government also had concerns that the impending end of support could affect their anti-piracy initiatives with Microsoft, as users would simply pirate newer versions rather than purchasing them legally. As such, government officials formally requested that Microsoft extend the support period for XP for these reasons. While Microsoft did not comply with their requests, a number of major Chinese software developers, such as Lenovo, Kingsoft and Tencent, will provide free support and resources for Chinese users migrating from XP. Several governments, in particular those of the Netherlands and the United Kingdom, elected to negotiate "Custom Support" plans with Microsoft for their continued, internal use of Windows XP; the British government's deal lasted for a year, and also covered support for Office 2003 (which reached end-of-life the same day) and cost £5.5 million. On March 8, 2014, Microsoft deployed an update for XP that, on the 8th of each month, displays a pop-up notification to remind users about the end of support; however, these notifications may be disabled by the user. Microsoft also partnered with Laplink to provide a special "express" version of its PCmover software to help users migrate files and settings from XP to a computer with a newer version of Windows. Despite the approaching end of support, there were still notable holdouts that had not migrated past XP; many users elected to remain on XP because of the poor reception of Windows Vista, sales of newer PCs with newer versions of Windows declined because of the Great Recession and the effects of Vista, and deployments of new versions of Windows in enterprise environments require a large amount of planning, which includes testing applications for compatibility (especially those that are dependent on Internet Explorer 6, which is not compatible with newer versions of Windows). Major security software vendors (including Microsoft itself) planned to continue offering support and definitions for Windows XP past the end of support to varying extents, along with the developers of Google Chrome, Mozilla Firefox, and Opera web browsers; despite these measures, critics similarly argued that users should eventually migrate from XP to a supported platform. The United States' Computer Emergency Readiness Team released an alert in March 2014 advising users of the impending end of support, and informing them that using XP after April 8 may prevent them from meeting US government information security requirements. Microsoft continued to provide Security Essentials virus definitions and updates for its Malicious Software Removal Tool (MSRT) for XP until July 14, 2015. As the end of extended support approached, Microsoft began to increasingly urge XP customers to migrate to newer versions such as Windows 7 or 8 in the interest of security, suggesting that attackers could reverse engineer security patches for newer versions of Windows and use them to target equivalent vulnerabilities in XP. Windows XP is remotely exploitable by numerous security holes that were discovered after Microsoft stopped supporting it. Similarly, specialized devices that run XP, particularly medical devices, must have any revisions to their software—even security updates for the underlying operating system—approved by relevant regulators before they can be released. For this reason, manufacturers often did not allow any updates to devices' operating systems, leaving them open to security exploits and malware. Despite the end of support for Windows XP, Microsoft has released three emergency security updates for the operating system to patch major security vulnerabilities: A patch released in May 2014 to address recently discovered vulnerabilities in Internet Explorer 6 through 11 on all versions of Windows. A patch released in May 2017 to address a vulnerability that was being leveraged by the WannaCry ransomware attack. A patch released in May 2019 to address a critical code execution vulnerability in Remote Desktop Services which can be exploited in a similar way as the WannaCry vulnerability. Researchers reported in August 2019 that Windows 10 users may be at risk for "critical" system compromise because of design flaws of hardware device drivers from multiple providers. In the same month, computer experts reported that the BlueKeep security vulnerability, , that potentially affects older unpatched Microsoft Windows versions via the program's Remote Desktop Protocol, allowing for the possibility of remote code execution, may now include related flaws, collectively named DejaBlue, affecting newer Windows versions (i.e., Windows 7 and all recent versions) as well. In addition, experts reported a Microsoft security vulnerability, , based on legacy code involving Microsoft CTF and ctfmon (ctfmon.exe), that affects all Windows versions from the older Windows XP version to the most recent Windows 10 versions; a patch to correct the flaw is currently available. Microsoft announced in July 2019 that the Microsoft Internet Games services on Windows XP and Windows Me would end on July 31, 2019 (and for Windows 7 on January 22, 2020). Others, such as Steam, had done the same, ending support for Windows XP and Windows Vista in January 2019. In 2020, Microsoft announced that it would disable the Windows Update service for SHA-1 endpoints; since Windows XP did not get an update for SHA-2, Windows Update Services are no longer available on the OS as of late July 2020. However, as of October 2021, the old updates for Windows XP are still available on the Microsoft Update Catalog. Reception On release, Windows XP received critical acclaim. CNET described the operating system as being "worth the hype", considering the new interface to be "spiffier" and more intuitive than previous versions, but feeling that it may "annoy" experienced users with its "hand-holding". XP's expanded multimedia support and CD burning functionality were also noted, along with its streamlined networking tools. The performance improvements of XP in comparison to 2000 and Me were also praised, along with its increased number of built-in device drivers in comparison to 2000. The software compatibility tools were also praised, although it was noted that some programs, particularly older MS-DOS software, may not work correctly on XP because of its differing architecture. They panned Windows XP's new licensing model and product activation system, considering it to be a "slightly annoying roadblock", but acknowledged Microsoft's intent for the changes. PC Magazine provided similar praise, although noting that a number of its online features were designed to promote Microsoft-owned services, and that aside from quicker boot times, XP's overall performance showed little difference over Windows 2000. Windows XP's default theme, Luna, was criticized by some users for its childish look. Despite extended support for Windows XP ending in 2014, many users – including some enterprises – were reluctant to move away from an operating system they viewed as a stable known quantity despite the many security and functionality improvements in subsequent releases of Windows. Windows XP's longevity was viewed as testament to its stability and Microsoft's successful attempts to keep it up to date, but also as an indictment of its direct successor's perceived failings. Market share According to web analytics data generated by Net Applications, Windows XP was the most widely used operating system until August 2012, when Windows 7 overtook it (later overtaken by Windows 10), while StatCounter indicates it happening almost a year earlier. In January 2014, Net Applications reported a market share of 29.23% of "desktop operating systems" for XP (when XP was introduced there was not a separate mobile category to track), while W3Schools reported a share of 11.0%. , in most regions or continents, Windows XP market share on PCs, as a fraction of the total Windows share, has gone below 1% (1.72% in Africa, where it was previously at 0.8%). XP still has a double-digit market share in a few countries, such as Armenia at over 50%, at 57%, where Windows 7 was highest ranked, and with it being replaced by Windows 10, Windows XP got highest ranked for the longest time, and had over 60% share on some weekends in summer of 2019. Source code leak On September 23, 2020, source code for Windows XP with Service Pack 1 and Windows Server 2003 was leaked onto the imageboard 4chan by an unknown user. Anonymous users managed to compile the code, as well as a Twitter user who posted videos of the process on YouTube proving that the code was genuine. The videos were later removed on copyright grounds by Microsoft. The leak was incomplete as it was missing the Winlogon source code and some other components. The original leak itself was spread using magnet links and torrent files whose payload originally included Server 2003 and XP source code and which was later updated with additional files, among which were previous leaks of Microsoft products, its patents, media about conspiracy theories on Bill Gates by anti-vaccination movements and an assortment of PDF files on different topics. Microsoft issued a statement stating that it was investigating the leaks. See also BlueKeep (security vulnerability) Comparison of operating systems History of operating systems List of operating systems References Further reading External links Windows XP End of Support Security Update for Windows XP SP3 (KB4012598) 2001 software Products and services discontinued in 2014 XP IA-32 operating systems Obsolete technologies

Operating System (OS)

TRIPOS TRIPOS (TRIvial Portable Operating System) is a computer operating system. Development started in 1976 at the Computer Laboratory of Cambridge University and it was headed by Dr. Martin Richards. The first version appeared in January 1978 and it originally ran on a PDP-11. Later it was ported to the Computer Automation LSI4 and the Data General Nova. Work on a Motorola 68000 version started in 1981 at the University of Bath. MetaComCo acquired the rights to the 68000 version and continued development until TRIPOS was chosen by Commodore Amiga in March 1985 to form part of an operating system for their new computer; it was also used at Cambridge as part of the Cambridge Distributed Computing System. Students in the Computer Science department at Cambridge affectionately refer to TRIPOS as the Terribly Reliable, Incredibly Portable Operating System. The name TRIPOS also refers to the Tripos system of undergraduate courses and examinations, which is unique to Cambridge University. Influences on the Amiga computer In July 1985, the Amiga was introduced, incorporating TRIPOS in the AmigaDOS module of AmigaOS. AmigaDOS included a command line interface and the Amiga File System. The entire AmigaDOS module was originally written in BCPL (an ancestor of the C programming language), the same language used to write TRIPOS. AmigaDOS would later be rewritten in C from AmigaOS 2.x onwards, retaining backwards compatibility with 1.x up until AmigaOS 4 (completely rewritten in C) when AmigaDOS abandoned its BCPL legacy. Features TRIPOS provided features such as pre-emptive multi-tasking (using strict-priority scheduling), a hierarchical file system and multiple command line interpreters. The most important TRIPOS concepts have been the non-memory-management approach (meaning no checks are performed to stop programs from using unallocated memory) and message passing by means of passing pointers instead of copying message contents. Those two concepts together allowed for sending and receiving over 1250 packets per second on a 10 MHz Motorola 68010 CPU. Most of TRIPOS was implemented in BCPL. The kernel and device drivers were implemented in assembly language. One notable feature of TRIPOS/BCPL was its cultural use of shared libraries, untypical at the time, resulting in small and therefore fast loading utilities. For example, many of the standard system utilities were well below 0.5 Kbytes in size, compared to a typical minimum of about 20 Kbytes for functionally equivalent code on a modern Unix or Linux. TRIPOS was ported to a number of machines, including the Data General Nova 2, the Computer Automation LSI4, Motorola 68000 and Intel 8086- based hardware. It included support for the Cambridge Ring local area network. More recently, Martin Richards produced a port of TRIPOS to run under Linux, using Cintcode BCPL virtual machine. As of February 2020, TRIPOS is still actively maintained by Open G I Ltd. (formerly Misys Financial Systems) in Worcestershire, UK. Many British insurance brokers have a Linux/Intel based TRIPOS system serving networked workstations over a TCP/IP connection - the systems are used to run Open G I's BROOMS Application suite. Open G I have added a number of features to support the modern office such as the ability to integrate into many mainstream applications and services such as SQL server, Citrix XENAPP, terminal servers, etc. Commands The following list of commands is supported by the TRIPOS CLI. ALINK ASSEM ASSIGN BREAK C CD CONSOLE COPY DATE DELETE DIR DISKCOPY DISKDOCTOR ECHO ED EDIT ENDCLI FAILAT FAULT FILENOTE FORMAT IF INFO INSTALL JOIN LAB LIST MAKEDIR MOUNT NEWCLI PATH PROMPT PROTECT QUIT RELABEL RENAME RUN SEARCH SKIP SORT STACK STATUS TYPE VDU WAIT WHY Cintpos Cintpos is an experimental interpretive version of TRIPOS which runs on the Cintcode BCPL virtual machine, also developed by Martin Richards. References Reference manuals Martin Richards' Cintpos page A brief informal history of the Computer Laboratory In the beginning was CAOS Further reading External links Amiga history guide: TripOS/68k CBG Stallone Computer Amiga Computer-related introductions in 1978 Discontinued operating systems History of computing in the United Kingdom University of Cambridge Computer Laboratory

Operating System (OS)

Kernel (operating system) The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system. It is the portion of the operating system code that is always resident in memory, and facilitates interactions between hardware and software components. A full kernel controls all hardware resources (e.g. I/O, memory, cryptography) via device drivers, arbitrates conflicts between processes concerning such resources, and optimizes the utilization of common resources e.g. CPU & cache usage, file systems, and network sockets. On most systems, the kernel is one of the first programs loaded on startup (after the bootloader). It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit. The critical code of the kernel is usually loaded into a separate area of memory, which is protected from access by application software or other less critical parts of the operating system. The kernel performs its tasks, such as running processes, managing hardware devices such as the hard disk, and handling interrupts, in this protected kernel space. In contrast, application programs such as browsers, word processors, or audio or video players use a separate area of memory, user space. This separation prevents user data and kernel data from interfering with each other and causing instability and slowness, as well as preventing malfunctioning applications from affecting other applications or crashing the entire operating system. Even in systems where the kernel is included in application address spaces, memory protection is used to prevent unauthorized applications from modifying the kernel. The kernel's interface is a low-level abstraction layer. When a process requests a service from the kernel, it must invoke a system call, usually through a wrapper function. There are different kernel architecture designs. Monolithic kernels run entirely in a single address space with the CPU executing in supervisor mode, mainly for speed. Microkernels run most but not all of their services in user space, like user processes do, mainly for resilience and modularity. MINIX 3 is a notable example of microkernel design. Instead, the Linux kernel is monolithic, although it is also modular, for it can insert and remove loadable kernel modules at runtime. This central component of a computer system is responsible for executing programs. The kernel takes responsibility for deciding at any time which of the many running programs should be allocated to the processor or processors. Random-access memory Random-access memory (RAM) is used to store both program instructions and data. Typically, both need to be present in memory in order for a program to execute. Often multiple programs will want access to memory, frequently demanding more memory than the computer has available. The kernel is responsible for deciding which memory each process can use, and determining what to do when not enough memory is available. Input/output devices I/O devices include such peripherals as keyboards, mice, disk drives, printers, USB devices, network adapters, and display devices. The kernel allocates requests from applications to perform I/O to an appropriate device and provides convenient methods for using the device (typically abstracted to the point where the application does not need to know implementation details of the device). Resource management Key aspects necessary in resource management are defining the execution domain (address space) and the protection mechanism used to mediate access to the resources within a domain. Kernels also provide methods for synchronization and inter-process communication (IPC). These implementations may be located within the kernel itself or the kernel can also rely on other processes it is running. Although the kernel must provide IPC in order to provide access to the facilities provided by each other, kernels must also provide running programs with a method to make requests to access these facilities. The kernel is also responsible for context switching between processes or threads. Memory management The kernel has full access to the system's memory and must allow processes to safely access this memory as they require it. Often the first step in doing this is virtual addressing, usually achieved by paging and/or segmentation. Virtual addressing allows the kernel to make a given physical address appear to be another address, the virtual address. Virtual address spaces may be different for different processes; the memory that one process accesses at a particular (virtual) address may be different memory from what another process accesses at the same address. This allows every program to behave as if it is the only one (apart from the kernel) running and thus prevents applications from crashing each other. On many systems, a program's virtual address may refer to data which is not currently in memory. The layer of indirection provided by virtual addressing allows the operating system to use other data stores, like a hard drive, to store what would otherwise have to remain in main memory (RAM). As a result, operating systems can allow programs to use more memory than the system has physically available. When a program needs data which is not currently in RAM, the CPU signals to the kernel that this has happened, and the kernel responds by writing the contents of an inactive memory block to disk (if necessary) and replacing it with the data requested by the program. The program can then be resumed from the point where it was stopped. This scheme is generally known as demand paging. Virtual addressing also allows creation of virtual partitions of memory in two disjointed areas, one being reserved for the kernel (kernel space) and the other for the applications (user space). The applications are not permitted by the processor to address kernel memory, thus preventing an application from damaging the running kernel. This fundamental partition of memory space has contributed much to the current designs of actual general-purpose kernels and is almost universal in such systems, although some research kernels (e.g., Singularity) take other approaches. Device management To perform useful functions, processes need access to the peripherals connected to the computer, which are controlled by the kernel through device drivers. A device driver is a computer program encapsulating, monitoring and controlling a hardware device (via its Hardware/Software Interface (HSI)) on behalf of the OS. It provides the operating system with an API, procedures and information about how to control and communicate with a certain piece of hardware. Device drivers are an important and vital dependency for all OS and their applications. The design goal of a driver is abstraction; the function of the driver is to translate the OS-mandated abstract function calls (programming calls) into device-specific calls. In theory, a device should work correctly with a suitable driver. Device drivers are used for e.g. video cards, sound cards, printers, scanners, modems, and Network cards. At the hardware level, common abstractions of device drivers include: Interfacing directly Using a high-level interface (Video BIOS) Using a lower-level device driver (file drivers using disk drivers) Simulating work with hardware, while doing something entirely different And at the software level, device driver abstractions include: Allowing the operating system direct access to hardware resources Only implementing primitives Implementing an interface for non-driver software such as TWAIN Implementing a language (often a high-level language such as PostScript) For example, to show the user something on the screen, an application would make a request to the kernel, which would forward the request to its display driver, which is then responsible for actually plotting the character/pixel. A kernel must maintain a list of available devices. This list may be known in advance (e.g., on an embedded system where the kernel will be rewritten if the available hardware changes), configured by the user (typical on older PCs and on systems that are not designed for personal use) or detected by the operating system at run time (normally called plug and play). In plug-and-play systems, a device manager first performs a scan on different peripheral buses, such as Peripheral Component Interconnect (PCI) or Universal Serial Bus (USB), to detect installed devices, then searches for the appropriate drivers. As device management is a very OS-specific topic, these drivers are handled differently by each kind of kernel design, but in every case, the kernel has to provide the I/O to allow drivers to physically access their devices through some port or memory location. Important decisions have to be made when designing the device management system, as in some designs accesses may involve context switches, making the operation very CPU-intensive and easily causing a significant performance overhead. System calls In computing, a system call is how a process requests a service from an operating system's kernel that it does not normally have permission to run. System calls provide the interface between a process and the operating system. Most operations interacting with the system require permissions not available to a user-level process, e.g., I/O performed with a device present on the system, or any form of communication with other processes requires the use of system calls. A system call is a mechanism that is used by the application program to request a service from the operating system. They use a machine-code instruction that causes the processor to change mode. An example would be from supervisor mode to protected mode. This is where the operating system performs actions like accessing hardware devices or the memory management unit. Generally the operating system provides a library that sits between the operating system and normal user programs. Usually it is a C library such as Glibc or Windows API. The library handles the low-level details of passing information to the kernel and switching to supervisor mode. System calls include close, open, read, wait and write. To actually perform useful work, a process must be able to access the services provided by the kernel. This is implemented differently by each kernel, but most provide a C library or an API, which in turn invokes the related kernel functions. The method of invoking the kernel function varies from kernel to kernel. If memory isolation is in use, it is impossible for a user process to call the kernel directly, because that would be a violation of the processor's access control rules. A few possibilities are: Using a software-simulated interrupt. This method is available on most hardware, and is therefore very common. Using a call gate. A call gate is a special address stored by the kernel in a list in kernel memory at a location known to the processor. When the processor detects a call to that address, it instead redirects to the target location without causing an access violation. This requires hardware support, but the hardware for it is quite common. Using a special system call instruction. This technique requires special hardware support, which common architectures (notably, x86) may lack. System call instructions have been added to recent models of x86 processors, however, and some operating systems for PCs make use of them when available. Using a memory-based queue. An application that makes large numbers of requests but does not need to wait for the result of each may add details of requests to an area of memory that the kernel periodically scans to find requests. Kernel design decisions Protection An important consideration in the design of a kernel is the support it provides for protection from faults (fault tolerance) and from malicious behaviours (security). These two aspects are usually not clearly distinguished, and the adoption of this distinction in the kernel design leads to the rejection of a hierarchical structure for protection. The mechanisms or policies provided by the kernel can be classified according to several criteria, including: static (enforced at compile time) or dynamic (enforced at run time); pre-emptive or post-detection; according to the protection principles they satisfy (e.g., Denning); whether they are hardware supported or language based; whether they are more an open mechanism or a binding policy; and many more. Support for hierarchical protection domains is typically implemented using CPU modes. Many kernels provide implementation of "capabilities", i.e., objects that are provided to user code which allow limited access to an underlying object managed by the kernel. A common example is file handling: a file is a representation of information stored on a permanent storage device. The kernel may be able to perform many different operations, including read, write, delete or execute, but a user-level application may only be permitted to perform some of these operations (e.g., it may only be allowed to read the file). A common implementation of this is for the kernel to provide an object to the application (typically so called a "file handle") which the application may then invoke operations on, the validity of which the kernel checks at the time the operation is requested. Such a system may be extended to cover all objects that the kernel manages, and indeed to objects provided by other user applications. An efficient and simple way to provide hardware support of capabilities is to delegate to the memory management unit (MMU) the responsibility of checking access-rights for every memory access, a mechanism called capability-based addressing. Most commercial computer architectures lack such MMU support for capabilities. An alternative approach is to simulate capabilities using commonly supported hierarchical domains. In this approach, each protected object must reside in an address space that the application does not have access to; the kernel also maintains a list of capabilities in such memory. When an application needs to access an object protected by a capability, it performs a system call and the kernel then checks whether the application's capability grants it permission to perform the requested action, and if it is permitted performs the access for it (either directly, or by delegating the request to another user-level process). The performance cost of address space switching limits the practicality of this approach in systems with complex interactions between objects, but it is used in current operating systems for objects that are not accessed frequently or which are not expected to perform quickly. If the firmware does not support protection mechanisms, it is possible to simulate protection at a higher level, for example by simulating capabilities by manipulating page tables, but there are performance implications. Lack of hardware support may not be an issue, however, for systems that choose to use language-based protection. An important kernel design decision is the choice of the abstraction levels where the security mechanisms and policies should be implemented. Kernel security mechanisms play a critical role in supporting security at higher levels.<ref>J. Anderson, Computer Security Technology Planning Study , Air Force Elect. Systems Div., ESD-TR-73-51, October 1972.</ref> One approach is to use firmware and kernel support for fault tolerance (see above), and build the security policy for malicious behavior on top of that (adding features such as cryptography mechanisms where necessary), delegating some responsibility to the compiler. Approaches that delegate enforcement of security policy to the compiler and/or the application level are often called language-based security. The lack of many critical security mechanisms in current mainstream operating systems impedes the implementation of adequate security policies at the application abstraction level. In fact, a common misconception in computer security is that any security policy can be implemented in an application regardless of kernel support. Hardware- or language-based protection Typical computer systems today use hardware-enforced rules about what programs are allowed to access what data. The processor monitors the execution and stops a program that violates a rule, such as a user process that tries to write to kernel memory. In systems that lack support for capabilities, processes are isolated from each other by using separate address spaces. Calls from user processes into the kernel are regulated by requiring them to use one of the above-described system call methods. An alternative approach is to use language-based protection. In a language-based protection system, the kernel will only allow code to execute that has been produced by a trusted language compiler. The language may then be designed such that it is impossible for the programmer to instruct it to do something that will violate a security requirement. Advantages of this approach include: No need for separate address spaces. Switching between address spaces is a slow operation that causes a great deal of overhead, and a lot of optimization work is currently performed in order to prevent unnecessary switches in current operating systems. Switching is completely unnecessary in a language-based protection system, as all code can safely operate in the same address space. Flexibility. Any protection scheme that can be designed to be expressed via a programming language can be implemented using this method. Changes to the protection scheme (e.g. from a hierarchical system to a capability-based one) do not require new hardware. Disadvantages include: Longer application startup time. Applications must be verified when they are started to ensure they have been compiled by the correct compiler, or may need recompiling either from source code or from bytecode. Inflexible type systems. On traditional systems, applications frequently perform operations that are not type safe. Such operations cannot be permitted in a language-based protection system, which means that applications may need to be rewritten and may, in some cases, lose performance. Examples of systems with language-based protection include JX and Microsoft's Singularity. Process cooperation Edsger Dijkstra proved that from a logical point of view, atomic lock and unlock operations operating on binary semaphores are sufficient primitives to express any functionality of process cooperation. However this approach is generally held to be lacking in terms of safety and efficiency, whereas a message passing approach is more flexible. A number of other approaches (either lower- or higher-level) are available as well, with many modern kernels providing support for systems such as shared memory and remote procedure calls. I/O device management The idea of a kernel where I/O devices are handled uniformly with other processes, as parallel co-operating processes, was first proposed and implemented by Brinch Hansen (although similar ideas were suggested in 1967). In Hansen's description of this, the "common" processes are called internal processes, while the I/O devices are called external processes. Similar to physical memory, allowing applications direct access to controller ports and registers can cause the controller to malfunction, or system to crash. With this, depending on the complexity of the device, some devices can get surprisingly complex to program, and use several different controllers. Because of this, providing a more abstract interface to manage the device is important. This interface is normally done by a device driver or hardware abstraction layer. Frequently, applications will require access to these devices. The kernel must maintain the list of these devices by querying the system for them in some way. This can be done through the BIOS, or through one of the various system buses (such as PCI/PCIE, or USB). Using an example of a video driver, when an application requests an operation on a device, such as displaying a character, the kernel needs to send this request to the current active video driver. The video driver, in turn, needs to carry out this request. This is an example of inter-process communication (IPC). Kernel-wide design approaches Naturally, the above listed tasks and features can be provided in many ways that differ from each other in design and implementation. The principle of separation of mechanism and policy is the substantial difference between the philosophy of micro and monolithic kernels.Levin 75 Here a mechanism is the support that allows the implementation of many different policies, while a policy is a particular "mode of operation". Example: Mechanism: User login attempts are routed to an authorization server Policy: Authorization server requires a password which is verified against stored passwords in a database Because the mechanism and policy are separated, the policy can be easily changed to e.g. require the use of a security token. In minimal microkernel just some very basic policies are included, and its mechanisms allows what is running on top of the kernel (the remaining part of the operating system and the other applications) to decide which policies to adopt (as memory management, high level process scheduling, file system management, etc.). A monolithic kernel instead tends to include many policies, therefore restricting the rest of the system to rely on them. Per Brinch Hansen presented arguments in favour of separation of mechanism and policy. The failure to properly fulfill this separation is one of the major causes of the lack of substantial innovation in existing operating systems, a problem common in computer architecture.Jürgen Nehmer, "The Immortality of Operating Systems, or: Is Research in Operating Systems still Justified?", Lecture Notes In Computer Science; Vol. 563. Proceedings of the International Workshop on Operating Systems of the 90s and Beyond. pp. 77–83 (1991) quote: "The past 25 years have shown that research on operating system architecture had a minor effect on existing main stream systems." The monolithic design is induced by the "kernel mode"/"user mode" architectural approach to protection (technically called hierarchical protection domains), which is common in conventional commercial systems; in fact, every module needing protection is therefore preferably included into the kernel. This link between monolithic design and "privileged mode" can be reconducted to the key issue of mechanism-policy separation; in fact the "privileged mode" architectural approach melds together the protection mechanism with the security policies, while the major alternative architectural approach, capability-based addressing, clearly distinguishes between the two, leading naturally to a microkernel design (see Separation of protection and security). While monolithic kernels execute all of their code in the same address space (kernel space), microkernels try to run most of their services in user space, aiming to improve maintainability and modularity of the codebase. Most kernels do not fit exactly into one of these categories, but are rather found in between these two designs. These are called hybrid kernels. More exotic designs such as nanokernels and exokernels are available, but are seldom used for production systems. The Xen hypervisor, for example, is an exokernel. Monolithic kernels In a monolithic kernel, all OS services run along with the main kernel thread, thus also residing in the same memory area. This approach provides rich and powerful hardware access. Some developers, such as UNIX developer Ken Thompson, maintain that it is "easier to implement a monolithic kernel" than microkernels. The main disadvantages of monolithic kernels are the dependencies between system components a bug in a device driver might crash the entire system and the fact that large kernels can become very difficult to maintain. Monolithic kernels, which have traditionally been used by Unix-like operating systems, contain all the operating system core functions and the device drivers. This is the traditional design of UNIX systems. A monolithic kernel is one single program that contains all of the code necessary to perform every kernel-related task. Every part which is to be accessed by most programs which cannot be put in a library is in the kernel space: Device drivers, scheduler, memory handling, file systems, and network stacks. Many system calls are provided to applications, to allow them to access all those services. A monolithic kernel, while initially loaded with subsystems that may not be needed, can be tuned to a point where it is as fast as or faster than the one that was specifically designed for the hardware, although more relevant in a general sense. Modern monolithic kernels, such as those of Linux (one of the kernels of the GNU operating system) and FreeBSD kernel, both of which fall into the category of Unix-like operating systems, feature the ability to load modules at runtime, thereby allowing easy extension of the kernel's capabilities as required, while helping to minimize the amount of code running in kernel space. In the monolithic kernel, some advantages hinge on these points: Since there is less software involved it is faster. As it is one single piece of software it should be smaller both in source and compiled forms. Less code generally means fewer bugs which can translate to fewer security problems. Most work in the monolithic kernel is done via system calls. These are interfaces, usually kept in a tabular structure, that access some subsystem within the kernel such as disk operations. Essentially calls are made within programs and a checked copy of the request is passed through the system call. Hence, not far to travel at all. The monolithic Linux kernel can be made extremely small not only because of its ability to dynamically load modules but also because of its ease of customization. In fact, there are some versions that are small enough to fit together with a large number of utilities and other programs on a single floppy disk and still provide a fully functional operating system (one of the most popular of which is muLinux). This ability to miniaturize its kernel has also led to a rapid growth in the use of Linux in embedded systems. These types of kernels consist of the core functions of the operating system and the device drivers with the ability to load modules at runtime. They provide rich and powerful abstractions of the underlying hardware. They provide a small set of simple hardware abstractions and use applications called servers to provide more functionality. This particular approach defines a high-level virtual interface over the hardware, with a set of system calls to implement operating system services such as process management, concurrency and memory management in several modules that run in supervisor mode. This design has several flaws and limitations: Coding in kernel can be challenging, in part because one cannot use common libraries (like a full-featured libc), and because one needs to use a source-level debugger like gdb. Rebooting the computer is often required. This is not just a problem of convenience to the developers. When debugging is harder, and as difficulties become stronger, it becomes more likely that code will be "buggier". Bugs in one part of the kernel have strong side effects; since every function in the kernel has all the privileges, a bug in one function can corrupt data structure of another, totally unrelated part of the kernel, or of any running program. Kernels often become very large and difficult to maintain. Even if the modules servicing these operations are separate from the whole, the code integration is tight and difficult to do correctly. Since the modules run in the same address space, a bug can bring down the entire system. Monolithic kernels are not portable; therefore, they must be rewritten for each new architecture that the operating system is to be used on. Examples of monolithic kernels are AIX kernel, HP-UX kernel and Solaris kernel. Microkernels Microkernel (also abbreviated μK or uK) is the term describing an approach to operating system design by which the functionality of the system is moved out of the traditional "kernel", into a set of "servers" that communicate through a "minimal" kernel, leaving as little as possible in "system space" and as much as possible in "user space". A microkernel that is designed for a specific platform or device is only ever going to have what it needs to operate. The microkernel approach consists of defining a simple abstraction over the hardware, with a set of primitives or system calls to implement minimal OS services such as memory management, multitasking, and inter-process communication. Other services, including those normally provided by the kernel, such as networking, are implemented in user-space programs, referred to as servers. Microkernels are easier to maintain than monolithic kernels, but the large number of system calls and context switches might slow down the system because they typically generate more overhead than plain function calls. Only parts which really require being in a privileged mode are in kernel space: IPC (Inter-Process Communication), basic scheduler, or scheduling primitives, basic memory handling, basic I/O primitives. Many critical parts are now running in user space: The complete scheduler, memory handling, file systems, and network stacks. Micro kernels were invented as a reaction to traditional "monolithic" kernel design, whereby all system functionality was put in a one static program running in a special "system" mode of the processor. In the microkernel, only the most fundamental of tasks are performed such as being able to access some (not necessarily all) of the hardware, manage memory and coordinate message passing between the processes. Some systems that use micro kernels are QNX and the HURD. In the case of QNX and Hurd user sessions can be entire snapshots of the system itself or views as it is referred to. The very essence of the microkernel architecture illustrates some of its advantages: Easier to maintain Patches can be tested in a separate instance, and then swapped in to take over a production instance. Rapid development time and new software can be tested without having to reboot the kernel. More persistence in general, if one instance goes haywire, it is often possible to substitute it with an operational mirror. Most microkernels use a message passing system to handle requests from one server to another. The message passing system generally operates on a port basis with the microkernel. As an example, if a request for more memory is sent, a port is opened with the microkernel and the request sent through. Once within the microkernel, the steps are similar to system calls. The rationale was that it would bring modularity in the system architecture, which would entail a cleaner system, easier to debug or dynamically modify, customizable to users' needs, and more performing. They are part of the operating systems like GNU Hurd, MINIX, MkLinux, QNX and Redox OS. Although microkernels are very small by themselves, in combination with all their required auxiliary code they are, in fact, often larger than monolithic kernels. Advocates of monolithic kernels also point out that the two-tiered structure of microkernel systems, in which most of the operating system does not interact directly with the hardware, creates a not-insignificant cost in terms of system efficiency. These types of kernels normally provide only the minimal services such as defining memory address spaces, inter-process communication (IPC) and the process management. The other functions such as running the hardware processes are not handled directly by microkernels. Proponents of micro kernels point out those monolithic kernels have the disadvantage that an error in the kernel can cause the entire system to crash. However, with a microkernel, if a kernel process crashes, it is still possible to prevent a crash of the system as a whole by merely restarting the service that caused the error. Other services provided by the kernel such as networking are implemented in user-space programs referred to as servers. Servers allow the operating system to be modified by simply starting and stopping programs. For a machine without networking support, for instance, the networking server is not started. The task of moving in and out of the kernel to move data between the various applications and servers creates overhead which is detrimental to the efficiency of micro kernels in comparison with monolithic kernels. Disadvantages in the microkernel exist however. Some are: Larger running memory footprint More software for interfacing is required, there is a potential for performance loss. Messaging bugs can be harder to fix due to the longer trip they have to take versus the one off copy in a monolithic kernel. Process management in general can be very complicated. The disadvantages for microkernels are extremely context-based. As an example, they work well for small single-purpose (and critical) systems because if not many processes need to run, then the complications of process management are effectively mitigated. A microkernel allows the implementation of the remaining part of the operating system as a normal application program written in a high-level language, and the use of different operating systems on top of the same unchanged kernel. It is also possible to dynamically switch among operating systems and to have more than one active simultaneously. Monolithic kernels vs. microkernels As the computer kernel grows, so grows the size and vulnerability of its trusted computing base; and, besides reducing security, there is the problem of enlarging the memory footprint. This is mitigated to some degree by perfecting the virtual memory system, but not all computer architectures have virtual memory support. To reduce the kernel's footprint, extensive editing has to be performed to carefully remove unneeded code, which can be very difficult with non-obvious interdependencies between parts of a kernel with millions of lines of code. By the early 1990s, due to the various shortcomings of monolithic kernels versus microkernels, monolithic kernels were considered obsolete by virtually all operating system researchers. As a result, the design of Linux as a monolithic kernel rather than a microkernel was the topic of a famous debate between Linus Torvalds and Andrew Tanenbaum. There is merit on both sides of the argument presented in the Tanenbaum–Torvalds debate. Performance Monolithic kernels are designed to have all of their code in the same address space (kernel space), which some developers argue is necessary to increase the performance of the system. Some developers also maintain that monolithic systems are extremely efficient if well written. The monolithic model tends to be more efficient through the use of shared kernel memory, rather than the slower IPC system of microkernel designs, which is typically based on message passing. The performance of microkernels was poor in both the 1980s and early 1990s.Härtig 97 However, studies that empirically measured the performance of these microkernels did not analyze the reasons of such inefficiency. The explanations of this data were left to "folklore", with the assumption that they were due to the increased frequency of switches from "kernel-mode" to "user-mode", to the increased frequency of inter-process communication and to the increased frequency of context switches. In fact, as guessed in 1995, the reasons for the poor performance of microkernels might as well have been: (1) an actual inefficiency of the whole microkernel approach, (2) the particular concepts implemented in those microkernels, and (3) the particular implementation of those concepts. Therefore it remained to be studied if the solution to build an efficient microkernel was, unlike previous attempts, to apply the correct construction techniques. On the other end, the hierarchical protection domains architecture that leads to the design of a monolithic kernel has a significant performance drawback each time there's an interaction between different levels of protection (i.e., when a process has to manipulate a data structure both in "user mode" and "supervisor mode"), since this requires message copying by value. Hybrid (or modular) kernels Hybrid kernels are used in most commercial operating systems such as Microsoft Windows NT 3.1, NT 3.5, NT 3.51, NT 4.0, 2000, XP, Vista, 7, 8, 8.1 and 10. Apple Inc's own macOS uses a hybrid kernel called XNU which is based upon code from OSF/1's Mach kernel (OSFMK 7.3) and FreeBSD's monolithic kernel. They are similar to micro kernels, except they include some additional code in kernel-space to increase performance. These kernels represent a compromise that was implemented by some developers to accommodate the major advantages of both monolithic and micro kernels. These types of kernels are extensions of micro kernels with some properties of monolithic kernels. Unlike monolithic kernels, these types of kernels are unable to load modules at runtime on their own. Hybrid kernels are micro kernels that have some "non-essential" code in kernel-space in order for the code to run more quickly than it would were it to be in user-space. Hybrid kernels are a compromise between the monolithic and microkernel designs. This implies running some services (such as the network stack or the filesystem) in kernel space to reduce the performance overhead of a traditional microkernel, but still running kernel code (such as device drivers) as servers in user space. Many traditionally monolithic kernels are now at least adding (or else using) the module capability. The most well known of these kernels is the Linux kernel. The modular kernel essentially can have parts of it that are built into the core kernel binary or binaries that load into memory on demand. It is important to note that a code tainted module has the potential to destabilize a running kernel. Many people become confused on this point when discussing micro kernels. It is possible to write a driver for a microkernel in a completely separate memory space and test it before "going" live. When a kernel module is loaded, it accesses the monolithic portion's memory space by adding to it what it needs, therefore, opening the doorway to possible pollution. A few advantages to the modular (or) Hybrid kernel are: Faster development time for drivers that can operate from within modules. No reboot required for testing (provided the kernel is not destabilized). On demand capability versus spending time recompiling a whole kernel for things like new drivers or subsystems. Faster integration of third party technology (related to development but pertinent unto itself nonetheless). Modules, generally, communicate with the kernel using a module interface of some sort. The interface is generalized (although particular to a given operating system) so it is not always possible to use modules. Often the device drivers may need more flexibility than the module interface affords. Essentially, it is two system calls and often the safety checks that only have to be done once in the monolithic kernel now may be done twice. Some of the disadvantages of the modular approach are: With more interfaces to pass through, the possibility of increased bugs exists (which implies more security holes). Maintaining modules can be confusing for some administrators when dealing with problems like symbol differences. Nanokernels A nanokernel delegates virtually all services including even the most basic ones like interrupt controllers or the timer to device drivers to make the kernel memory requirement even smaller than a traditional microkernel. Exokernels Exokernels are a still-experimental approach to operating system design. They differ from other types of kernels in limiting their functionality to the protection and multiplexing of the raw hardware, providing no hardware abstractions on top of which to develop applications. This separation of hardware protection from hardware management enables application developers to determine how to make the most efficient use of the available hardware for each specific program. Exokernels in themselves are extremely small. However, they are accompanied by library operating systems (see also unikernel), providing application developers with the functionalities of a conventional operating system. This comes down to every user writing his own rest-of-the kernel from near scratch, which is a very-risky, complex and quite a daunting assignment - particularly in a time-constrained production-oriented environment, which is why exokernels have never caught on. A major advantage of exokernel-based systems is that they can incorporate multiple library operating systems, each exporting a different API, for example one for high level UI development and one for real-time control. History of kernel development Early operating system kernels Strictly speaking, an operating system (and thus, a kernel) is not required to run a computer. Programs can be directly loaded and executed on the "bare metal" machine, provided that the authors of those programs are willing to work without any hardware abstraction or operating system support. Most early computers operated this way during the 1950s and early 1960s, which were reset and reloaded between the execution of different programs. Eventually, small ancillary programs such as program loaders and debuggers were left in memory between runs, or loaded from ROM. As these were developed, they formed the basis of what became early operating system kernels. The "bare metal" approach is still used today on some video game consoles and embedded systems, but in general, newer computers use modern operating systems and kernels. In 1969, the RC 4000 Multiprogramming System introduced the system design philosophy of a small nucleus "upon which operating systems for different purposes could be built in an orderly manner", what would be called the microkernel approach. Time-sharing operating systems In the decade preceding Unix, computers had grown enormously in power to the point where computer operators were looking for new ways to get people to use their spare time on their machines. One of the major developments during this era was time-sharing, whereby a number of users would get small slices of computer time, at a rate at which it appeared they were each connected to their own, slower, machine. The development of time-sharing systems led to a number of problems. One was that users, particularly at universities where the systems were being developed, seemed to want to hack the system to get more CPU time. For this reason, security and access control became a major focus of the Multics project in 1965. Another ongoing issue was properly handling computing resources: users spent most of their time staring at the terminal and thinking about what to input instead of actually using the resources of the computer, and a time-sharing system should give the CPU time to an active user during these periods. Finally, the systems typically offered a memory hierarchy several layers deep, and partitioning this expensive resource led to major developments in virtual memory systems. Amiga The Commodore Amiga was released in 1985, and was among the first and certainly most successful home computers to feature an advanced kernel architecture. The AmigaOS kernel's executive component, exec.library, uses a microkernel message-passing design, but there are other kernel components, like graphics.library, that have direct access to the hardware. There is no memory protection, and the kernel is almost always running in user mode. Only special actions are executed in kernel mode, and user-mode applications can ask the operating system to execute their code in kernel mode. Unix During the design phase of Unix, programmers decided to model every high-level device as a file, because they believed the purpose of computation was data transformation. For instance, printers were represented as a "file" at a known location when data was copied to the file, it printed out. Other systems, to provide a similar functionality, tended to virtualize devices at a lower level that is, both devices and files would be instances of some lower level concept. Virtualizing the system at the file level allowed users to manipulate the entire system using their existing file management utilities and concepts, dramatically simplifying operation. As an extension of the same paradigm, Unix allows programmers to manipulate files using a series of small programs, using the concept of pipes, which allowed users to complete operations in stages, feeding a file through a chain of single-purpose tools. Although the end result was the same, using smaller programs in this way dramatically increased flexibility as well as ease of development and use, allowing the user to modify their workflow by adding or removing a program from the chain. In the Unix model, the operating system consists of two parts: first, the huge collection of utility programs that drive most operations; second, the kernel that runs the programs. Under Unix, from a programming standpoint, the distinction between the two is fairly thin; the kernel is a program, running in supervisor mode, that acts as a program loader and supervisor for the small utility programs making up the rest of the system, and to provide locking and I/O services for these programs; beyond that, the kernel didn't intervene at all in user space. Over the years the computing model changed, and Unix's treatment of everything as a file or byte stream no longer was as universally applicable as it was before. Although a terminal could be treated as a file or a byte stream, which is printed to or read from, the same did not seem to be true for a graphical user interface. Networking posed another problem. Even if network communication can be compared to file access, the low-level packet-oriented architecture dealt with discrete chunks of data and not with whole files. As the capability of computers grew, Unix became increasingly cluttered with code. It is also because the modularity of the Unix kernel is extensively scalable. While kernels might have had 100,000 lines of code in the seventies and eighties, kernels like Linux, of modern Unix successors like GNU, have more than 13 million lines. Modern Unix-derivatives are generally based on module-loading monolithic kernels. Examples of this are the Linux kernel in the many distributions of GNU, IBM AIX, as well as the Berkeley Software Distribution variant kernels such as FreeBSD, DragonflyBSD, OpenBSD, NetBSD, and macOS. Apart from these alternatives, amateur developers maintain an active operating system development community, populated by self-written hobby kernels which mostly end up sharing many features with Linux, FreeBSD, DragonflyBSD, OpenBSD or NetBSD kernels and/or being compatible with them. Mac OS Apple first launched its classic Mac OS in 1984, bundled with its Macintosh personal computer. Apple moved to a nanokernel design in Mac OS 8.6. Against this, the modern macOS (originally named Mac OS X) is based on Darwin, which uses a hybrid kernel called XNU, which was created by combining the 4.3BSD kernel and the Mach kernel. Microsoft Windows Microsoft Windows was first released in 1985 as an add-on to MS-DOS. Because of its dependence on another operating system, initial releases of Windows, prior to Windows 95, were considered an operating environment (not to be confused with an operating system). This product line continued to evolve through the 1980s and 1990s, with the Windows 9x series adding 32-bit addressing and pre-emptive multitasking; but ended with the release of Windows Me in 2000. Microsoft also developed Windows NT, an operating system with a very similar interface, but intended for high-end and business users. This line started with the release of Windows NT 3.1 in 1993, and was introduced to general users with the release of Windows XP in October 2001—replacing Windows 9x with a completely different, much more sophisticated operating system. This is the line that continues with Windows 11. The architecture of Windows NT's kernel is considered a hybrid kernel because the kernel itself contains tasks such as the Window Manager and the IPC Managers, with a client/server layered subsystem model. It was designed as a modified microkernel, as the Windows NT kernel was influenced by the Mach microkernel but does not meet all of the criteria of a pure microkernel. IBM Supervisor Supervisory program or supervisor is a computer program, usually part of an operating system, that controls the execution of other routines and regulates work scheduling, input/output operations, error actions, and similar functions and regulates the flow of work in a data processing system. Historically, this term was essentially associated with IBM's line of mainframe operating systems starting with OS/360. In other operating systems, the supervisor is generally called the kernel. In the 1970s, IBM further abstracted the supervisor state from the hardware, resulting in a hypervisor that enabled full virtualization, i.e. the capacity to run multiple operating systems on the same machine totally independently from each other. Hence the first such system was called Virtual Machine or VM. Development of microkernels Although Mach, developed by Richard Rashid at Carnegie Mellon University, is the best-known general-purpose microkernel, other microkernels have been developed with more specific aims. The L4 microkernel family (mainly the L3 and the L4 kernel) was created to demonstrate that microkernels are not necessarily slow. Newer implementations such as Fiasco and Pistachio are able to run Linux next to other L4 processes in separate address spaces. Additionally, QNX is a microkernel which is principally used in embedded systems, and the open-source software MINIX, while originally created for educational purposes, is now focused on being a highly reliable and self-healing microkernel OS. See also Comparison of operating system kernels Inter-process communication Operating system Virtual memory Notes References Sources included in book: Hermann Härtig, Michael Hohmuth, Jochen Liedtke, Sebastian Schönberg, Jean Wolter The performance of μ-kernel-based systems , ACM SIGOPS Operating Systems Review, v.31 n.5, p. 66–77, Dec. 1997 Houdek, M. E., Soltis, F. G., and Hoffman, R. L. 1981. IBM System/38 support for capability-based addressing. In Proceedings of the 8th ACM International Symposium on Computer Architecture. ACM/IEEE, pp. 341–348. Intel Corporation (2002) The IA-32 Architecture Software Developer's Manual, Volume 1: Basic Architecture Liedtke, Jochen. On µ-Kernel Construction, Proc. 15th ACM Symposium on Operating System Principles (SOSP), December 1995 , Further reading Andrew Tanenbaum, Operating Systems – Design and Implementation (Third edition); Andrew Tanenbaum, Modern Operating Systems (Second edition); Daniel P. Bovet, Marco Cesati, The Linux Kernel; David A. Peterson, Nitin Indurkhya, Patterson, Computer Organization and Design, Morgan Koffman (); B.S. Chalk, Computer Organisation and Architecture'', Macmillan P.(). External links Detailed comparison between most popular operating system kernels Operating systems

Operating System (OS)

Apple ProDOS ProDOS is the name of two similar operating systems for the Apple II series of personal computers. The original ProDOS, renamed ProDOS 8 in version 1.2, is the last official operating system usable by all 8-bit Apple II series computers, and was distributed from 1983 to 1993. The other, ProDOS 16, was a stop-gap solution for the 16-bit Apple II that was replaced by GS/OS within two years. ProDOS was marketed by Apple as meaning Professional Disk Operating System, and became the most popular operating system for the Apple II series of computers 10 months after its release in January 1983. Background ProDOS was released to address shortcomings in the earlier Apple operating system (called simply DOS), which was beginning to show its age. Apple DOS only has built-in support for 5.25" floppy disks and requires patches to use peripheral devices such as hard disk drives and non-Disk-II floppy disk drives, including 3.5" floppy drives. ProDOS adds a standard method of accessing ROM-based drivers on expansion cards for disk devices, expands the maximum volume size from about 400 kilobytes to 32 megabytes, introduces support for hierarchical subdirectories (a vital feature for organizing a hard disk's storage space), and supports RAM disks on machines with 128kB or more of memory. ProDOS addresses problems with handling hardware interrupts, and includes a well-defined and documented programming and expansion interface, which Apple DOS had always lacked. Although ProDOS also includes support for a real-time clock (RTC), this support went largely unused until the release of the Apple II, the first in the Apple II series to include an RTC on board. Third-party clocks were available for the II Plus, IIe, and IIc, however. ProDOS, unlike earlier Apple DOS versions, has its developmental roots in SOS, the operating system for the ill-fated Apple III computer released in 1980. Pre-release documentation for ProDOS (including early editions of Beneath Apple ProDOS) documented SOS error codes, notably one for switched disks, that ProDOS itself could never generate. Its disk format and programming interface are completely different from those of Apple DOS, and ProDOS cannot read or write DOS 3.3 disks except by means of a conversion utility; while the low-level track-and-sector format of DOS 3.3 disks was retained for 5.25-inch disks, the high-level arrangement of files and directories is completely different. For this reason, most machine-language programs that run under Apple DOS will not work under ProDOS. However, most BASIC programs work, though they sometimes require minor changes. A third-party program called DOS.MASTER enables users to have multiple virtual DOS 3.3 partitions on a larger ProDOS volume. With the release of ProDOS came the end of support for Integer BASIC and the original Apple II model, which had long since been effectively supplanted by Applesoft BASIC and the Apple II Plus. Whereas DOS 3.3 always loads built-in support for BASIC programming, under ProDOS this job is given to a separate system program called , which one launches to run and write Applesoft BASIC programs. BASIC itself continued to be built into the Apple ROMs; is merely a command interpreter enhancement that allows BASIC programs to access ProDOS by means of the same "Control-D" text output they had used under DOS 3.3. alone requires about as much memory as the whole of DOS 3.3. Since the ProDOS kernel itself is stowed away in the "Language Card" RAM, the usable amount of RAM for BASIC programmers remains the same under ProDOS as it had been under DOS 3.3. Despite ProDOS's many advantages, many users and programmers resisted it for a time because of their investment in learning the ins and outs of Apple DOS and in Apple-DOS-based software and data formats. A contributing reason was that ProDOS allows only 15 characters in a filename compared to Apple DOS's 30. But Apple's integrated software package AppleWorks, released in 1984, proved a compelling reason to switch, and by the end of 1985 few new software products were being released for the older operating system. Apple IIs continued to be able to boot the older DOS (even the Apple IIGS can boot the older DOS floppies) but as 3.5" floppies and hard disks became more prevalent, most users spent the bulk of their time in ProDOS. The Apple IIe, also released in 1983, was the first Apple II computer to have 64kB of memory built in. For a while, Apple shipped both DOS 3.3 and ProDOS with new computers. The original ProDOS was renamed ProDOS 8 when ProDOS 16 was released to support the 16-bit Apple II computer, although ProDOS 16 (which was 8-bit at its core) was soon replaced by GS/OS. Requirements All editions of ProDOS require an Apple II series computer or compatible. ProDOS 8 requires 64kB of memory to run. The original ProDOS (8) 1.0 through 1.0.2 requires only 48kB for the kernel, but nearly all programs, including the needed to use Applesoft BASIC, require 64kB, making a 48kB system useless for ProDOS as a practical matter, and support for 48kB machines was removed in version 1.1. ProDOS 8 version 2.x requires a 65C02 or later (65802, 65816) CPU. ProDOS 8 2.x runs in 64kB, but the utility programs on the system disk require 128kB. Systems with a 6502 CPU instead of a 65C02 must use ProDOS 8 versions prior to version 2.0. ProDOS 16 requires an Apple IIGS. Unlicensed Apple II clones With the release of ProDOS version 1.01 and higher, a check was added to see if it was running on an official Apple-manufactured computer. If the word "Apple" is found in the computer's ROM firmware, ProDOS will load up as normal. If anything else is found (e.g. "Golden", "Franklin", "Elite") ProDOS refuses to run, locking up at the boot splash screen. This measure was taken by Apple Computer to discourage use of unlicensed Apple II clones. It is still possible to run newer versions of ProDOS on clones; however, users have to apply a small byte patch to every successive version of ProDOS. Some users go as far as replacing their physical ROM chip(s) with an illegal copied version of Apple's own ROM; or, failing that, a custom patched ROM with "Apple" added in the name. Disk support ProDOS 8 natively supports Disk II-compatible floppy drives, a RAM drive of approximately 59kB on computers having 128K or more RAM, and block devices whose controllers support the Pascal firmware protocol, a standardized method of accepting block reads and writes originally introduced for use with the UCSD p-System. This latter category includes 3.5" disk and hard drives. Custom block device drivers can be hooked into the OS as well. File system ProDOS uses the same file system as the earlier Apple SOS for the Apple III. The SOS/ProDOS file system is native to Apple SOS, ProDOS 8, ProDOS 16, and GS/OS. Some classic Mac OS versions also come with a file system translator to handle this file system. A volume is allocated in 512-byte blocks. (5.25" floppy disks are still formatted using 256-byte sectors, as this is the format required by the controller ROM to boot the disk. ProDOS simply treats pairs of 256-byte sectors as a single block on such drives.) A volume can have a capacity of up to 32 megabytes, and each file can be up to 16 megabytes. Each volume (floppy disk or hard drive partition) has a "volume name", a filename which is used as the base directory name; having two volumes with the same volume name can result in conflicts. If necessary, ProDOS searches all available drives to find a named volume. Subdirectories are supported, and the concept of a "prefix" (working directory or current path) was provided to make working with subdirectories easier. File, directory, and volume names can be 1 to 15 characters, starting with a letter, then containing more letters, digits or periods. Each file entry also contains the 16-bit (2-byte) pointer to the block containing the beginning of the file (or its block index); a 16-bit block count; a 24-bit (3-byte) file size; an 8-bit (1-byte) filetype; a 16-bit auxiliary type (the meaning of which depends upon the filetype); creation and modification timestamps; and data related to how the file is stored on the volume. Sparse files are supported, but files are never "sparsified" by removing zero-filled blocks. The volume header contains similar information as relevant to volumes. Directories (including the root directory) are sequentially indexed, with each block starting with the address of the previous block (or zero if none) and the subsequent block (or zero if none). The root directory on most disks is initialized to 4 blocks, allowing 51 entries (excluding the volume header). It never changes in size, except by manual intervention with special tools. Subdirectories begin at one block, and grow automatically as needed. Normal files are progressively indexed. Single-block files (under 513 bytes) have no index block; the directory entry points directly to the block of file data. Files with between 2 and 256 blocks (513 bytes to 128 kB) of data have a single index block, to which the directory entry points, which contains a list of up to 256 data block addresses. Larger files have a master index block containing a list of up to 256 index block addresses. When the Apple IIgs was introduced, a new storage format was introduced for files with two forks, as was typical for IIgs system and program files; the directory entry points to an informational block that tells the computer the storage format of the two forks. These files cannot be read or written natively by ProDOS 8, though the volume itself remains compatible. The volume has a bitmap of used blocks. Other than this, there is no central file allocation table. A ProDOS 8 volume formatted by Apple's tools has a boot sector that supports booting both ProDOS and SOS depending on what computer it is booted on. Block 0 is the Apple II boot block and block 1 boots SOS. This allows a disk to be used to boot on either Apple II or Apple III computers by putting both operating system kernels in the top directory: the Apple II boot sector looks for the file and the Apple III boot sector looks for the file . Third-party formatting utilities often did not provide the SOS boot block, and some would even mark block 1 available for user data. ProDOS has no kernel support for other file systems. If necessary, a conversion utility on the main system disk is used to transfer files individually between ProDOS and older Apple DOS 3.3 disks. Because they use a different low-level disk format than DOS 3.3 and ProDOS, transferring data from DOS 3.2 disks to ProDOS is a two-step process using a DOS 3.3 disk as an intermediary (utilizing the DOS 3.3 utility MUFFIN or similar). References Notes Don Worth and Pieter Lechner. Beneath Apple ProDOS. Quality Software, Chatsworth, California, 1984. External links Apple II History: DOS 3.3, ProDOS & Beyond Apple II Information Reference - Apple2.info - ProDOS 8 Technical Reference Manual, wiki formatted, with FAQs, compatibility guides, etc. ProDOS 8 Technical Reference Manual - HTML formatted Apple II System Disk 4.0.2 - Apple II System Disk 4.0.2, with ProDOS 8 2.0.3 and the system utilities, as an 800K DiskCopy format image Apple Operating Systems - DOS, ProDOS 8, GS/OS, Basic.System ProDOS ProDOS Disk operating systems Discontinued operating systems 1983 software

Operating System (OS)

Edos Edos is a discontinued operating system based upon IBM's original mainframe DOS (not to be confused with the unrelated and better known MS-DOS for the IBM PC). The name stood for extended (or enhanced) disk operating system. In 1970, IBM announced the IBM/370 product line along with new peripherals, software products, and operating systems, including DOS/VS that supplanted DOS. Although IBM was rightly focused on their new products, the computing world was dominated by the IBM/360 line, which left a lot of users nervous about their investment. Although there were a couple of projects emulating the IBM/370 on the IBM/360 (e.g., CFS, Inc.), a couple of companies took a different approach, extending the then-current (and limited) DOS. The Computer Software Company (TCSC) took the latter approach. Starting in 1972, they developed Edos, Extended Disk Operating System. They extended the number of fixed program space partitions from 3 to 6, added support for new hardware, and included features that IBM had offered separately. The first version of Edos was released in 1972, in response to the announcement by IBM that DOS Release 26 was the last DOS release to be supported on the System 360, and future DOS Releases would support System 370 machines only. They also made available other third party enhancements such as a spooler and DOCS, from CFS, Inc. Edos/VS and Edos/VSE TCSC enhanced EDOS to become EDOS/VS, which was announced in 1977 and delivered it to beta test sites in 1978. In May 1977, TCSC announced it would release Edos/VS in response to IBM's release of DOS/VS Release 34 and Advanced Functions-DOS/VS. Edos/VS was based on IBM's DOS/VS Release 34, and provided equivalent functionality to IBM's Advanced Functions-DOS/VS product. Unlike IBM's offerings, Edos/VS would run on System 360 machines and System 370 machines lacking virtual storage hardware (non-VS machines), whereas IBM's offerings only supported the latest System 370 models with VS hardware included. TCSC identified the parts of IBM's DOS/VS Release 34 operating system which relied upon System/370-only machine instructions and rewrote them to use instructions supported by the System/360. TCSC was legally able to reuse IBM's DOS/VS Release 34 code, since IBM had (intentionally) published the code without a copyright notice, which made it public domain under US copyright law at the time. In 1981, NCSC announced plans to release an Edos/VSE 2.0, based on IBM DOS/VSE Release 35, suitable for IBM 4300 machines. TCSC corporate history TCSC was founded by Jerry Enfield and Tom Steel, responsible for development and marketing, respectively. Company headquarters were in Richmond, Virginia. TCSC expanded into Canada, Australia, and Europe. In 1980, the company was acquired by Nixdorf and became NCSC. Other products of TCSC included the Extended Console (Econ) system, which enabled display of the system console using a CRT terminal such as an IBM 3270. Econ was available for IBM's DOS and DOS/VS and TCSC's Edos and Edos/VS operating systems. TCSC licensed DATACOM/DB from Applied Data Research (ADR) to run under its EDos and EDos/VS operating systems. When in 1980 Nixdorf bought TCSC, Nixdorf sought to continue the licensing arrangement; ADR and NCSC went to court in a dispute over whether the licensing arrangement was terminated by the acquisition. ADR and Nixdorf settled out of court in 1981, with an agreement that Nixdorf could continue to resell ADR's products. Add-on products for Edos In 1973, TCSC released a remote job entry (RJE) option for Edos. In 1975, TCSC released a tape management system for Edos known as TMS. In 1983, NCSC announced a Unix compatibility subsystem for IBM mainframes running IBM's DOS/VS(E) and Nixdorf's Edos/VS and Edos/VSE operating systems, known as Programmer Work Station/VSE-Advanced Functions, or PWS/VSE-AF for short. PWS/VSE-AF was based on the Coherent Unix clone developed by Mark Williams Company. References Disk operating systems IBM mainframe operating systems 1972 software

Operating System (OS)

System 1 The Macintosh "System 1" is the first version of Apple Macintosh operating system and the beginning of the classic Mac OS series. It was developed for the Motorola 68000 microprocessor. System 1 was released on January 24, 1984, along with the Macintosh 128K, the first in the Macintosh family of personal computers. It received one update, "System 1.1" on December 29, 1984, before being succeeded by System 2. Features This operating system introduced many features that would appear for years to come, some that still exist in the current macOS, and a few that exist in other graphical operating systems such as Microsoft Windows. The features of the operating system included the Finder and menu bar. In addition to this, it popularized the graphical user interface and desktop metaphor, which was used under license from Xerox PARC. Due to the limited amount of random-access memory and the lack of an internal hard disk in the original Macintosh, there was no multitasking with multiple applications, although there were desktop accessories that could run while another application was loaded. Also, items in the Trash were permanently deleted when the computer was shut down or an application was loaded (quitting the Finder). System 1's total size is about 216 KB and contained six files: System (which includes the desk accessories), Finder, Clipboard, an Imagewriter printer driver, Scrapbook, and Note Pad. A separate diskette included "A Guided Tour of Macintosh", which contains tutorial demonstrations of the Macintosh system, running on a modified pre-release version of Finder 1.0, as well as training programs for learning to use the mouse, and the Finder. Also included was a 33-minute audio cassette designed to run alongside the demonstrations, emphasising the disk's purpose as a guided tour. Menu bar The menu bar was a new and revolutionary part of the OS. Similar to the one found on Lisa OS, the System 1 Finder had five menus: the Apple menu, File, Edit, View, and Special. When in an application, the menus would change to ones defined by the application, but most software retained at least the File and Edit menus. While within the Finder, the Apple menu contained the "About the Finder" information, along with the desktop accessories. "File" menu items included Open, Eject, and Close. "Edit" had entries for cutting, copying, and pasting. "Special" was used for managing the hardware and other system functions, and was always the rightmost entry on the menu bar in the Finder. In System 1, the menu had items related to emptying the Trash, cleaning up the desktop, and disk options. By System 1.1, the menu allowed the user to choose an alternate startup program to be run instead of the Finder at boot time; the feature was replaced in System 7 by the "Startup Items" folder in the System Folder. Desk accessories System 1 came with multiple desk accessories (DA). These included an Alarm Clock, Calculator, Control Panel, Key Caps, Note Pad, Puzzle, and Scrapbook. A difference between desktop accessories and applications is that multiple desktop accessories could be run at once but only one application could run at a time. Desk accessories could also run on top of an application. Alarm Clock: This DA could be used just like an alarm clock, as the computer would beep, and the menu bar would flash when the alarm's set time was reached. It could also be used as an easier way to change/set the time and date on the computer. When opened, it would show the time and date set on the computer. Calculator: A basic calculator capable of addition, subtraction, multiplication, and division. It featured the basic 18 buttons for input. Control Panel: The control panel was used to adjust some of the settings on the computer. What made the original control panel unique from subsequent Mac OS control panels was the intended absence of any text. This was chosen to demonstrate the graphical user interface. Representation was achieved by using symbols. It could be used to adjust settings such as volume, double click speed, mouse sensitivity, and desktop background. On the Macintosh 128K, Macintosh 512K, and the Macintosh Plus, the screen brightness was controlled by a mechanical adjustment wheel beneath the screen. Key Caps: A DA used to show the layout of the original Macintosh keyboard. It showed what happened when normal keys were pressed along with special characters (Command, Shift, Option). Note Pad: A note taking DA that would save text entered into it on the floppy disk. Multiple note pages could be written when using the folded corner symbol in the bottom left corner of the note page. Puzzle: A basic 1–15 slide puzzle, similar to the picture puzzle found in later versions of the Mac OS. Scrapbook: This DA was similar to a cut, copy, and paste library. In it, one could store text selections and photos which could then be transferred to other applications. See also Apple v. Digital Research GEM/1 Windows 1.0x References External links Macintosh System 1 in your browser—A web-based simulator System 1.0 Headquarters—a walk-through of System 1 with screenshots (from 1998, via archive.org) 1984 software Classic Mac OS

Operating System (OS)

A/UX A/UX (Apple UNIX) is Apple Computer's implementation of the Unix operating system for Macintosh computers, integrated with System 7's graphical interface and application compatibility. Launched in 1988 and discontinued in 1995 with version 3.1.1, it is Apple's first official Unix-based operating system. A/UX requires select models of 68k-based Macintosh with an FPU and a paged memory management unit (PMMU), including the Macintosh II, SE/30, Quadra, and Centris series. It was never the predecessor to macOS, a variant of UNIX currently bundled with Apple's desktop computers. Described by InfoWorld as "an open systems solution with the Macintosh at its heart", the operating system is based on UNIX System V Release 2.2. It includes some additional features from System V Releases 3 and 4 and BSD versions 4.2 and 4.3. It is POSIX- and System V Interface Definition (SVID)-compliant and includes TCP/IP networking from version 2 onward. Having a Unix-compatible, POSIX-compliant operating system made it possible for Apple to bid for large contracts to supply computers to U.S. federal government institutes. Features A/UX provides a graphical user interface including the familiar Finder windows, menus, and controls. The A/UX Finder is a customized version of the System 7 Finder, adapted to run as a Unix process and designed to interact with the underlying Unix file systems. A/UX includes a CommandShell terminal program, which offers a command-line interface to the underlying Unix system. An X Window System server application (called MacX) with a terminal program can also be used to interface with the system and run X applications alongside the Finder. Alternatively, the user can choose to run a fullscreen X11R4 session without the Finder. Apple's compatibility layer allows A/UX to run Macintosh System 7.0.1, Unix, and hybrid applications. A hybrid application uses functions from both the Macintosh toolbox and the Unix system. For example, it can run a Macintosh application which calls Unix system functions, or a Unix application which calls Macintosh Toolbox functions (such as QuickDraw), or a HyperCard stack graphical frontend for a command-line Unix application. A/UX's compatibility layer uses some existing Toolbox functions in the computer's ROM, while other function calls are translated into native Unix system calls; and it cooperatively multitasks all Macintosh apps in a single address space by using a token-passing system for their access to the Toolbox. A/UX includes a utility called Commando (similar to a tool of the same name included with Macintosh Programmer's Workshop) to assist users with entering Unix commands. Opening a Unix executable file from the Finder opens a dialog box that allows the user to choose command-line options for the program using standard controls such as radio buttons and check boxes, and display the resulting command line argument for the user before executing the command or program. This feature is intended to ease the learning curve for users new to Unix, and decrease the user's reliance on the Unix manual. A/UX has a utility that allows the user to reformat third-party SCSI drives in such a way that they can be used in other Macs of that era. A/UX runs only on 68k-based Macintoshes with a floating point unit (FPU) and a paged memory management unit (PMMU); even then, it only runs on select models. For example, the Quadra 840AV, Apple's fastest 68k Macintosh, cannot run A/UX. History A/UX 1.0 was announced at the February 1988 Uniforum conference, seven months behind schedule. It was initially aimed at existing Unix customers, universities and VARs. The system was initially sold pre-installed on the Macintosh II for , although one could add a larger monitor at a higher price, or purchase a kit for upgrading an existing Mac II for a lower price. Third-party software announced with the system's first release includes the Ingres database, StatView, developer tools, and various productivity software packages. Based on AT&T's Unix System V.2.2 with additional features from BSD Unix. Networking support included TCP/IP, AppleTalk, and NFS implementations, developed by UniSoft. The base system had no GUI, running only via the command line. It was capable of running a single Mac program at a time, using the System 6 interface, although only about 10% of the existing Mac software would run on it. Released in 1989, A/UX 1.1 supplies the basic GUI of System 6, with Finder, Chooser, Desk Accessories, and Control Panels; and it provisions Unix with the X Window System (X11R3) GUI, the Draft 12 POSIX standard, and overall improved speed comparable to a low end Sun workstation. Having its first POSIX compliant platform allowed Apple to join "a growing list of industry heavyweights" to be allowed into the US federal government's burgeoning $6 billion bid market. In 1991, based on the AIM alliance, Apple envisioned A/UX as becoming the basis for drastically scaling its concept of Macintosh system architecture and application compatibility across the computing industry, from personal to enterprise markets. Apple formed a new business division for enterprise systems led by director Jim Groff, to serve "large businesses, government, and higher education". Basing the division upon a maturing A/UX, Groff admitted that Apple was "not a major player" in the Unix market and had performed merely "quiet" marketing of the operating system, but fully intended to become a "major player" with "very broad-based marketing objectives" in 1992. Further, Apple believed the alliance with IBM would merge A/UX, AIX, and System 7—thus ultimately scaling the execution of Macintosh applications from Mac desktops to IBM's huge RS/6000 systems. In November 1991, Apple launched A/UX 3.0, planning to synchronize the two ongoing release schedules of A/UX and System 7. At that time, the company also preannounced A/UX 4.0, expected for release in 1993 or 1994. The announcement expounded upon the historic technology partnership between Apple and IBM, expecting to merge Apple's user-friendly graphical interface and desktop applications market with IBM's highly scalable Unix server market, and allowing the two companies to enter what Apple believed to be an emerging "general desktop open systems market". The upcoming A/UX 4.0 would target the PowerOpen Environment ABI, merge features of IBM's AIX variant of Unix into A/UX, and use the OSF/1 kernel from the Open Software Foundation. A/UX 3.0 would serve as an "important migration path" to this new system, making Unix and System 7 applications compliant with the PowerOpen specification. The future A/UX 4.0 and AIX operating systems were intended to run on a variety of IBM's POWER and PowerPC hardware, and on Apple's PowerPC-based hardware. In April 1992, a C2-level secure version of A/UX was released. Coincidentally, the AIM alliance had launched the Apple/IBM partnership corporation Taligent Inc. one month earlier, with the mission of bringing Pink to market as a grandly universal operating system and application framework. Contrary to all announcements, Apple eventually abandoned all plans for A/UX 4.0, never releasing the product. In 1995, PowerOpen was discontinued and Apple withdrew from the Taligent Inc. partnership in December. In 1996, Apple discontinued its Copland project which had spent two years in the public view, intended to become Mac OS 8 and to host Taligent software. From 1996 to 1997, the company deployed a short-lived platform of Apple Network Server systems based upon PowerPC hardware and a customized IBM AIX operating system. Apple's overall failed operating system strategy left it with the badly aged System 7 and no successor. Following its 1996 acquisition of NeXT, Apple introduced 1999's Mac OS X Server, a descendant of the Unix-based NeXTSTEP operating system. The final release of A/UX is version 3.1.1 of 1995. Apple had abandoned the A/UX platform completely by 1996. Reception A/UX 1.0 was criticized in a 1988 InfoWorld review for having a largely command-driven user interface as in other Unix variants, rather than graphical as in System 6; its networking support was praised, though. BYTE in 1989 listed A/UX 1.1 among the "Excellence" winners of the BYTE Awards, stating that it "could make Unix the multitasking operating system of choice during the next decade" and challenge OS/2. Compared to contemporary workstations from other Unix vendors, however, the Macintosh hardware lacks features such as demand paging. The first two versions A/UX consequently suffer from poor performance, and poor sales. Users also complained about the amount of disk space it uses on a standard Macintosh, though comparable to any Unix system. In the August 1992 issue of InfoWorld, the same author favorably reviewed A/UX 3.0, describing it as "an open systems solution with the Macintosh at its heart" where "Apple finally gets Unix right". He praised the GUI, single-button point-and-click installer, one year of personal tech support, the graphical help dialogs, and the user's manuals, saying that A/UX "defies the stereotype that Unix is difficult to use" and is "the easiest version of Unix to learn". Its list price of is much higher than that of "much weaker" competing PC operating systems such as System 7, OS/2, MS-DOS, and Windows 3.1, but low compared to the then prevailing proprietary Unix licenses of more than . The review found the system speed "acceptable but not great" even on the fastest Quadra 950, blaming not the software but the incomplete Unix optimization found in Apple's hardware. Though "a very good value", the system's price-performance ratio was judged as altogether uncompetitive against Sun's SPARCstation 2. The reviewers thought it unlikely for users "to want to buy Macs just to run A/UX" and would have awarded InfoWorlds top score if the OS was not proprietary to Macintosh hardware. Tony Bove of the Bove & Rhodes Report generally complained that "[f]or Unix super-users there is no compelling reason to buy Apple's Unix. For Apple A/UX has always been a way to sell Macs, not Unix; it's a check-off item for users." Legacy Because A/UX requires very specific raw hardware access, the execution of A/UX within Macintosh emulation software was impossible until the 2014 introduction of the Macintosh II emulator named Shoebill. Vintage A/UX users had one central repository for most A/UX applications: an Internet server at NASA called Jagubox. It was administered by Jim Jagielski, who was also the editor of the A/UX FAQ. A/UX Users Group Between January, 1995 and January 2008, the A/UX Users Group met eighteen times, over dinners in conjunction with MacWorld Expo and Mactivity conferences. The dinners were hosted by Brita Meng (of Shiva), Richard Ford (of Apple, then Packeteer), and Bill Woodcock (Zocalo, then Packet Clearing House). See also macOS, Apple's current OS, descended from the Unix-based NeXTSTEP MachTen, Unix in the form of a Mac OS 7 application MacMach, an academic Mach-based Unix experiment providing Mac OS 7 as a Unix application Executor, a third-party reverse-engineered reimplementation of System 7 as a Unix application Macintosh Application Environment, Apple's Mac OS application layer for third-party Unix systems Classic, classic Mac OS applications as a paravirtualized Unix process Star Trek project, System 7 ported as a DOS application for IBM PC clones MkLinux, Apple-sponsored Mach microkernel-based Linux on Macintosh hardware References External links Official A/UX FAQ and Semi-official A/UX FAQ updates A/UX retrospective from 2010 at The Long View A/UX overview and tour A/UX Installation Tutorial and General Info Apple Inc. operating systems Discontinued operating systems Window-based operating systems 1988 software

Operating System (OS)

MSX-DOS MSX-DOS is a discontinued disk operating system developed by Microsoft for the 8-bit home computer standard MSX, and is a cross between MS-DOS 1.25 and CP/M-80 2. MSX-DOS MSX-DOS and the extended BASIC with 3½-inch floppy disk support were simultaneously developed by Microsoft and Spectravideo as a software and hardware standard for the MSX home computer standard, to add disk capabilities to BASIC and to give the system a cheaper software medium than Memory Cartridges, and a more powerful storage system than cassette tape. The standard BIOS of an unexpanded MSX computer did not have any floppy disk support, so the additional floppy disk expansion system came with its own BIOS extension ROM (built-in on the disk controller) called the BDOS. Spectravideo also released an MSX-DOS disk in conjunction with the SVI-707 which could be loaded into an MSX system. Once MSX-DOS has been loaded, the system searches the MSX-DOS disk for the COMMAND.COM file and loads it into memory. It not only added floppy disk support commands to MSX BASIC, but also a booting system, with which it was possible to boot a real disk operating system. In that case, the BDOS bypassed the BASIC ROMs, so that the whole 64 KB of address space of the Z80 microprocessor inside the MSX computer could be used for the DOS or for other boot-able disks, for example disk based games. At the same time, the original BIOS ROMs could still be accessed through a "memory bank switch" mechanism, so that DOS-based software could still use BIOS calls to control the hardware and other software mechanisms the main ROMs supplied. Also, due to the BDOS ROM, basic file access capabilities were available even without a command interpreter by using extended BASIC commands. At initial startup, COMMAND.COM looks for an optional batch file named AUTOEXEC.BAT and, if it exists, executes the commands specified in there. If MSX-DOS is not invoked and Disk BASIC starts, a BASIC program named "AUTOEXEC.BAS" will be carried out instead, if present. One major difference between MSX-DOS and MS-DOS 2.x was that MSX-DOS did not use the "boot sector" on the floppy to boot, but instead booted using the BDOS ROM routines, and, in a fashion much like MS-DOS 1.25, it used the FAT ID value from the first byte of the FAT to select file system parameter profiles for its FAT12 file system instead of from the BIOS Parameter Block (BPB) in the boot sector. Also, because there could be more than one floppy disk controller in two or more cartridge slots, MSX-DOS could boot from several different floppy disk drives. This meant that it was possible to have both, a 5¼" floppy disk drive and a 3½" disk drive, and the user could boot from either one of them depending on which drive had a bootable floppy in it. Commands The following is a list of internal commands supported by MSX-DOS. BASIC COPY DATE DEL DELETE DIR ERASE FORMAT MODE PAUSE REM REN RENAME TIME TYPE VERIFY Development history On 10 August 1983, Paul Allen called Tim Paterson, original author of 86-DOS and MS-DOS 1.x, asking him to do a "Z80 version of MS-DOS" for the MSX standard. At the time, Paterson was busy trying to get the first product of his startup Falcon Systems ready to go, so he suggested a few other developers, but Allen said he had already asked. Allen was in a hurry to get it done and nobody else could meet his timeline. Allen and Paterson finally agreed, and on 17 August, they signed an agreement to do "Z80 MS-DOS 1.25" for US$100,000 and the rights for Paterson's company to distribute MS-DOS 2.0, 2.5, and 3.0 with a hardware product without royalty. For Paterson, this was mostly a translation process. He had already written a Z80-to-8086 assembly language translation program (TRANS.COM). In this case, he was manually translating in the other direction. Because MS-DOS 1.x was modelled after CP/M's API and was able to run CP/M applications that had been source-level translated to 8086, that would mean, MSX-DOS would be able to run CP/M programs directly. For this project, Paterson also wrote a Z80 emulator that ran under MS-DOS, which would allow him to do the entire development project under MS-DOS. The MSX-DOS he was writing had an I/O System layer, that interfaced directly to the I/O System layer of the MS-DOS machine, that was running the emulation. This gave MSX-DOS direct access and control of the disk format. Most of the core code was file management, so this was necessary to test it out. By 2 October 1983, he had Microsoft BASIC and Microsoft M80 macro assembler running under MSX-DOS. He finished coding COMMAND.COM a few days later. He worked out some bugs and demonstrated MSX-DOS to Paul Allen on 11 October. The beta test version was officially delivered on 26 October 1983. It included an easter egg, that printed Paterson's name. The name was encoded with FAT code, so it could not be found by simply searching the file. After delivery of the beta version, the code was sent to ASCII in Japan. They created the I/O System for the MSX machine. That code was developed by Jay Suzuki. He figured out the easter egg and added his name to it. ASCII was having problems getting MSX-DOS working on the actual MSX machine. They had not provided an actual MSX machine to Paterson, and instead flew him to Tokyo on 28 January 1984 to help them. It turned out that ASCII had been modifying the code without telling Paterson, so they were not working from the same code base. Paterson spent three days in Tokyo figuring out the problems and came back to Seattle. Chris Larson from Microsoft and Jay Suzuki visited Paterson in Seattle at the end of February and early March 1984. They brought an MSX machine with an in-circuit emulator (ICE) for debugging. They got everything working and on 23 April 1984, Microsoft accepted delivery and made the final payment for MSX-DOS to Paterson. At the time MSX-DOS was written, there was only one popular disk operating system for 8-bit Intel 8080 compatible microprocessors, which was Digital Research's CP/M-80 system. It was also often used with Z80 systems, because the Z80 used an extended 8080 architecture. Microsoft's own disk operating system was also inspired by CP/M. To be able to run (slightly modified) CP/M software Microsoft decided to implement functionality similar to major parts of the CP/M BIOS, routines that CP/M systems used to do specific disk operating tasks, such as opening files, etc. Instead of basing the command processor on CP/M's CCP, which was known for some user unfriendliness, a command line interpreter (COMMAND.COM) based on its MS-DOS counterpart was used. Microsoft also chose its own FAT12 file system over CP/M's filing methods. This ensured that MSX-DOS floppies could be used on an MS-DOS machine, and that only one single formatting and filing system would be used. This was an important decision, because CP/M disks were often not interchangeable between machines, incompatible disk formatting schemes being a factor in this. Microsoft also added a standard set of disk commands to MSX-DOS that were compatible with MS-DOS but not with CP/M. Finally they converted their pipelining system from MS-DOS to MSX-DOS. The resulting DOS was a system that was much user-friendlier than CP/M, but was (in principle) compatible with major CP/M software packages such as WordStar, Turbo Pascal and the "M80" assembler and "L80" linker. Improved versions Like MS-DOS 1.25, the first version of MSX-DOS did not have subdirectories, but in 1988 it evolved to version 2, offering facilities such as subdirectories, memory management and environment strings. Later versions of MSX computers (MSX-2) added an internal real-time clock, which MSX-DOS could use for time stamping files. Commands The following commands are supported by MSX-DOS version 2. ASSIGN ATDIR ATTRIB BASIC BUFFERS CD CHDIR CHKDSK CLS COMMAND2 CONCAT COPY DATE DEL DIR DISKCOPY ECHO ERA ERASE EXIT FIXDISK FORMAT HELP MD MKDIR MODE MOVE MVDIR PATH PAUSE RAMDISK RD REM REN RENAME RMDIR RNDIR SET TIME TYPE UNDEL VER VERIFY VOL XCOPY XDIR In addition, ASCII provided the following MSX-DOS2 Tools. ADDAUX BEEP BIO BODY BSAVE CAL CALC DUMP EXPAND GREP HEAD KEY LIST LS MENU MORE PATCH SLEEP SORT SPEED TAIL TR UNIQ VIEW WC See also SymbOS 86-DOS MIDAS DOS Plus References Discontinued Microsoft operating systems Disk operating systems CP/M MSX MSX-DOS 1984 software

Operating System (OS)

Junos OS The Junos operating system (Junos OS) used in Juniper Networks network devices creates an environment for accelerating the deployment of services and applications over a single network. One Operating System Unlike other network operating systems that share a common name but splinter into many different programs, Junos OS is a single, cohesive operating system that is shared across all network devices and product lines. Junos OS allows Juniper Networks engineers to develop software features once and share these features across all product lines simultaneously, thus reducing the training for each product and interoperability in production environments. CLI The Junos OS CLI is a text-based command interface for configuring, troubleshooting, and monitoring the Juniper device and network traffic associated with it. It supports two types of command modes. Operational Mode—Monitors hardware status and displays information about network data that passes through or into the hardware. Configuration Mode—Configures the Juniper router, switch, or security device, by adding, deleting, or modifying statements in the configuration hierarchy. FIPS 140-2 Security Compliance For advanced network security, a special version of Junos OS called Junos-FIPS 140-2 Security Compliance is available, providing customers with software tools to configure a network of Juniper Networks devices in a Federal Information Processing Standards (FIPS) environment. Juniper Extension Toolkit (JET) Junos OS offers programming interfaces and the Juniper Extension Toolkit (JET) for developing applications that unlock more value from the network. JET is a standard component of Junos OS, and it runs on all Juniper routers, switches, and security devices. JET simplifies the automation of operational, configuration, and management tasks, providing a rich set of open and customizable APIs for control, management, and data planes. It supports standardized programming languages for application development and communication to the Junos OS fast programmable database through standardized and open data exchange formats. It also opens up Trio and Express ASICs via a set of third-party controller-specific adapters, including SAI, OpenFlow, and P4. Junos Fusion Junos Fusion helps reduce network complexity and operational expenses by enabling multiple distributed devices to be managed as a single, logical device. Two different Junos Fusion architectures are available, one for provider edge and one for enterprise. Junos Node Slicing Node slicing is a Junos OS feature that enables creating multiple partitions from a single physical MX Series router. Each partition behaves as an independent router, with its own dedicated control plane, data plane, and management plane, allowing it to run multiple services on a single physical router. Routing Protocols and Applications Junos OS supports a variety of routing protocols and applications. It also supports class of service (CoS), Ethernet VPN (EVPN), firewall filters and policers, flow monitoring, and Layer 2 features. It's a flexible routing policy language that is used for controlling route advertisements and path selection. Junos OS generally adheres to industry standards for routing and Multiprotocol Label Switching (MPLS). The Junos OS supports high availability mechanisms that are not standard to Unix, such as graceful restart. Secure Boot Secure boot is a significant system security enhancement based on the UEFI standard. It works by safeguarding the BIOS itself from tampering or modification and then maintaining that protection throughout the boot process. The secure boot process begins with secure flash, which ensures that unauthorized changes cannot be made to the firmware. Authorized releases of Junos OS carry a digital signature produced by either Juniper Networks directly or one of its authorized partners. Architecture Junos OS has two different architecture variations: Junos OS is based on the FreeBSD operating system and can run as a guest virtual machine on a Linux VM host. Junos OS Evolved is based on the Linux operating system, and provides direct access to Linux utilities and operations. Both operating systems use the same command-line interface (CLI) user interface, the same applications and features, and the same management and automation tools—but Junos OS Evolved infrastructure has been entirely modernized to enable higher availability, accelerated deployment, greater innovation, and improved operational efficiencies. References External links Juniper Networks to Use Oracle Berkeley DB in JUNOS Software Computer networking Embedded operating systems FreeBSD Juniper Networks Network operating systems 1998 software

Operating System (OS)

Windows system In computing, Windows system may refer to: A Windows box, a computer running Microsoft Windows A windowing system, a type of software used to display graphical windows Microsoft Windows, an operating system

Operating System (OS)

OSv OSv (stylized OSv) is a cloud computing focused computer operating system released on September 16, 2013. It is a special-purpose operating system built to run as a guest on top of a virtual machine, thus it does not include drivers for bare-metal hardware. It is a unikernel, designed to run a single Linux executable or an application written in one of the supported runtime environments (such as Java). For this reason, it does not support a notion of users (it's not a multiuser system) or processes - everything runs in the kernel address space. Using a single address space removes some of the time-consuming operations associated with context switching. It uses large amounts of code from the FreeBSD operating system, in particular the network stack and the ZFS file system. OSv can be managed using a REST Management API and an optional command-line interface written in Lua. References External links Slides introducing the basic concept OSv—Optimizing the Operating System for Virtual Machines—paper presented at the USENIX Annual Technical Conference in 2014 Original announcement Computing platforms Free software operating systems Free software programmed in C++ Software companies of Israel Software using the BSD license

Operating System (OS)

Classic Mac OS The classic Mac OS (System Software) is the series of operating systems developed for the Macintosh family of personal computers by Apple Inc. from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The Macintosh operating system is credited with having popularized the graphical user interface concept. It was included with every Macintosh that was sold during the era in which it was developed, and many updates to the system software were done in conjunction with the introduction of new Macintosh systems. Apple released the original Macintosh on January 24, 1984. The first version of the system software, which had no official name, was partially based on the Lisa OS, which Apple previously released for the Lisa computer in 1983. As part of an agreement allowing Xerox to buy shares in Apple at a favorable price, it also used concepts from the Xerox PARC Alto computer, which former Apple CEO Steve Jobs and other Lisa team members had previewed. This operating system consisted of the Macintosh Toolbox ROM and the "System Folder", a set of files that were loaded from disk. The name Macintosh System Software came into use in 1987 with System 5. Apple rebranded the system as Mac OS in 1996, starting officially with version 7.6, due in part to its Macintosh clone program. That program ended after the release of Mac OS 8 in 1997. The last major release of the system was Mac OS 9 in 1999. Initial versions of the System Software ran one application at a time. With the Macintosh 512K, a system extension called the Switcher was developed to use this additional memory to allow multiple programs to remain loaded. The software of each loaded program used the memory exclusively; only when activated by the Switcher did the program appear, even the Finder's desktop. With the Switcher, the now familiar Clipboard feature allowed copy and paste between the loaded programs across switches including the desktop. With the introduction of System 5, a cooperative multitasking extension called MultiFinder was added, which allowed content in windows of each program to remain in a layered view over the desktop, and was later integrated into System 7 as part of the operating system along with support for virtual memory. By the mid-1990s, however, contemporary operating systems such as Windows NT, OS/2, and NeXTSTEP had all brought pre-emptive multitasking, protected memory, access controls, and multi-user capabilities to desktop computers. The Macintosh's limited memory management and susceptibility to conflicts among extensions that provide additional functionality, such as networking or support for a particular device, led to significant criticism of the operating system, and was a factor in Apple's declining market share at the time. After two aborted attempts at creating a successor to the Macintosh System Software called Taligent and Copland, and a four-year development effort spearheaded by Steve Jobs's return to Apple in 1997, Apple replaced Mac OS with a new operating system in 2001 named Mac OS X; the X signifying the underlying Unix system family base shared with Jobs's development of the NeXTSTEP operating systems on the NeXT computer. It retained most of the user interface design elements of the classic Mac OS, and there was some overlap of application frameworks for compatibility, but the two operating systems otherwise have completely different origins and architectures. The final updates to Mac OS 9 released in 2001 provided interoperability with Mac OS X. The name "Classic" that now signifies the historical Mac OS as a whole is a reference to the Classic Environment, a compatibility layer that helped ease the transition to Mac OS X (now macOS). Initial concept The Macintosh project started in late 1978 with Jef Raskin, who envisioned an easy-to-use, low-cost computer for the average consumer. In September 1979, Raskin began looking for an engineer who could put together a prototype. Bill Atkinson, a member of the Apple Lisa team, introduced Raskin to Burrell Smith, a service technician who had been hired earlier that year. Apple's concept for the Macintosh deliberately sought to minimize the user's awareness of the operating system. Many basic tasks that required more operating system knowledge on other systems could be accomplished by mouse gestures and graphic controls on a Macintosh. This would differentiate it from its contemporaries such as MS-DOS, which use a command-line interface consisting of terse, abbreviated textual commands. In January 1981, Steve Jobs completely took over the Macintosh project. Jobs and a number of Apple engineers visited Xerox PARC in December 1979, three months after the Lisa and Macintosh projects had begun. After hearing about the pioneering GUI technology being developed at Xerox PARC from former Xerox employees like Raskin, Jobs negotiated a visit to see the Xerox Alto computer and Smalltalk development tools in exchange for Apple stock options. The final Lisa and Macintosh operating systems use concepts from the Xerox Alto, but many elements of the graphical user interface were created by Apple including the menu bar, pull-down menus, and the concepts of drag and drop and direct manipulation. Unlike the IBM PC, which uses 8 kB of system ROM for power-on self-test (POST) and basic input/output system (BIOS), the Mac ROM is significantly larger (64 kB) and holds key OS code. Much of the original Mac ROM was coded by Andy Hertzfeld, a member of the original Macintosh team. He was able to conserve precious ROM space by writing routines in assembly language code optimized with "hacks," or clever programming tricks. In addition to the ROM, he also coded the kernel, the Macintosh Toolbox, and some of the desktop accessories (DAs). The icons of the operating system, which represent folders and application software, were designed by Susan Kare, who later designed the icons for Microsoft Windows 3.0. Bruce Horn and Steve Capps wrote the Macintosh Finder, as well as a number of Macintosh system utilities. Apple aggressively advertised their new machine. After its release, the company bought all 39 pages of advertisement space in the 1984 November/December edition of Newsweek magazine. The Macintosh quickly outsold its more sophisticated but much more expensive predecessor, the Lisa. Apple quickly developed MacWorks, a product that allowed the Lisa to emulate Macintosh system software through System 3, by which time it had been discontinued as the rebranded Macintosh XL. Many of the Lisa's operating system advances would not appear in the Macintosh operating system until System 7 or later. Architecture Compatibility Early versions of Mac OS are compatible only with Motorola 68000-family Macintoshes. As Apple introduced computers with PowerPC hardware, the OS was ported to support this architecture. Mac OS 8.1 is the last version that could run on a 68k processor (the 68040). In systems prior to PowerPC G3-based systems, significant parts of the system are stored in physical ROM on the motherboard. The initial purpose of this is to avoid having the OS use up most of the 128KiB RAM of the initial Macintosh—the initial ROMs were 64KiB. This architecture also allows for a completely graphical OS interface at the lowest level without the need for a text-only console or command-line mode: boot time errors, such as finding no functioning disk drives, are communicated to the user graphically, usually with an icon or the distinctive Chicago bitmap font and a Chime of Death or a series of beeps. This is in contrast to MS-DOS and CP/M computers of the time, which display such messages in a mono-spaced font on a black background, and require the use of the keyboard rather than a mouse, for input. To provide such niceties at a low level, early Mac OS depends on core system software in ROM on the motherboard, which also ensured that only Apple computers or licensed clones (with the copyright-protected ROMs from Apple) can run Mac OS. Mac clones Several computer manufacturers over the years made Macintosh clones that were capable of running Mac OS. From 1995 to 1997, Apple licensed Macintosh ROMs to several companies, notably Power Computing, UMAX and Motorola. These machines normally ran various versions of classic Mac OS. Steve Jobs ended the clone-licensing program after returning to Apple in 1997. Support for Macintosh clones was first exhibited in System 7.5.1, which was the first version to include the "Mac OS" logo (a variation on the original Happy Mac startup icon), and Mac OS 7.6 was the first to be named "Mac OS" instead of "System". These changes were made to disassociate the operating system from Apple's own Macintosh models. File systems The Macintosh originally used the Macintosh File System (MFS), a flat file system with only one level of folders. This was quickly replaced in 1985 by the Hierarchical File System (HFS), which had a true directory tree. Both file systems are otherwise compatible. An improved file system named HFS Plus ("HFS+" or "Mac OS Extended") was announced in 1997 and implemented in 1998. Files in most file systems used with DOS, Windows, Unix, or other operating systems have only one "fork". By contrast, MFS and HFS give files two different "forks". The data fork contains the same sort of information as a file in other file systems, such as the text of a document or the bitmaps of an image file. The resource fork contains other structured data such as menu definitions, graphics, sounds, or code segments that would be incorporated into a program's file format on other systems. An executable file might consist only of resources (including code segments) with an empty data fork, while a data file might have only a data fork with no resource fork. A word processor file could contain its text in the data fork and styling information in the resource fork, so that an application which doesn't recognize the styling information can still read the raw text. On the other hand, these forks would provide a challenge to interoperability with other operating systems. In copying or transferring a Mac OS file to a non-Mac system, the default implementations would simply strip the file of its resource fork. Most data files contained only nonessential information in their resource fork, such as window size and location, but program files would be inoperative without their resources. This necessitated such encoding schemes as BinHex and MacBinary, which allowed a user to encode a dual-forked file into a single stream, or inversely take a single stream so-encoded and reconstitute it into a dual-forked file usable by Mac OS. Release history System 1, 2, 3, and 4 As part of Apple's goal of creating a computer with appliance-like simplicity, there is no explicit distinction made between the operating system software and the hardware it runs on. Because of this, early versions of the operating system do not have a distinct name. The software consists of two user-visible files: the System file, and the Finder, an application used for file management that also displays the Desktop. The two files are contained in a folder directory labeled "System Folder", which contains other resource files, like a printer driver, needed to interact with the System. Version numbers of the operating system are based on the version numbers of these two files. System 1.0, 1.1, and 2.0 use a flat file system named Macintosh File System (MFS). The Finder provides virtual folders that could be used to organize files, but these folders are not visible from any other application and do not actually exist on the disk. System 2.0 added support for AppleTalk and the newly introduced LaserWriter to use it. System 2.1 (Finder 5.0) introduced the Hierarchical File System (HFS) which has real directories. This version was specifically to support the Hard Disk 20 and only implements HFS in RAM; startup and most floppy disks remain MFS 400 K volumes. System 3.0 (Finder 5.1) was introduced with the Macintosh Plus, officially implementing HFS, 800K startup drives, support for several new technologies including SCSI and AppleShare, and Trash "bulging" (i.e., when the Trash contains files, it gains a bulged appearance). System 4.0 was released with the Macintosh SE and System 4.1 first shipped with the Macintosh II—these new machines required additional support for the first expansion slots, the Apple Desktop Bus (ADB), internal hard drives and, on the Macintosh II, external color displays and the first Motorola 68020 processor. These releases can only run one application at a time, except for desk accessories, though special application shells such as Multi-Mac or Switcher (discussed under MultiFinder) could work around this. Visible changes are best reflected in the version number of the Finder, where major leaps are found between 1.x, 4.x, 5.x, and 6.x. In the late 1990s, Apple retroactively gave these older releases a single name. System Software 5 Towards the end of 1987, Apple introduced a package titled "Apple Macintosh System Software Update 5.0". For the first time, the Macintosh operating system was offered as a distinct retail product that included four 800K disks and three manuals, at a cost of US$49. The software itself was still freely available through user groups and bulletin board services. While the product box presented this update to the operating system as "version 5.0", this number does not appear in the software itself. Three of the four disks (System Tools 1, System Tools 2 and Utilities 1) are all bootable, and the user can boot off whichever floppy contain the tools the user needs. For instance, System Tools 2 is the only disk with printer drivers, and Utilities 1 is the only disk with Disk First Aid and Apple HD SC Setup. Because the disks are named System Tools, users and the press commonly referred to this version as "System Tools 5.0". The primary new feature of System 5 is MultiFinder, an extension which lets the system run several programs at once. The system uses a cooperative multitasking model, meaning that time is given to the background applications only when the foreground application yields control. A change in system functions that applications were already calling to handle events make many existing applications share time automatically, as well as being allowed to perform tasks in the background. Users can also choose not to use MultiFinder, thereby using a single application at a time. In 1990 InfoWorld tested four multitasking options for PC and Mac, viewing MultiFinder positively overall, but noting that its presence halved the speed of file transfer and printing compared to the single-tasking System 6 without MultiFinder. System Software 6 System Software 6 (also referred to as "System 6") is a consolidation release of the Macintosh system software, producing a complete, stable, and long-lasting operating system. Two major hardware introductions requiring additional support under System 6 are the 68030 processor and 1.44 MB SuperDrive debuting with the Macintosh IIx and Macintosh SE/30. Later updates include support for the first specialized laptop features with the introduction of the Macintosh Portable. From System 6 forward, the Finder has a unified version number closely matching that of the System, alleviating much of the confusion caused by the often considerable differences between earlier Systems. System 7/Mac OS 7 On May 13, 1991, System 7 was released. It is a major upgrade over System 6, adding a significant user interface overhaul, new applications, stability improvements and many new features. Its introduction coincides with the release of and provided support for the 68040 Macintosh line. The System 7 era saw numerous changes in the Macintosh platform including a proliferation of Macintosh models, the 68k to Power Macintosh transition as well as the rise of Microsoft Windows, increasing use of computer networking and the explosion in popularity of the Internet. One of the most significant features of System 7 is virtual memory support, an essential subsystem anticipated for years, which only exists for previous Systems in a third party extension named Virtual from Connectix. Accompanying this was a move to 32-bit memory addressing, necessary for the ever-increasing amounts of RAM available to the Motorola 68030 CPU, and 68020 CPUs with a 68851 PMMU. This process involves making all of the routines in OS code use the full 32-bits of a pointer as an address—prior systems used the upper 8 bits as flags. This change is known as being "32-bit clean". While System 7 itself is 32-bit clean, many existing machines and thousands of applications were not, so it was some time before the process was completed. To ease the transition, the "Memory" control panel contains a switch to disable this feature, allowing for compatibility with older applications. Another notable System 7 feature is built-in cooperative multitasking. In System Software 6, this function was optional through the MultiFinder. System 7 also introduced aliases, similar to symbolic links on Unix, shortcuts that were introduced in later versions of Microsoft Windows, and shadows in IBM OS/2. System extensions were enhanced by being moved to their own subfolder; a subfolder in the System Folder was also created for the control panels. In System 7.5, Apple includes the Extensions Manager, a previously third-party program which simplified the process of enabling and disabling extensions. The Apple menu, home only to desk accessories in System 6, was made more general-purpose: the user could now make often-used folders and applications—or anything else they desired—appear in the menu by placing aliases to them in an "Apple Menu Items" subfolder of the System Folder. System 7 also introduced the following: AppleScript, a scripting language for automating tasks; 32-bit QuickDraw, supporting so-called "true color" imaging, previously available as a system extension; and TrueType, an outline font standard. The Trash, under System 6 and earlier, empties itself automatically when shutting down the computer—or, if MultiFinder is not running, when launching an application. System 7 reimplements the Trash as a special hidden folder, allowing files to remain in it across reboots until the user deliberately chose the "Empty Trash" command. System 7.1 System 7.1 is mainly a bugfix release, with a few minor features added. One of the major new features of System 7.1 was moving fonts out of the System file into the Fonts folder in the System Folder. Previously a resource-copying utility such as ResEdit or Font D/A Mover was required for installing fonts. System 7.1 is not only the first Macintosh operating system to cost money (all previous versions were free or sold at the cost of the floppies), but also received a "Pro" sibling (version 7.1.1) with extra features. System 7.1.2 was the first version to support PowerPC-based Macs. System 7.1 also introduces the System Enablers as a method to support new models without updating the actual System file. This leads to extra files inside the system folder (one per new model supported). System 7.5 System 7.5 introduces a large number of new features, many of which are based on shareware applications that Apple bought and included into the new system. On the newer PowerPC machines, System 7.5 may have stability problems partly due to a new memory manager (which can be turned off), and issues with the handling of errors in the PowerPC code (all PowerPC exceptions map to Type 11). These issues do not affect 68k-architecture machines. System 7.5 is contemporary with Apple's failed Copland effort as well as the release of Windows 95, which coincides with Apple's purchase of several shareware system enhancements to include as new system features. Mac OS 7.6 Stability improved in PowerPC-based Macs with Mac OS 7.6, which dropped the "System" moniker as a more trademarkable name was needed in order to license the OS to the growing market of third-party Macintosh clone manufacturers. Mac OS 7.6 required 32-bit-clean ROMs, and so it dropped support for every Mac with a 68000 processor, as well as the Mac II, Mac IIx, Mac IIcx, and Mac SE/30. Mac OS 8 Mac OS 8 was released on July 26, 1997, the same month Steve Jobs became the de facto CEO of Apple. It was mainly released to keep the Mac OS moving forward during a difficult time for Apple. Initially planned as Mac OS 7.7, it was renumbered "8" to exploit a legal loophole and accomplish Jobs's goal of terminating third-party manufacturers' licenses to System 7 and shutting down the Macintosh clone market. Mac OS 8 added a number of features from the abandoned Copland project, while leaving the underlying operating system unchanged. A multi-threaded Finder was included; files could now be copied in the background. The GUI was changed in appearance to a new shaded greyscale look named Platinum, and the ability to change the appearance themes (also known as skins) was added with a new control panel (though Platinum was the only one shipped). This capability was provided by a new "appearance" API layer within the OS, one of the few significant changes. Apple sold 1.2 million copies of Mac OS 8 in its first two weeks of availability and 3 million within six months. In light of Apple's financial difficulties at the time, there was a large grassroots movement among Mac users to upgrade and "help save Apple". Even some pirate groups refused to redistribute the OS. Mac OS 8.1 Mac OS 8.1 introduced an updated version of the Hierarchical File System named HFS+, which fixed many of the limitations of the earlier system and continued to be used in macOS up until macOS High Sierra, when it was replaced with the Apple File System. There are some other interface changes such as separating network features from printing, and some improvements to application switching. However, in underlying technical respects, Mac OS 8 is not very different from System 7. Mac OS 8.5 Mac OS 8.5 focuses on speed and stability, with most 68k code replaced by modern code native to the PowerPC. It also improved the appearance of the user interface, although the theming feature was cut late in development. Mac OS 9 Mac OS 9, the last major revision of the classic Mac OS, was released on October 23, 1999. It is generally a steady evolution from Mac OS 8. Early development releases of Mac OS 9 were numbered 8.7. Mac OS 9 added improved support for AirPort wireless networking. It introduced an early implementation of multi-user support. Though not a true multi-user operating system, Mac OS 9 does allow multiple desktop users to have their own data and system settings. An improved Sherlock search engine added several new search plug-ins. Mac OS 9 also provides a much improved memory implementation and management. AppleScript was improved to allow TCP/IP and networking control. Mac OS 9 also makes the first use of the centralized Apple Software Update to find and install OS and hardware updates. Other new features included its on-the-fly file encryption software with code signing and Keychain technologies, Remote Networking and File Server packages, and much improved list of USB drivers. Mac OS 9 also added some transitional technologies to help application developers adopt some Mac OS X features before the introduction of the new OS to the public, to help ease the transition. These included new APIs for the file system and the bundling of the Carbon library that apps could link against instead of the traditional API libraries—apps that were adapted to do this could be run natively on Mac OS X as well. Other changes were made beginning with the Mac OS 9.1 update to allow it to be launched in the Classic Environment within Mac OS X. The final update to the classic Mac OS was version 9.2.2, released on December 5, 2001. Transition to Mac OS X macOS (originally named "Mac OS X" until 2012 and then "OS X" until 2016) is Apple's current Mac operating system that officially succeeded the classic Mac OS in 2001. Although it was originally marketed as simply "version 10" of Mac OS, it has a history that is largely independent of the earlier Mac OS releases. The macOS architectural legacy is the successor to Mac OS 9 and the classic Mac OS legacy. However, unlike the classic Mac OS, it is a Unix-based operating system built on NeXTSTEP and technology developed at NeXT from the late 1980s until early 1997, when Apple purchased the company, and its CEO Steve Jobs returned to Apple. macOS also makes use of the BSD codebase and the XNU kernel, and its core set of components is based upon Apple's open source Darwin operating system. An early version of the operating system, Mac OS X Server 1.0, was released in 1999. It retains the "platinum" appearance from the classic Mac OS and even resembles OPENSTEP in places, with the first version to arrive with the new Aqua user interface. The desktop version, Mac OS X 10.0, followed on March 24, 2001, supporting the new Aqua user interface. Since then, several more versions of the operating system have been released. Mac OS X was renamed "OS X" in 2012 and "macOS" in 2016. Users of the classic Mac OS generally upgraded to Mac OS X, but it was criticized in its early years as more difficult and less user-friendly than the original Mac OS, for the lack of certain features that had not yet been reimplemented in the new OS, for being slower on the same hardware (especially older hardware), and for incompatibilities with the older OS. Because drivers (for printers, scanners, tablets, etc.) written for the older Mac OS were not compatible with Mac OS X, inconsistent program support with the Classic Environment program used to run the older operating system's programs on Mac OS X, and the lack of Mac OS X support for older Apple computers before late 1997; some Macintosh users continued using the older classic Mac OS for a few years after the original release of Mac OS X. Steve Jobs encouraged people to upgrade to Mac OS X by staging a mock funeral for Mac OS 9 at WWDC 2002. Classic PowerPC versions of Mac OS X up to and including Mac OS X 10.4 Tiger include a compatibility layer for running older Mac applications, the Classic Environment. Originally codenamed the "blue box", the environment runs a nearly complete Mac OS 9 operating system, version 9.1 or later, as a Mac OS X application. This allows applications that have not been ported to the Carbon API to run on Mac OS X. This is reasonably seamless, though "classic" applications retain their original Mac OS 9 appearance and do not gain the Mac OS X "Aqua" appearance. Early New World ROM PowerPC-based Macs shipped with Mac OS 9.2 as well as Mac OS X. Mac OS 9.2 had to be installed by the user—it was not installed by default on hardware revisions released after Mac OS X 10.4. Most well-written "classic" Mac OS applications function properly under this environment, but compatibility is assured only if the software was written to be unaware of the actual hardware and to interact solely with the operating system. The Classic Environment is not available on Intel-based Mac systems due to the incompatibility of Mac OS 9 with the x86 hardware. Emulation 68k emulators Third-party Macintosh emulators, such as vMac, Basilisk II, and Executor, eventually made it possible to run the classic Mac OS on Intel-based PCs. These emulators were restricted to emulating the 68k series of processors, and as such most couldn't run versions of the Mac OS that succeeded 8.1, which required PowerPC processors. Most also required a Mac ROM image or a hardware interface supporting a real Mac ROM chip; those requiring an image are of dubious legal standing as the ROM image may infringe on Apple's intellectual property. A notable exception was the Executor commercial software product from Abacus Research & Development, the only product that used 100% reverse-engineered code without the use of Apple technology. It ran extremely quickly but never achieved more than a minor subset of functionality. Few programs were completely compatible and many were extremely crash-prone if they ran at all. Executor filled a niche market for porting 68k Mac applications to x86 platforms; development ceased in 2002 and the source code was released by the author in late 2008. Emulators using Mac ROM images offered near complete Mac OS compatibility, and later versions offered excellent performance as modern x86 processor performance increased exponentially. Apple included its own Mac 68k emulator that ran seamlessly on all PowerPC-based versions of the classic Mac OS. PowerPC emulators As of 2021 the most capable PowerPC emulator is QEMU In comparison with 68k-emulator development, PowerPC emulation is more complex and requires more CPU power. The emulator is capable of running Classic Mac OS and OS X at full speed with networking and sound in most cases. QEMU has official support for Classic Mac OS version 9.0 through 9.2 and Mac OS X 10.0 up to and including 10.5. QEMU has several advantages over other PowerPC emulators namely supporting a wide range of platforms from Linux to Mac and Windows on current CPU architectures. Another PowerPC emulator is SheepShaver, which has been around since 1998 for BeOS on the PowerPC platform, but in 2002 was open sourced, and efforts began to port it to other platforms. Originally it was not designed for use on x86 platforms and required an actual PowerPC processor present in the machine it was running on similar to a hypervisor. Although it provides PowerPC processor support, it can run only up to Mac OS 9.0.4 because it does not emulate a memory management unit. Other examples include ShapeShifter (by the same developer that created SheepShaver), Fusion, PearPC and iFusion. The latter ran classic Mac OS with a PowerPC "coprocessor" accelerator card. Using this method has been said to equal or better the speed of a Macintosh with the same processor, especially with respect to the 68k series due to real Macs running in MMU trap mode, hampering performance. Apple's Rosetta was a PowerPC emulator allowing Intel-based Macs to run PowerPC MacOS X applications, but it did not support classic Mac OS (9.2.2 or earlier) applications. Timeline See also List of Apple operating systems Comparison of operating systems History of the graphical user interface Inside Macintosh Apple Computer, Inc. v. Microsoft Corp. List of old Macintosh software Notes References External links Apple Discussions: Classic Mac OS – Apple's official forum for Classic Mac OS The Real History of the GUI – An article about the history of GUIs Apple Macintosh before System 7 – A comprehensive guide to Mac OS releases prior to System 7 Folklore.org – A site of anecdotes shared by the creators of the first Macintosh The Vintage Mac Museum – Information on Macintosh systems from System 1 to System 7 Macintosh System 1 in your browser – A web-based simulator Macintosh System 7 in your browser – A web-based simulator BYTE Magazine September 1986 – A feature on Amiga vs. Macintosh Apple Inc. software History of software Macintosh operating systems Software version histories 1984 software Macintosh operating systems development Discontinued operating systems Pascal (programming language) software

Operating System (OS)

SHARE Operating System The SHARE Operating System (SOS) is an operating system introduced in 1959 by the SHARE user group. It is an improvement on the General Motors GM-NAA I/O operating system, the first operating system for the IBM 704. The main objective was to improve the sharing of programs. The SHARE Operating System provided new methods to manage buffers and input/output devices. Like GM-NAA I/O, it allowed execution of programs written in assembly language. SOS initially ran on the IBM 709 computer and was then ported to its transistorized successor, the IBM 7090. A series of articles describing innovations in the system appears in the April 1959 Journal of the Association for Computing Machinery. In 1962, IBM discontinued support for SOS and announced an entirely new (and incompatible) operating system, IBM 7090/94 IBSYS. See also Multiple Console Time Sharing System Timeline of operating systems SQUOZE References Further reading (5 pages) (7 pages) (4 pages) (NB. This was presented at the ACM meeting 11-13 June 1958.) External links Upload of the SHARE Operating System software and documentation (partial archive) 1959 software Free software operating systems IBM operating systems Discontinued operating systems

Operating System (OS)

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged in a Linux distribution. Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name "GNU/Linux" to emphasize the importance of GNU software, causing some controversy. Popular Linux distributions include Debian, Fedora Linux, and Ubuntu. Commercial distributions include Red Hat Enterprise Linux and SUSE Linux Enterprise. Desktop Linux distributions include a windowing system such as X11 or Wayland, and a desktop environment such as GNOME or KDE Plasma. Distributions intended for servers may omit graphics altogether, or include a solution stack such as LAMP. Because Linux is freely redistributable, anyone may create a distribution for any purpose. Linux was originally developed for personal computers based on the Intel x86 architecture, but has since been ported to more platforms than any other operating system. Because of the dominance of the Linux-based Android on smartphones, Linux also has the largest installed base of all general-purpose operating systems. Although Linux is used by only around 2.3 percent of desktop computers, the Chromebook, which runs the Linux kernel-based Chrome OS, dominates the US K–12 education market and represents nearly 20 percent of sub-$300 notebook sales in the US. Linux is the leading operating system on servers (over 96.4% of the top 1 million web servers' operating systems are Linux), leads other big iron systems such as mainframe computers, and is the only OS used on TOP500 supercomputers (since November 2017, having gradually eliminated all competitors). Linux also runs on embedded systems, i.e. devices whose operating system is typically built into the firmware and is highly tailored to the system. This includes routers, automation controls, smart home technology, televisions (Samsung and LG Smart TVs use Tizen and WebOS, respectively), automobiles (for example, Tesla, Audi, Mercedes-Benz, Hyundai, and Toyota all rely on Linux), digital video recorders, video game consoles, and smartwatches. The Falcon 9's and the Dragon 2's avionics use a customized version of Linux. Linux is one of the most prominent examples of free and open-source software collaboration. The source code may be used, modified and distributed commercially or non-commercially by anyone under the terms of its respective licenses, such as the GNU General Public License. History Precursors The Unix operating system was conceived and implemented in 1969, at AT&T's Bell Labs, in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. First released in 1971, Unix was written entirely in assembly language, as was common practice at the time. In 1973 in a key, pioneering approach, it was rewritten in the C programming language by Dennis Ritchie (with the exception of some hardware and I/O routines). The availability of a high-level language implementation of Unix made its porting to different computer platforms easier. Due to an earlier antitrust case forbidding it from entering the computer business, AT&T was required to license the operating system's source code to anyone who asked. As a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs; freed of the legal obligation requiring free licensing, Bell Labs began selling Unix as a proprietary product, where users were not legally allowed to modify Unix. The GNU Project, started in 1983 by Richard Stallman, had the goal of creating a "complete Unix-compatible software system" composed entirely of free software. Work began in 1984. Later, in 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a command-line shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel, called GNU Hurd, were stalled and incomplete. MINIX was created by Andrew S. Tanenbaum, a computer science professor, and released in 1987 as a minimal Unix-like operating system targeted at students and others who wanted to learn operating system principles. Although the complete source code of MINIX was freely available, the licensing terms prevented it from being free software until the licensing changed in April 2000. Although not released until 1992, due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Linus Torvalds has stated on separate occasions that if the GNU kernel or 386BSD had been available at the time (1991), he probably would not have created Linux. Creation In 1991, while attending the University of Helsinki, Torvalds became curious about operating systems. Frustrated by the licensing of MINIX, which at the time limited it to educational use only, he began to work on his own operating system kernel, which eventually became the Linux kernel. Torvalds began the development of the Linux kernel on MINIX and applications written for MINIX were also used on Linux. Later, Linux matured and further Linux kernel development took place on Linux systems. GNU applications also replaced all MINIX components, because it was advantageous to use the freely available code from the GNU Project with the fledgling operating system; code licensed under the GNU GPL can be reused in other computer programs as long as they also are released under the same or a compatible license. Torvalds initiated a switch from his original license, which prohibited commercial redistribution, to the GNU GPL. Developers worked to integrate GNU components with the Linux kernel, making a fully functional and free operating system. Naming Linus Torvalds had wanted to call his invention "Freax", a portmanteau of "free", "freak", and "x" (as an allusion to Unix). During the start of his work on the system, some of the project's makefiles included the name "Freax" for about half a year. Torvalds had already considered the name "Linux", but initially dismissed it as too egotistical. To facilitate development, the files were uploaded to the FTP server (ftp.funet.fi) of FUNET in September 1991. Ari Lemmke, Torvalds' coworker at the Helsinki University of Technology (HUT), who was one of the volunteer administrators for the FTP server at the time, did not think that "Freax" was a good name, so he named the project "Linux" on the server without consulting Torvalds. Later, however, Torvalds consented to "Linux". According to a newsgroup post by Torvalds, the word "Linux" should be pronounced ( ) with a short 'i' as in 'print' and 'u' as in 'put'. To further demonstrate how the word "Linux" should be pronounced, he included an audio guide () with the kernel source code. However, in this recording, he pronounces 'Linux' ( with a short but close unrounded front vowel. Commercial and popular uptake Adoption of Linux in production environments, rather than being used only by hobbyists, started to take off first in the mid-1990s in the supercomputing community, where organizations such as NASA started to replace their increasingly expensive machines with clusters of inexpensive commodity computers running Linux. Commercial use began when Dell and IBM, followed by Hewlett-Packard, started offering Linux support to escape Microsoft's monopoly in the desktop operating system market. Today, Linux systems are used throughout computing, from embedded systems to virtually all supercomputers, and have secured a place in server installations such as the popular LAMP application stack. Use of Linux distributions in home and enterprise desktops has been growing. Linux distributions have also become popular in the netbook market, with many devices shipping with customized Linux distributions installed, and Google releasing their own Chrome OS designed for netbooks. Linux's greatest success in the consumer market is perhaps the mobile device market, with Android being the dominant operating system on smartphones and very popular on tablets and, more recently, on wearables. Linux gaming is also on the rise with Valve showing its support for Linux and rolling out SteamOS, its own gaming-oriented Linux distribution. Linux distributions have also gained popularity with various local and national governments, such as the federal government of Brazil. Current development Greg Kroah-Hartman is the lead maintainer for the Linux kernel and guides its development. William John Sullivan is the executive director of the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions. Design Many open source developers agree that the Linux kernel was not designed but rather evolved through natural selection. Torvalds considers that although the design of Unix served as a scaffolding, "Linux grew with a lot of mutations – and because the mutations were less than random, they were faster and more directed than alpha-particles in DNA." Eric S. Raymond considers Linux's revolutionary aspects to be social, not technical: before Linux, complex software was designed carefully by small groups, but "Linux evolved in a completely different way. From nearly the beginning, it was rather casually hacked on by huge numbers of volunteers coordinating only through the Internet. Quality was maintained not by rigid standards or autocracy but by the naively simple strategy of releasing every week and getting feedback from hundreds of users within days, creating a sort of rapid Darwinian selection on the mutations introduced by developers." Bryan Cantrill, an engineer of a competing OS, agrees that "Linux wasn't designed, it evolved", but considers this to be a limitation, proposing that some features, especially those related to security, cannot be evolved into, "this is not a biological system at the end of the day, it's a software system." A Linux-based system is a modular Unix-like operating system, deriving much of its basic design from principles established in Unix during the 1970s and 1980s. Such a system uses a monolithic kernel, the Linux kernel, which handles process control, networking, access to the peripherals, and file systems. Device drivers are either integrated directly with the kernel, or added as modules that are loaded while the system is running. The GNU userland is a key part of most systems based on the Linux kernel, with Android being the notable exception. The Project's implementation of the C library works as a wrapper for the system calls of the Linux kernel necessary to the kernel-userspace interface, the toolchain is a broad collection of programming tools vital to Linux development (including the compilers used to build the Linux kernel itself), and the coreutils implement many basic Unix tools. The project also develops Bash, a popular CLI shell. The graphical user interface (or GUI) used by most Linux systems is built on top of an implementation of the X Window System. More recently, the Linux community seeks to advance to Wayland as the new display server protocol in place of X11. Many other open-source software projects contribute to Linux systems. Installed components of a Linux system include the following: A bootloader, for example GNU GRUB, LILO, SYSLINUX, or Gummiboot. This is a program that loads the Linux kernel into the computer's main memory, by being executed by the computer when it is turned on and after the firmware initialization is performed. An init program, such as the traditional sysvinit and the newer systemd, OpenRC and Upstart. This is the first process launched by the Linux kernel, and is at the root of the process tree: in other terms, all processes are launched through init. It starts processes such as system services and login prompts (whether graphical or in terminal mode). Software libraries, which contain code that can be used by running processes. On Linux systems using ELF-format executable files, the dynamic linker that manages the use of dynamic libraries is known as ld-linux.so. If the system is set up for the user to compile software themselves, header files will also be included to describe the interface of installed libraries. Besides the most commonly used software library on Linux systems, the GNU C Library (glibc), there are numerous other libraries, such as SDL and Mesa. C standard library is the library needed to run C programs on a computer system, with the GNU C Library being the standard. For embedded systems, alternatives such as the musl, EGLIBC (a glibc fork once used by Debian) and uClibc (which was designed for uClinux) have been developed, although the last two are no longer maintained. Android uses its own C library, Bionic. Basic Unix commands, with GNU coreutils being the standard implementation. Alternatives exist for embedded systems, such as the copyleft BusyBox, and the BSD-licensed Toybox. Widget toolkits are the libraries used to build graphical user interfaces (GUIs) for software applications. Numerous widget toolkits are available, including GTK and Clutter developed by the GNOME project, Qt developed by the Qt Project and led by The Qt Company, and Enlightenment Foundation Libraries (EFL) developed primarily by the Enlightenment team. A package management system, such as dpkg and RPM. Alternatively packages can be compiled from binary or source tarballs. User interface programs such as command shells or windowing environments. User interface The user interface, also known as the shell, is either a command-line interface (CLI), a graphical user interface (GUI), or controls attached to the associated hardware, which is common for embedded systems. For desktop systems, the default user interface is usually graphical, although the CLI is commonly available through terminal emulator windows or on a separate virtual console. CLI shells are text-based user interfaces, which use text for both input and output. The dominant shell used in Linux is the Bourne-Again Shell (bash), originally developed for the GNU project. Most low-level Linux components, including various parts of the userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks and provides very simple inter-process communication. On desktop systems, the most popular user interfaces are the GUI shells, packaged together with extensive desktop environments, such as KDE Plasma, GNOME, MATE, Cinnamon, LXDE, Pantheon and Xfce, though a variety of additional user interfaces exist. Most popular user interfaces are based on the X Window System, often simply called "X". It provides network transparency and permits a graphical application running on one system to be displayed on another where a user may interact with the application; however, certain extensions of the X Window System are not capable of working over the network. Several X display servers exist, with the reference implementation, X.Org Server, being the most popular. Server distributions might provide a command-line interface for developers and administrators, but provide a custom interface towards end-users, designed for the use-case of the system. This custom interface is accessed through a client that resides on another system, not necessarily Linux based. Several types of window managers exist for X11, including tiling, dynamic, stacking and compositing. Window managers provide means to control the placement and appearance of individual application windows, and interact with the X Window System. Simpler X window managers such as dwm, ratpoison, i3wm, or herbstluftwm provide a minimalist functionality, while more elaborate window managers such as FVWM, Enlightenment or Window Maker provide more features such as a built-in taskbar and themes, but are still lightweight when compared to desktop environments. Desktop environments include window managers as part of their standard installations, such as Mutter (GNOME), KWin (KDE) or Xfwm (xfce), although users may choose to use a different window manager if preferred. Wayland is a display server protocol intended as a replacement for the X11 protocol; , it has not received wider adoption. Unlike X11, Wayland does not need an external window manager and compositing manager. Therefore, a Wayland compositor takes the role of the display server, window manager and compositing manager. Weston is the reference implementation of Wayland, while GNOME's Mutter and KDE's KWin are being ported to Wayland as standalone display servers. Enlightenment has already been successfully ported since version 19. Video input infrastructure Linux currently has two modern kernel-userspace APIs for handling video input devices: V4L2 API for video streams and radio, and DVB API for digital TV reception. Due to the complexity and diversity of different devices, and due to the large number of formats and standards handled by those APIs, this infrastructure needs to evolve to better fit other devices. Also, a good userspace device library is the key of the success for having userspace applications to be able to work with all formats supported by those devices. Development The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open-source software. Linux is not the only such operating system, although it is by far the most widely used. Some free and open-source software licenses are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU General Public License (GPL), is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU Project. Linux-based distributions are intended by developers for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX, SUS, LSB, ISO, and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT. Free software projects, although developed through collaboration, are often produced independently of each other. The fact that the software licenses explicitly permit redistribution, however, provides a basis for larger-scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a Linux distribution. Many Linux distributions manage a remote collection of system software and application software packages available for download and installation through a network connection. This allows users to adapt the operating system to their specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more generally integration of the different software packages into a coherent whole. Distributions typically use a package manager such as apt, yum, zypper, pacman or portage to install, remove, and update all of a system's software from one central location. Community A distribution is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis, Debian being a well-known example. Others maintain a community version of their commercial distributions, as Red Hat does with Fedora, and SUSE does with openSUSE. In many cities and regions, local associations known as Linux User Groups (LUGs) seek to promote their preferred distribution and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. Many Internet communities also provide support to Linux users and developers. Most distributions and free software / open-source projects have IRC chatrooms or newsgroups. Online forums are another means for support, with notable examples being LinuxQuestions.org and the various distribution specific support and community forums, such as ones for Ubuntu, Fedora, and Gentoo. Linux distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list. There are several technology websites with a Linux focus. Print magazines on Linux often bundle cover disks that carry software or even complete Linux distributions. Although Linux distributions are generally available without charge, several large corporations sell, support, and contribute to the development of the components of the system and of free software. An analysis of the Linux kernel in 2017 showed that well over 85% of the code developed by programmers who are being paid for their work, leaving about 8.2% to unpaid developers and 4.1% unclassified. Some of the major corporations that provide contributions include Intel, Samsung, Google, AMD, Oracle and Facebook. A number of corporations, notably Red Hat, Canonical and SUSE, have built a significant business around Linux distributions. The free software licenses, on which the various software packages of a distribution built on the Linux kernel are based, explicitly accommodate and encourage commercialization; the relationship between a Linux distribution as a whole and individual vendors may be seen as symbiotic. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks. Another business model is to give away the software to sell hardware. This used to be the norm in the computer industry, with operating systems such as CP/M, Apple DOS and versions of Mac OS prior to 7.6 freely copyable (but not modifiable). As computer hardware standardized throughout the 1980s, it became more difficult for hardware manufacturers to profit from this tactic, as the OS would run on any manufacturer's computer that shared the same architecture. Programming on Linux Most programming languages support Linux either directly or through third-party community based ports. The original development tools used for building both Linux applications and operating system programs are found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU Build System. Amongst others, GCC provides compilers for Ada, C, C++, Go and Fortran. Many programming languages have a cross-platform reference implementation that supports Linux, for example PHP, Perl, Ruby, Python, Java, Go, Rust and Haskell. First released in 2003, the LLVM project provides an alternative cross-platform open-source compiler for many languages. Proprietary compilers for Linux include the Intel C++ Compiler, Sun Studio, and IBM XL C/C++ Compiler. BASIC in the form of Visual Basic is supported in such forms as Gambas, FreeBASIC, and XBasic, and in terms of terminal programming or QuickBASIC or Turbo BASIC programming in the form of QB64. A common feature of Unix-like systems, Linux includes traditional specific-purpose programming languages targeted at scripting, text processing and system configuration and management in general. Linux distributions support shell scripts, awk, sed and make. Many programs also have an embedded programming language to support configuring or programming themselves. For example, regular expressions are supported in programs like grep and locate, the traditional Unix MTA Sendmail contains its own Turing complete scripting system, and the advanced text editor GNU Emacs is built around a general purpose Lisp interpreter. Most distributions also include support for PHP, Perl, Ruby, Python and other dynamic languages. While not as common, Linux also supports C# (via Mono), Vala, and Scheme. Guile Scheme acts as an extension language targeting the GNU system utilities, seeking to make the conventionally small, static, compiled C programs of Unix design rapidly and dynamically extensible via an elegant, functional high-level scripting system; many GNU programs can be compiled with optional Guile bindings to this end. A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM's J2SE RE, as well as many open-source projects like Kaffe and JikesRVM. GNOME and KDE are popular desktop environments and provide a framework for developing applications. These projects are based on the GTK and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated development environments available including Anjuta, Code::Blocks, CodeLite, Eclipse, Geany, ActiveState Komodo, KDevelop, Lazarus, MonoDevelop, NetBeans, and Qt Creator, while the long-established editors Vim, nano and Emacs remain popular. Hardware support The Linux kernel is a widely ported operating system kernel, available for devices ranging from mobile phones to supercomputers; it runs on a highly diverse range of computer architectures, including the hand-held ARM-based iPAQ and the IBM mainframes System z9 or System z10. Specialized distributions and kernel forks exist for less mainstream architectures; for example, the ELKS kernel fork can run on Intel 8086 or Intel 80286 16-bit microprocessors, while the µClinux kernel fork may run on systems without a memory management unit. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as Macintosh computers (with both PowerPC and Intel processors), PDAs, video game consoles, portable music players, and mobile phones. There are several industry associations and hardware conferences devoted to maintaining and improving support for diverse hardware under Linux, such as FreedomHEC. Over time, support for different hardware has improved in Linux, resulting in any off-the-shelf purchase having a "good chance" of being compatible. In 2014, a new initiative was launched to automatically collect a database of all tested hardware configurations. Uses Market share and uptake Many quantitative studies of free/open-source software focus on topics including market share and reliability, with numerous studies specifically examining Linux. The Linux market is growing, and the Linux operating system market size is expected to see a growth of 19.2% by 2027, reaching $15.64 billion, compared to $3.89 billion in 2019. Analysts and proponents attribute the relative success of Linux to its security, reliability, low cost, and freedom from vendor lock-in. Desktops and laptops According to web server statistics (that is, based on the numbers recorded from visits to websites by client devices), , the estimated market share of Linux on desktop computers is around 2.1%. In comparison, Microsoft Windows has a market share of around 87%, while macOS covers around 9.7%. Web servers W3Cook publishes stats that use the top 1,000,000 Alexa domains, which estimate that 96.55% of web servers run Linux, 1.73% run Windows, and 1.72% run FreeBSD. W3Techs publishes stats that use the top 10,000,000 Alexa domains and the top 1,000,000 Tranco domains, updated monthly and as of November 2020 estimate that Linux is used by 39% of the web servers, versus 21.9% being used by Microsoft Windows. 40.1% used other types of Unix. IDC's Q1 2007 report indicated that Linux held 12.7% of the overall server market at that time; this estimate was based on the number of Linux servers sold by various companies, and did not include server hardware purchased separately that had Linux installed on it later. Mobile devices Android, which is based on the Linux kernel, has become the dominant operating system for smartphones. During the second quarter of 2013, 79.3% of smartphones sold worldwide used Android. Android is also a popular operating system for tablets, being responsible for more than 60% of tablet sales as of 2013. According to web server statistics, Android has a market share of about 71%, with iOS holding 28%, and the remaining 1% attributed to various niche platforms. Film production For years Linux has been the platform of choice in the film industry. The first major film produced on Linux servers was 1997's Titanic. Since then major studios including DreamWorks Animation, Pixar, Weta Digital, and Industrial Light & Magic have migrated to Linux. According to the Linux Movies Group, more than 95% of the servers and desktops at large animation and visual effects companies use Linux. Use in government Linux distributions have also gained popularity with various local and national governments. News of the Russian military creating its own Linux distribution has also surfaced, and has come to fruition as the G.H.ost Project. The Indian state of Kerala has gone to the extent of mandating that all state high schools run Linux on their computers. China uses Linux exclusively as the operating system for its Loongson processor family to achieve technology independence. In Spain, some regions have developed their own Linux distributions, which are widely used in education and official institutions, like gnuLinEx in Extremadura and Guadalinex in Andalusia. France and Germany have also taken steps toward the adoption of Linux. North Korea's Red Star OS, developed since 2002, is based on a version of Fedora Linux. Copyright, trademark, and naming Linux kernel is licensed under the GNU General Public License (GPL), version 2. The GPL requires that anyone who distributes software based on source code under this license must make the originating source code (and any modifications) available to the recipient under the same terms. Other key components of a typical Linux distribution are also mainly licensed under the GPL, but they may use other licenses; many libraries use the GNU Lesser General Public License (LGPL), a more permissive variant of the GPL, and the X.Org implementation of the X Window System uses the MIT License. Torvalds states that the Linux kernel will not move from version 2 of the GPL to version 3. He specifically dislikes some provisions in the new license which prohibit the use of the software in digital rights management. It would also be impractical to obtain permission from all the copyright holders, who number in the thousands. A 2001 study of Red Hat Linux 7.1 found that this distribution contained 30 million source lines of code. Using the Constructive Cost Model, the study estimated that this distribution required about eight thousand person-years of development time. According to the study, if all this software had been developed by conventional proprietary means, it would have cost about to develop in in the United States. Most of the source code (71%) was written in the C programming language, but many other languages were used, including C++, Lisp, assembly language, Perl, Python, Fortran, and various shell scripting languages. Slightly over half of all lines of code were licensed under the GPL. The Linux kernel itself was 2.4 million lines of code, or 8% of the total. In a later study, the same analysis was performed for Debian version 4.0 (etch, which was released in 2007). This distribution contained close to 283 million source lines of code, and the study estimated that it would have required about seventy three thousand man-years and cost (in dollars) to develop by conventional means. In the United States, the name Linux is a trademark registered to Linus Torvalds. Initially, nobody registered it, but on August 15, 1994, William R. Della Croce, Jr. filed for the trademark Linux, and then demanded royalties from Linux distributors. In 1996, Torvalds and some affected organizations sued him to have the trademark assigned to Torvalds, and, in 1997, the case was settled. The licensing of the trademark has since been handled by the Linux Mark Institute (LMI). Torvalds has stated that he trademarked the name only to prevent someone else from using it. LMI originally charged a nominal sublicensing fee for use of the Linux name as part of trademarks, but later changed this in favor of offering a free, perpetual worldwide sublicense. The Free Software Foundation (FSF) prefers GNU/Linux as the name when referring to the operating system as a whole, because it considers Linux distributions to be variants of the GNU operating system initiated in 1983 by Richard Stallman, president of the FSF. They explicitly take no issue over the name Android for the Android OS, which is also an operating system based on the Linux kernel, as GNU is not a part of it. A minority of public figures and software projects other than Stallman and the FSF, notably Debian (which had been sponsored by the FSF up to 1996), also use GNU/Linux when referring to the operating system as a whole. Most media and common usage, however, refers to this family of operating systems simply as Linux, as do many large Linux distributions (for example, SUSE Linux and Red Hat Enterprise Linux). By contrast, Linux distributions containing only free software use "GNU/Linux" or simply "GNU", such as Trisquel GNU/Linux, Parabola GNU/Linux-libre, BLAG Linux and GNU, and gNewSense. , about 8% to 13% of a modern Linux distribution is made of GNU components (the range depending on whether GNOME is considered part of GNU), as determined by counting lines of source code making up Ubuntu's "Natty" release; meanwhile, 6% is taken by the Linux kernel, increased to 9% when including its direct dependencies. See also Comparison of Linux distributions Comparison of open source and closed source Comparison of operating systems Comparison of X Window System desktop environments Criticism of Linux Linux Documentation Project Linux From Scratch Linux Software Map List of Linux distributions List of games released on Linux List of operating systems Loadable kernel module Notes References External links Graphical map of Linux Internals Linux kernel website and archives The History of Linux in GIT Repository Format 1992–2010 1991 software Computing platforms Cross-platform software Finnish inventions Linus Torvalds Unix variants Free software programmed in C Operating systems

Operating System (OS)

Hackintosh A Hackintosh (a portmanteau of "Hack" and "Macintosh") is a computer that runs Apple's Macintosh operating system macOS (formerly named "Mac OS X" or "OS X") on computer hardware not authorized for the purpose by Apple. "Hackintoshing" began as a result of Apple's 2005 transition to Intel processors, away from PowerPC. Since 2005, Mac computers use the same x86-64 computer architecture as many other desktop PCs, laptops, notebooks and servers, meaning that in principle, the code making up macOS systems and software can be run on alternative platforms with minimal compatibility issues. Benefits cited for "Hackintoshing" can include cost (older, cheaper or commodity hardware), ease of repair and piecemeal upgrade, and freedom to use customized choices of components that are not available (or not available together) in the branded Apple products. macOS can also be run on several non-Apple virtualization platforms, although such systems are not usually described as Hackintoshes. Hackintosh laptops are sometimes referred to as "Hackbooks". In recent years, the use of AMD processors has become common in Hackintoshes, thanks to the website AMD OS X. The popularity is due to the introduction of the powerful AMD Ryzen and Threadripper CPUs. Apple's software license for macOS only permits the software's use on computers that are "Apple-branded." However, because modern Macintosh computers use Intel-based hardware, there are few limitations keeping the software from running on other types of Intel-based PCs. Notably, companies such as Psystar have attempted to release products using macOS on non-Apple machines, though many Hackintosh systems are designed solely by macOS enthusiasts of various hacking forums and communities. While the methods Apple uses to prevent macOS from being installed on non-Apple hardware are protected from commercial circumvention in the United States by the Digital Millennium Copyright Act (DMCA), specific changes to the law regarding the concept of jailbreaking have placed circumvention methods like these into a legal grey area. In 2020, Apple began to move to ARM64-based Apple silicon processors. The company has said it will eventually stop supporting the Intel64 architecture. History Mac OS X Tiger (10.4) On June 6, 2005, Apple announced its plans to transition to Intel x86 processors at their Worldwide Developers Conference and made available a prototype Intel-based Mac to selected developers at a cost of $999 (). Efforts immediately began to attempt to run Mac OS X on non-Apple hardware, but developers quickly found themselves with an error message saying that the PC hardware configurations were not supported. On January 10, 2006, Apple released 10.4.4 with the first generation of Intel-based Macs, the iMac and the MacBook Pro. These machines used Extensible Firmware Interface (EFI) platform firmware instead of the older style BIOS found on most x86 motherboards at the time. On February 14, 2006, an initial "hack" of v10.4.4 was released on the Internet by a programmer with the pseudonym crg92. Within hours Apple released the 10.4.5 update, which was then hacked by the same author within two weeks. On April 3, 2006 Apple released their 10.4.6 update and again patches were released within two weeks that allowed users to install most of this update on non-Apple computers, although this did not include the updated kernel in 10.4.6. In June 2006, an updated MacBook Pro was released for the 10.4.7 update for non-Apple computers using the 10.4.4 kernel. Up to the release of the 10.4.8 update, all OSx86 patches used the 10.4.4 kernel with the rest of the operating system at version 10.4.8. However, the newer frameworks relied on the newer kernels and this led to users of 10.4.8 encountering many problems. Apple also started making more use of SSE3 instructions on their hardware making it even more difficult for users with CPUs supporting only SSE2 (such as older Pentium 4s) to get a fully compatible system running. To solve this problem, hackers from the community released kernels where those instructions were emulated with SSE2 equivalents, although this produced a performance penalty. Throughout the years, many "distros" were released for download over the Internet. These distros were copies of the Mac OS X installer disc modified to include additional components necessary to make the OS run on the non-Apple hardware. A prominent member of the community, JaS, released many distros of Mac OS X Tiger containing patched kernels. Some other popular distros are iATKOS, Kalyway, iPC and iDeneb. Distros have fallen out of favour as the OSx86 community grew, as new bootloaders were developed that made it possible to use actual copies of the OS X Installer. Mac OS X Leopard (10.5) As early as v10.5 build 9A466 the community has maintained a version of Leopard that can run on non-Apple hardware. A hacker by the handle of BrazilMac created one of the earliest patching processes that made it convenient for users to install onto 3rd party hardware by using a legally obtained, retail version of Apple . This simplification made the BrazilMac patch and its later revisions quickly the most popular choice for many distros. Five of the most popular builds go by the name JaS, Kalyway, iATKOS, iPC and iDeneb - although more recently these builds are on the way out as the Boot-132 method (described below) gains popularity. However, all of these compilations rely on the work of kernel hackers made by Lorem (build 9A466), SynthetiX (builds 9A499, 9A527 and 9A559), ToH (builds 9A581, 9B13 and 9B18) and more recently a group calling themselves StageXNU (now called Voodoo) (Darwin 9.4.0). Their contributions trickled down into the various Mac OSx86 installers, readily available on the Internet. They continue to be refined and updated builds released, not just to maintain compatibility with Apple releases but an ever-increasing number of third-party components. The OSx86 community has been quick to make the necessary modifications to enable Apple's latest releases to run on non-Apple hardware. Within hours of Leopard's release, an AMD/Intel SSE2/3 Kernel Patcher was created that removed the HPET requirement from an original untouched mach_kernel file, a core component of the Mac OS. Mac OS X Snow Leopard (10.6) When "Snow Leopard" was released, Russian hacker netkas created a version of Chameleon that can boot Mac OS X v10.6. The main problem was that many people were forced to modify DSDT or use kexts due to some specific issues. As soon as possible modbin and dmitrik released test versions of kernel that allow to boot Snow Leopard on AMD machines. Stable XNU kernels for v10.6 were released by Qoopz and Pcj. There are some popular builds based on Retail by the name Universal (Intel only), Hazard, and iAtkos. Since v10.6.2 Nawcom, Qoopz, and Andy Vandijck have been working on Legacy kernel for unsupported CPUs. Mac OS X Lion (10.7) When Apple released the Developer Preview 1, a Russian Hackintosh developer usr-sse2 was the first who created a method to install Lion. The method consists of deploying Mac OS X v10.7 image on a flash drive, and booting from it via XPC UEFI Bootloader (See DUET below). After some changes were made to the Chameleon source code, it became possible to boot Lion with an updated version of Chameleon. After a while Dmitrik also known as Bronzovka had luck with creating a kernel that supported AMD systems; after a few months (10.7.3 V2 With AMD Support) and iAtkos L2 (10.7.2 Only Intel) were released. OS X Mountain Lion (10.8) Shortly after the release of Developer Preview 1, some unknown developers managed to install this version of OS X to their PC by using a modified version of the Chameleon Bootloader. This version was released via the main project starting at version r1997 to the general public. Due to the problems sourced during the Lion era, other ways of installing and required patches were never made public, which leaves the scene in an unknown state towards Mountain Lion. Since the retail release of Mountain Lion several users have reported successful setups using installers purchased from the Mac App Store, along with updated versions of Chameleon and other tools including distros. Niresh's Distro (10.8 Intel only) was first released and then was updated to 10.8.2 (With AMD and Intel) and 10.8.5 (With UEFI Support, AMD and Intel Support) versions; iAtkos ML2 was released after Niresh's Release. OS X Mavericks (10.9) Multiple new kernels for Hackintosh 10.9 are in the works, although there still are minor issues with most of them. Most of these kernels aim to allow users to run Mavericks on AMD and older Intel CPUs, which lack certain instruction sets of the latest Intel CPUs. Significant efforts have been made to emulate instruction sets like SSSE3, which are not present on AMD K10-based CPUs, and older Intel CPUs, like the Intel Core Duo. AMD's latest CPUs, from the 'Bulldozer' architecture onwards, contain almost all the latest instruction sets, and hence, some kernels with full SSE4 support have also been released. After two months, Niresh's Distro was released for Mavericks, which supports AMD CPUs and latest Intel CPUs. It also has a custom kernel that allows Intel Atom processors to boot into Mavericks. Niresh's was the only free distro that was released for Mavericks, since the iAtkos Team decided to release their Mavericks distro for specific hardware on donation basis. OS X Yosemite (10.10) After the initial release of OS X Yosemite 10.10 BETA, various developers took on the role of updating their bootloaders for the system. Members of OSx86 forum InsanelyMac set to update the EFI Bootloader Chameleon for this new OS release. Some time later, Niresh (an independent OSx86 developer) released a standalone tool known as Yosemite Zone, which would automatically install the new OS and other various features on a non-Apple device with minimal input. This method consisted of torrenting an OS X 10.10 DMG onto a USB flash drive with MacPwn Vanilla Installation. Unibeast was updated to support Yosemite, and a distribution of Yosemite Zone was released with AMD processor support. A vanilla installation of Yosemite is possible via Insanelymac's Pandora Box Beta 2.0 and UniBeast. This type installation uses as few kexts (drivers) as possible in addition to using an unaltered version of the OS X installation app, and is preferred over distributions. OS X El Capitan (10.11) Both Clover and Chameleon were updated to be compatible with El Capitan. Unibeast and MacPwn were updated to support El Capitan as well, since El Capitan, Unibeast (and Multibeast) use the Clover bootloader instead of Chimera (a Chameleon-based bootloader). macOS Sierra (10.12) Clover and Chameleon were updated to be compatible with Sierra. UniBeast, Pandora Box and MacPwn were updated to support it and a distribution of Sierra Zone (10.12.3) was released with AMD processor support. macOS High Sierra (10.13) Clover, MacPwn, OpenCore and UniBeast were updated to support it. A distro of High Sierra Zone by Hackintosh Zone (10.13) was released with AMD Processor support including Ryzen CPUs. macOS Mojave (10.14) Clover was updated to support Mojave with revision 4514. UniBeast also received Mojave support for Intel-based machines. A distro of Hackintosh Mojave by Hackintosh Zone (10.14) was released. Apple has also discontinued support for NVIDIA Web Drivers from the first release of macOS Mojave, to current. macOS Catalina (10.15) Clover r4945 was the first version of Clover to support macOS Catalina, beginning with the first developer beta of macOS Catalina 10.15. UniBeast was updated for macOS Catalina support, but there has not yet been a MultiBeast release for Catalina. For the first public stable release of macOS 10.15, AMD patches were also released, allowing the booting of macOS Catalina on AMD CPU systems. A new bootloader began to emerge during this time, called OpenCore. OpenCore is a successor to Clover, and a necessity for AMD users beyond macOS 10.15.2. macOS Big Sur (11) Although macOS Big Sur will still work on Intel processors, Apple began in 2020 to move to ARM64-based Apple silicon processors, and will eventually stop supporting the Intel64 architecture. This may mean the end of Hackintosh computers in their current form. macOS Monterey (12) In macOS Monterey, some of the new features are exclusive to the ARM64-based Apple M-Series processors and are not available on Intel processors. Legal issues and Apple’s objections Apple does not authorize the use of Mac OS X on any x86 PC other than those which it has manufactured. After announcing its switch to Intel's chips, the company used technical means (although not the Trusted Platform Module, or TPM, as has been widely misreported), to tie Mac OS to the systems it distributed to developers. The macOS EULA forbids installations of macOS on a "non-Apple-branded computer". On 3 July 2008, Apple filed a lawsuit against Psystar Corporation for violating this restriction, among other claims. Apple claimed Psystar "violated the Digital Millennium Copyright Act (DMCA) by dodging copy-protection technologies Apple uses to protect ." Apple employs technological protection measures that effectively control access to Apple's copyrighted works. Specifically, Apple charged Psystar with acquiring or creating code that "avoids, bypasses, removes, descrambles, decrypts, deactivates or impairs a technological protection measure without Apple's authority for the purpose of gaining unauthorized access to Apple's copyrighted works." The legal brief revealed that Apple considers the methods that it uses to prevent macOS from being installed on non-Apple hardware to be protected by the Digital Millennium Copyright Act (DMCA). On 13 November 2009, the court granted Apple's motion for summary judgment and found Apple's copyrights were violated as well as the DMCA when Psystar installed Apple's operating system on non-Apple computers. A hearing on remedies was set for 14 December. On 14 January 2009, the Gadget Lab site of Wired Magazine posted a video tutorial for installing on an MSI Wind netbook, but removed it following a complaint from Apple. Textual instructions remain, but include an EULA violation disclaimer. On 15 May 2012, the case Apple vs. Psystar Corporation ended. The court ruled that Psystar had "violated Apple's exclusive reproduction right, distribution right, and right to create derivative works," putting an end to the case. Hacking approaches Kernel hacks When copies of Mac OS X Tiger started running on non-Apple hardware, it was found that some processors were unable to run the OS. Rosetta, a binary translator that made it possible to run PowerPC programs on Intel processors, (and later the kernel itself) required the support of the SSE3 instruction set. To circumvent this, programmers in the community released patched kernels, which included support for emulating SSE3 instructions using SSE2 equivalents. In October 2005, Apple released update 10.4.3 to developers that required NX bit microprocessor support; however, patches were released to circumvent this as well. Patched kernels were also later released that supported AMD processors. When Mac OS X Leopard released on October 26, 2007, patches were created to remove the HPET requirement from the kernel. Efforts were also made to emulate the SSSE3 instruction set for processors that did not support it. The kernel used by OS X Mavericks made use of SSSE3 instructions, requiring those patches. Boot loaders and emulators EFI emulation Extensible Firmware Interface (EFI) is a specification that defines a software interface between an operating system and platform firmware. Since emulating the EFI does not generally require copying or modifying macOS, it is considered by some hackers to be the legal way of installing macOS on non-Apple computers (despite being untested in courts). The work started with EFI emulation in the form of David Elliot (dfe)'s modified version of Boot-132 called "Darwin/x86", which has a "FakeEFI" system that emulates EFI. In early November 2007, a group of hackers (fronted by a Russian hacker known as Netkas), using Elliot's code, developed a method of emulating an EFI environment using a specially modified Darwin bootloader. In practical terms, this meant that regular PCs meeting a set of hardware requirements could now be "seen" as real Macintosh computers by the OS, allowing the use of unmodified, "stock" Apple kernels (as long as the CPU supports it) and thus giving more transparent and reliable operation. Several methods for real world deployment of this innovative solution have arisen around the Internet. An explanation of this achievement along with a usage guide was provided by the website DigitMemo.com. True EFI emulation was a highly sought after asset for the OSx86 community. Previous efforts based upon Apple's open source Darwin Project and Hackintosh gurus allowed users to use macOS on normal PCs, with patched kernels/kernel modules that simply bypassed EFI. Using the EFI patch, a Hackintosh could boot off "vanilla" (unmodified) macOS kernels and use vanilla kernel extensions. This not only allowed the system to be compatible with future system updates, but also offered increased stability. This method also circumvents one aspect of Apple's End User License Agreement, which states that the modification of non-Open Source components of the OS is forbidden. In mid-2008, a new commercial product, EFi-X, was released that claims to allow full, simple booting off official Leopard install disks, and a subsequent install, without any patching required, but this is possibly a repackaging of Boot-132 technology in a USB-attached device. Rebel EFI is another commercial product that also seems to use Open Source software. It was thought that Windows 7's support of EFI would result in PC motherboards replacing BIOS with EFI. MSI announced the Efinity mainboard in early 2008. As of 2011, EFI-based computers have entered the market, however none can natively boot Mac OS X due to the lack of a HFS+ driver in the EFI implementation. Boot-132 Boot-132 is a bootloader provided by Apple for loading the XNU kernel. In mid-2008, a new modified BOOT-132 came on to the scene. This method allows users to conduct the Leopard-based OSx86 installation using a stock, retail-purchased copy of Leopard and eradicates the necessity of a hacked installation like JaS or Kalyway (mentioned previously). The Boot-132 bootloader essentially preloads an environment on the system from which Leopard can boot and operate. The bootloader stores the necessary files (kext files) in a .img collection or simply a folder. The luxury of this new installation method includes the ability to boot and install from a retail Leopard DVD and update straight from Apple without breaking the DMCA. The only possible problem here is that it breaks the macOS EULA. The bootloader behaves like the Linux kernel: one can use an mboot-compatible (a patched syslinux was used for the hack) bootloader that tells boot-dfe about the .img file (the ramdisk or initrd, as it's known by Linux users), and boot-dfe will then use the kexts (or mkext) from it. This new boot-dfe has been tested with the retail Leopard DVD, and it can boot, install, run Leopard without having to build a modified DVD. Chameleon Since the early developer builds of Mac OS X v10.6, members of the OSx86 community had been booting the new operating system using yet another bootloader called PC EFI provided by Russian hacker Netkas or the bootloader of the Voodoo team's Chameleon. Chameleon is based on David Elliot's Boot-132. The bootloader supports ACPI, SMBIOS, graphics, ethernet, and some other injections. It allows to boot up macOS on non-Macintosh hardware. Chameleon supports a lot of AMD as well as Nvidia graphics cards. There are a lot of forks of it by different developers; the latest version upstream is 2.2 from 2014. Clover Clover is a GUI bootloader for multiple operating systems that supports either UEFI or the legacy BIOS mode. To support booting EFI code, one of the two methods are conventionally taken: either Elliot's FakeEFI was used, or an actual open-source EFI system based on Intel's TianoCore called DUET (Developer's UEFI Emulation) was flashed into the motherboard. However, modern, non-Apple EFI firmware as well as Duet cannot directly load macOS due to various incompatibilities, mainly around the HFS+ file system but also due to the quirks of individual vendors. One more step was needed to load macOS systems: an EFI application to rectify these problems and bridge the gap. Beginning in March 2011, Slice discussed his idea with other community members, resulting in the development of a bootloader that can do both: emulate an EFI firmware of one's choice or use a Real UEFI firmware to boot Mac OS X. It contains EFI applications and drivers for correctly reading an HFS+ disk and patching EFI tables to prepare the system for starting macOS. As of 2020, it is actively maintained. Ozmosis Ozmosis is a UEFI DXE bootloader for Z77MX-QUO-AOS, developed by QUO Computer Inc. that is defunct in late 2010s. It offers to run macOS through motherboard’s UEFI rom, and no need additional drive space for bootloader. OpenCore OpenCore, started in 2019, is another bootloader developed to run macOS on UEFI or BIOS systems as well as old Mac devices that are no longer supported. Compared to Clover, it is said to provide overall better patching and emulation as well as a faster boot time. The project has also taken over the development of some patches, meaning future versions may only work with OpenCore. Live DVD In March 2007, the OSx86 community made some significant progress with the development of a Live DVD. The Live DVD allows booting to a working system with Mac OS X v10.4.8. On January 2, 2009, InsanelyMac's Live DVD team published a new method by which a Mac OS X v10.5.x Live DVD could be produced, allowing users to boot a fully working macOS desktop from a DVD or USB flash drive. The method was more reliable than previous methods because it manipulated Apple's existing Netboot and Imageboot functionalities and behaved as if the system were running off a network disk. It was easier to produce; requiring only a single script to be added to an existing installation. Distributions of the live DVD have been made since its inception. Since then, it is notable that this method has been shown to work on normal Apple Mac hardware. Virtual machine It is possible to run macOS as a virtual machine inside other operating systems installed on standard PC hardware by using virtualization software such as Oracle's VirtualBox (though this is not officially supported by Oracle). It is also possible to install macOS on Windows and Linux versions of VMware software through the use of patches, even though the company states that running macOS is supported for VMware running on only Apple computers in compliance with Apple's licensing policies. macOS on a virtual machine is typically very slow due to the operating system's heavy use of hardware video acceleration, which macOS does not support when using the virtual video devices typically used by virtual machine software. A work around is to attach a physical GPU to a virtual machine, however this requires a macOS supported GPU in the system that is not in use by the host operating system. See also Macintosh clone - About clones and emulators of various Macintosh models List of computer system emulators - a list of Macintosh and other computer system emulators Mac transition to Intel processors Star Trek project References MacOS

Operating System (OS)

TOPS-10 TOPS-10 System (Timesharing / Total Operating System-10) is a discontinued operating system from Digital Equipment Corporation (DEC) for the PDP-10 (or DECsystem-10) mainframe computer family. Launched in 1967, TOPS-10 evolved from the earlier "Monitor" software for the PDP-6 and PDP-10 computers; this was renamed to TOPS-10 in 1970. Overview TOPS-10 supported shared memory and allowed the development of one of the first true multiplayer computer games. The game, called DECWAR, was a text-oriented Star Trek type game. Users at terminals typed in commands and fought each other in real time. TOPS-10 was also the home of the original Multi User Dungeon, MUD, the fore runner to today's MMORPGs. Another groundbreaking application was called FORUM. This application was perhaps the first so-called CB Simulator that allowed users to converse with one another in what is now known as a chat room. This application showed the potential of multi-user communication and led to the development of CompuServe's chat application. TOPS-10 had a very robust application programming interface (API) that used a mechanism called a UUO or Unimplemented User Operation. UUOs implemented operating system calls in a way that made them look like machine instructions. The Monitor Call API was very much ahead of its time, like most of the operating system, and made system programming on DECsystem-10s simple and powerful. The TOPS-10 scheduler supported prioritized run queues, and appended a process onto a queue depending on its priority. The system also included User file and Device independence. Commands The following list of commands are supported by TOPS-10. ASSIGN ATTACH BACKSPACE BACKUP CCONTINUE COMPILE CONTINUE COPY CORE CPUNCH CREATE CREDIR CREF CSTART D(eposit) DAYTIME DCORE DDT DEASSIGN DEBUG DELETE DETACH DIRECTORY DISABLE DISMOUNT DSK DUMP E(xamine) EDIT ENABLE EOF EXECUTE FILCOM FILE FINISH FUDGE GET GLOB HALT HELP INITIA JCONTINUE KJOB LABEL LIST LOAD LOCATE LOGIN MAKE MERGE MIC MOUNT NETWORK NODE NSAVE NSSAVE OPSER PJOB PLEASE PLOT PRESERVE PRINT PROTECT PUNCH QUEUE QUOLST R REASSIGN REATTACH REENTER RENAME RESOURCES REWIND RUN SAVE SSAVE SCHED SEND SET SKIP START SUBMIT SYSTAT TECO TIME TPUNCH TYPE UNLOAD USESTAT VERSION WHERE ZERO History Release history The PDP-6 Monitor software was first released in 1964. Support for the PDP-10's KA10 processor was added to the Monitor in release 2.18 in 1967. The TOPS-10 name was first used in 1970 for release 5.01. Release 6.01 (May 1974) was the first TOPS-10 to implement virtual memory (demand paging), enabling programs larger than physical memory to be run. From release 7.00 onwards, symmetrical multiprocessing was available (as opposed to the master/slave arrangement used before). The final release of TOPS-10 was 7.04 in 1988. TOPS-10 today Hobbyists are now entitled to set up and use TOPS-10 under a Hobbyist's License. The easiest way for the hobbyist to run TOPS-10 is to acquire a suitable emulator and an operating system image. TOPS-10 may also be generated from archived original distribution "tapes". Paul Allen maintained several publicly accessible historic computer systems, including a DECsystem-2065 running TOPS-10. Software Implemented programming languages The TOPS-10 assembler, MACRO-10, was bundled with the TOPS-10 distribution. The following programming languages were implemented on TOPS-10 as layered products: ALGOL, as ALGOL-10 v10B, a compiler used for general computing APL, as APL-SF V2, an interpreter used for mathematical modelling BASIC, as BASIC-10 v17F, an interpreter used for general computing BLISS, as BLISS-10 and BLISS-36, compilers used for systems programming COBOL, as COBOL-68 and COBOL-74, compilers used for business computing Fortran, as FORTRAN-10 v11, a compiler used for numerical computing The following programming languages were implemented on TOPS-10 as contributions from DECUS members: FOCAL, as FOCAL-10 Forth, a threaded interpreted language IMP72 Lisp, an interpreter used for AI programming Pascal, a compiler used for computing education PILOT SAM76 Simula, a compiler used for modeling SNOBOL, an interpreter used for string processing BCPL, a compiler implemented by Essex University Implemented user utilities The following major user utilities were implemented on TOPS-10: RMS (Records Management Services) IQL (Interactive Query language) DBMS-10 (CODASYL Database Management System) Notable games implemented on TOPS-10 ADVENT DECWAR, as noted above FORUM, as noted above HAUNT, an early role-playing game Mac Hack, a chess program by Richard Greenblatt MUD Legacy MS-DOS was heavily influenced by TOPS-10. Identical elements include three characters long file extensions, several standard extensions (for eg. EXE, TXT), the asterisk () as a wildcard, the usage of the slash () as a switch separator and more. See also PDP-10 TOPS-20 WAITS References DEC operating systems Time-sharing operating systems 1964 software

Operating System (OS)

DR-DOS DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-DOS (which were the same product sold under different names). DR-DOS was developed by Gary A. Kildall's Digital Research and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. As ownership changed, various later versions were produced with names including Novell DOS and Caldera OpenDOS. History Origins in CP/M Digital Research's original CP/M for the 8-bit Intel 8080- and Z-80-based systems spawned numerous spin-off versions, most notably CP/M-86 for the Intel 8086/8088 family of processors. Although CP/M had dominated the market since the mid-1970s, and was shipped with the vast majority of non-proprietary-architecture personal computers, the IBM PC in 1981 brought the beginning of what was eventually to be a massive change. IBM originally approached Digital Research in 1980, seeking an x86 version of CP/M. However, there were disagreements over the contract, and IBM withdrew. Instead, a deal was struck with Microsoft, who purchased another operating system, 86-DOS, from Seattle Computer Products (SCP). This became Microsoft MS-DOS and IBM PC DOS. 86-DOS's command structure and application programming interface imitated that of CP/M 2.2 (with BDOS 2.2). Digital Research threatened legal action, claiming PC DOS/MS-DOS to be too similar to CP/M. In early 1982, IBM settled by agreeing to sell Digital Research's x86 version of CP/M, CP/M-86, alongside PC DOS. However, PC DOS sold for while CP/M-86 had a $240 price tag. The proportion of PC buyers prepared to spend six times as much to buy CP/M-86 was very small, and the availability of compatible application software, at first decisively in Digital Research's favor, was only temporary. Digital Research fought a long losing battle to promote CP/M-86 and its multi-tasking multi-user successors MP/M-86 and Concurrent CP/M-86, and eventually decided that they could not beat the Microsoft-IBM lead in application software availability, so they modified Concurrent CP/M-86 to allow it to run the same applications as MS-DOS and PC DOS. This was shown publicly in December 1983 and shipped in March 1984 as Concurrent DOS 3.1 (a.k.a. CDOS with BDOS 3.1) to hardware vendors. While Concurrent DOS continued to evolve in various flavours over the years to eventually become Multiuser DOS and REAL/32, it was not specifically tailored for the desktop market and too expensive for single-user applications. Therefore, over time two attempts were made to sideline the product: In 1985, Digital Research developed DOS Plus 1.0 to 2.1, a stripped-down and modified single-user derivative of Concurrent DOS 4.1 and 5.0, which ran applications for both platforms, and allowed switching between several tasks as did the original CP/M-86. Its DOS compatibility was limited, and Digital Research made another attempt, this time a native DOS system. This new disk operating system was launched in 1988 as DR DOS. Although DRI was based in Pacific Grove and later in Monterey, California, USA, the work on DOS Plus started in Newbury, Berkshire in the UK, where Digital Research Europe had its OEM Support Group located since 1983. Beginning in 1986, most of the operating system work on Concurrent DOS 386 and XM, Multiuser DOS, DR DOS and PalmDOS was done in Digital Research's European Development Centre (EDC) in Hungerford, Berkshire. Later on some work was also done by Digital Research GmbH in Munich, Germany. First DR DOS version As requested by several OEMs, Digital Research started a plan to develop a new DOS operating system addressing the shortcomings left by MS-DOS in 1987. Of particular importance was a million dollar deal with Kazuhiko "Kay" Nishi of ASCII Corporation, who had previously been instrumental in opening the Japanese OEM market for Microsoft. The first DR DOS version was released on 28 May 1988. Version numbers were chosen to reflect features relative to MS-DOS; the first version promoted to the public was DR DOS 3.31, which offered features comparable to Compaq MS-DOS 3.31 with large disk support (FAT16B a.k.a. "BIGDOS"). DR DOS 3.31 reported itself as "IBM PC DOS 3.31", while the internal BDOS (Basic Disk Operating System) kernel version was reported as 6.0, single-user nature, reflecting its origin as derivative of Concurrent DOS 6.0 with the multitasking and multiuser capabilities as well as CP/M API support stripped out and the XIOS replaced by an IBM-compatible DOS-BIOS. The system files were named DRBIOS.SYS (for the DOS-BIOS) and DRBDOS.SYS (for the BDOS kernel), the disk OEM label used was "DIGITAL␠". DR DOS offered some extended command line tools with command line help, verbose error messages, sophisticated command line history and editing (HISTORY directive) as well as support for file and directory passwords built right into the kernel. It was also cheaper to license than MS-DOS, and was ROMable right from the start. The ROMed version of DR DOS was also named ROS (ROM Operating System). DRI was approached by a number of PC manufacturers who were interested in a third-party DOS, which prompted several updates to the system. At this time, MS-DOS was only available to OEMs bundled with hardware. Consequently, DR DOS achieved some immediate success when it became possible for consumers to buy it through normal retail channels beginning with version 3.4x. Known versions are DR DOS 3.31 (BDOS 6.0, June 1988, OEM only), 3.32 (BDOS 6.0, 17 August 1988, OEM only), 3.33 (BDOS 6.0, 1 September 1988, OEM only), 3.34 (BDOS 6.0, OEM only), 3.35 (BDOS 6.0, 21 October 1988, OEM only), 3.40 (BDOS 6.0, 25 January 1989), 3.41 (BDOS 6.3, June 1989, OEM and retail). Like MS-DOS, most of them were produced in several variants for different hardware. While most OEMs kept the DR DOS name designation, 2001 Sales, Inc. marketed it under the name EZ-DOS 3.41 (also known as EZ-DOS 4.1). DR DOS 5.0 DR DOS version 5.0 (code-named "Leopard") was released in May 1990, still reporting itself as "PC DOS 3.31" for compatibility purposes, but internally indicating a single-user BDOS 6.4 kernel. (Version 4 was skipped to avoid being associated with the relatively unpopular MS-DOS 4.0.) This introduced ViewMAX, a GEM-based GUI file management shell. ViewMAX's startup screen would present the slogan "Digital Research - We make computers work". DR DOS 5.0 also introduced the patented BatteryMAX power management system, bundled disk-caching software (DRCACHE), a remote file transfer tool (FILELINK), a cursor shape configuration utility (CURSOR), and offered a vastly improved memory management system (MemoryMAX). For compatibility purposes, the DR DOS 5.0 system files were now named IBMBIO.COM (for the DOS-BIOS) and IBMDOS.COM (for the BDOS kernel) and due to the advanced loader in the boot sector could be physically stored anywhere on disk. The OEM label in the boot sectors was changed to "IBM␠␠3.3". DR DOS 5.0 was the first DOS to include load-high capabilities. The kernel and data structures such as disk buffers could be relocated in the High Memory Area (HMA), the first 64 KB of extended memory which are accessible in real mode. This freed up the equivalent amount of critical "base" or conventional memory, the first 640 KB of the PC's RAM – the area in which all DOS applications run. Additionally, on Intel 80386 machines, DR DOS's EMS memory manager allowed the operating system to load DOS device drivers into upper memory blocks, further freeing base memory. DR DOS 5.0 was the first DOS to integrate such functionality into the base OS (loading device drivers into upper memory blocks was already possible using third-party software like QEMM). This allowed it, on 286 systems with supported chipsets and on 386 systems, to provide significantly more free conventional memory than any other DOS. Once drivers for a mouse, multimedia hardware and a network stack were loaded, an MS-DOS/PC DOS machine typically might only have had 300 to 400 KB of free conventional memory – too little to run much late-1980s software. In contrast to this, DR DOS 5.0, with a little manual tweaking, could load all this and still keep all of its conventional memory free – allowing for some necessary DOS data structures, as much as 620 KB out of the 640 KB. With MEMMAX +V, the conventional memory region could even be extended into unused portions of the graphics adapter card typically providing another 64 to 96 KB more free DOS memory. Because DR DOS left so much conventional memory available, some old programs utilizing certain address wrapping techniques failed to run properly as they were now loaded unexpectedly (or, under MS-DOS, "impossibly") low in memory – inside the first 64 KB segment (known as "low memory"). Therefore, DR DOS 5.0's new MEMMAX -L command worked around this by pre-allocating a chunk of memory at the start of the memory map in order for programs to load above this barrier (but with less usable conventional memory then). By default, MEMMAX was configured for +L, so that applications could take advantage of the extra memory. DR DOS 6.0 / Competition from Microsoft Faced with substantial competition in the DOS arena, Microsoft responded with an announcement of a yet-to-be released MS-DOS 5.0 in May 1990. This would be released in June 1991 and include similar advanced features to those of DR DOS. It included matches of the DR's enhancements in memory management. Almost immediately in September 1991, Digital Research responded with DR DOS 6.0, code-named "Buxton". DR DOS 6.0, while already at BDOS level 6.7 internally, would still report itself as "IBM PC DOS 3.31" to normal DOS applications for compatibility purposes. This bundled in SuperStor on-the-fly disk compression, to maximize available hard disk space, and file deletion tracking and undelete functionality by Roger A. Gross. DR DOS 6.0 also included a task-switcher named TASKMAX with support for the industry-standard task-switching API to run multiple applications at the same time. In contrast to Digital Research's Multiuser DOS (successor of Concurrent DOS in the multi-user products line), which would run DOS applications in pre-emptively multitasked virtual DOS machines, the DR DOS 6.0 task switcher would freeze background applications until brought back into the foreground. While it ran on x86-machines, it was able to swap to XMS memory on 286+ machines. TASKMAX did support some Copy & Paste facility between applications. Via the task-switcher API, graphical user interfaces such as ViewMAX or PC/GEOS could register as the task manager menu and thereby replace the TASKMAX text mode menu, so that users could switch between tasks from within a GUI. Microsoft responded with MS-DOS 6.0, which again matched some features of DR DOS 6.0. In December 1991, a pre-release version of Windows 3.1 was found to return a non-fatal error message if it detected a non-Microsoft DOS. This check came to be known as the AARD code. It was a simple matter for Digital Research to patch DR DOS 6.0 to circumvent the AARD code 'authenticity check' in the Windows 3.1 beta by rearranging the order of two internal tables in memory (with no changes in functionality), and the patched version, named "business update", was on the streets within six weeks of the release of Windows 3.1. With the detection code disabled, Windows ran perfectly under DR DOS and its successor Novell DOS. The code was present but disabled in the released version of Windows 3.1. In July 1992, Digital Research Japan released DR DOS 6.0/V, a Japanese DOS/V compatible version of DR DOS 6.0. A Korean version appears to have been available as well. PalmDOS In 1992 Digital Research, still under its old name but already bought by Novell in July 1991, also embarked on a spin-off product code-named "Merlin" and later released as NetWare PalmDOS 1, which, as its name implies, was a very resource-light DR DOS 6.0 derivative aimed at the emerging Palmtop/PDA market. PalmDOS was the first operating system in the family to support the new BDOS 7.0 kernel with native DOS compatible internal data structures instead of emulations thereof. Replacing the DOS emulation on top of a CP/M kernel by a true DOS compatible kernel helped a lot in improving compatibility with some applications using some of DOS' internal data structures and also was the key in reducing the resident size of the kernel code even further—a particular requirement for the PDA market. On the other hand, introducing a genuine Current Directory Structure (CDS) imposed a limit on the depth of working directories down to 66 characters (as in MS-DOS/PC DOS), whereas previous issues of DR DOS had no such limitation due to their internal organization of directories as relative links to parent directories instead of as absolute paths. PalmDOS still reported itself as "PC DOS 3.31" to applications in order to keep the kernel small and not run into compatibility problems with Windows, which would expect the DOSMGR API to be implemented for any DOS version since 5.0. As well as a ROM-executing kernel, PalmDOS had palmtop-type support for features such as PCMCIA PC Cards (with DPMS support), power management (BatteryMAX and the $IDLE$ device driver with its patented dynamic idle detection by Gross and John P. Constant), MINIMAX task switcher support for PIM (Personal Information Modules) applications stored and executed from ROM via XIP (Execute-In-Place), etc. The PCMCIA stack for PalmDOS was partially written by Ian H. S. Cullimore. Novell DOS 7 / Contribution by Novell Novell DOS was Novell Corporation's name for DR DOS during the period when Novell sold DR DOS, after the acquisition of Digital Research in 1991. Regarding features and performance, it was typically at least one release ahead of MS-DOS. In 1993, PC DOS 6.1, MS-DOS 6.2 and PC DOS 6.3 were trumped by Novell's . Novell CEO Robert J. Frankenberg's strategy included "major trimming", selling off products like transactional database Btrieve and killing others such as Novell DOS and WordPerfect's multimedia Main Street children's titles. Novell licensed technology from Stac Electronics for use in Novell DOS and its Network operating system, NetWare. Novell sold the product line off to Caldera on 23 July 1996, after it approached Novell looking for a DOS operating system to bundle with its OpenLinux distribution. Marc Perkel claimed to have had inspired Novell in February 1991 to buy Digital Research and develop something he envisioned as "NovOS". Novell had actually bought Digital Research in July 1991 with a view to using DR's product line as a lever in their comprehensive strategy to break the Microsoft monopoly. (This was part of a massive and ultimately disastrous spending spree for Novell: they bought WordPerfect Corporation at about the same time, some of Borland's products, and invested heavily in Unix as well.) The planned "DR DOS 7.0", internally named "Panther", intended to trump Microsoft's troubled MS-DOS 6.0, was repeatedly delayed, while Novell was working on an optionally loadable Unix-like multi-user security extension (with, if loaded, file commands like BACKUP, DELPURGE, MOVE, TOUCH, TREE, UNDELETE, XATTRIB, XCOPY, XDEL and XDIR supporting an otherwise disabled /U:name command line option to select specific users or groups, compatible with Multiuser DOS) and two new graphical user interfaces (ViewMAX 3, a derivative of GEM, and "Star Trek", a true port of Apple's System 7.1 to run under the new DR DOS multitasker named "Vladivar"). When DR DOS eventually arrived in December 1993 (with localized versions released in March 1994), renamed Novell DOS 7 (a.k.a. "NWDOS"), and without these three components, it was a disappointment to some. It was larger and lacked some finishing touches, but was nevertheless seen as best DOS by many industry experts. In Germany, Novell DOS 7 was aggressively marketed with the slogan "" (Don't trust any DOS below 7) in the press and with free demo floppies in computer magazines. The campaign aimed at 20% of the DOS market and resulted in about 1.5 million copies sold until February 1994 and more than 3000 dealers interested to carry the product. Novell DOS 7 was available through various OEMs, a dedicated mail order shop and authorized dealers. A major functional addition was Novell's second attempt at a peer-to-peer networking system, Personal NetWare (PNW). This was better than its predecessor, NetWare Lite (NWL), but it was incompatible with Microsoft's networking system, now growing popular with support in Windows for Workgroups, OS/2, and Windows NT. A considerable amount of manual configuration was needed to get both to co-exist on the same PC, and Personal NetWare never achieved much success. Since Novell DOS 7 implemented the DOSMGR API and internal data structures had been updated, its BDOS 7.2 kernel could report with a DOS version of 6.0 and OEM ID "IBM" without risking compatibility problems with Windows. Most tools would report this as "PC DOS 6.1", because IBM PC DOS 6.1 also reported as DOS 6.0 to applications. Novell DOS 7 introduced much advanced memory management including new support for DPMI (DOS Protected Mode Interface) and DPMS (DOS Protected Mode Services) as well as more flexible loadhigh options. It also introduced support for "true" pre-emptive multitasking of multiple DOS applications in virtual DOS machines (VDM), a component originally named MultiMAX. This was similar to Multiuser DOS, but now on the basis of a natively DOS compatible environment, similar to Windows 386 Enhanced Mode, but without a GUI. By default, the bundled TASKMGR would behave similar to the former DR DOS 6.0 TASKMAX. However, if EMM386 was loaded with the option /MULTI, EMM386 would load a natively 32-bit 386 Protected Mode operating system core providing API support for pre-emptive multitasking, multi-threading, hardware virtualization and domain management of virtual DOS machines. This API could be used by DR DOS-aware applications. If TASKMGR was run later on, it would use this API to instance the current 16-bit DOS system environment, create virtual DOS machines and run applications in them instead of using its own Real Mode task-switcher support. The multitasker was compatible with Windows, so that tasks started before launching Windows could be seen as tasks under Windows as well. Novell DOS 7 and Personal NetWare 1.0 also shipped with NetWars, a network-enabled 3D arcade game. Novell DOS 7 and Personal NetWare required several bug-fix releases (D70xyy with x=language, yy=number) and were not completely stable when the next development occurred. With beta versions of Microsoft's "Chicago" (what would later become Windows 95) in sight, Novell wound down further development on Novell DOS 7 in September 1994 and stopped maintenance in January 1996 after more than 15 updates. After Novell When Caldera approached Novell looking for a DOS operating system to bundle with their OpenLinux distribution, Novell sold the product line off to Caldera on 23 July 1996, by which time it was of little commercial value to them. Between the Caldera-owned DR-DOS and competition from IBM's PC DOS 6.3, Microsoft moved to make it impossible to use or buy the subsequent Windows version, Windows 95, with any DOS product other than their own. Claimed by them to be a purely technical change, this was later to be the subject of a major lawsuit brought in Salt Lake City by Caldera with the help of the Canopy Group. Microsoft lawyers tried repeatedly to have the case dismissed but without success. Immediately after the completion of the pre-trial deposition stage (where the parties list the evidence they intend to present), there was an out-of-court settlement on 7 January 2000 for an undisclosed sum. This was revealed in November 2009 to be $280 million. In August 1996, the US-based Caldera, Inc. was approached by Roger A. Gross, one of the original DR-DOS engineers, with a proposal to restart DR-DOS development and to make Windows 95 run on DR-DOS which would help the court case. Following a meeting in September 1996 in Lindon, Utah, USA, between Gross, Ransom H. Love, Bryan Wayne Sparks and Raymond John Noorda, Gross was hired and tasked to set up a new subsidiary in the UK. On 10 September 1996, Caldera announced the coming release of OpenDOS (COD) and their intent to also release the source code to the system, and Caldera UK Ltd. was incorporated on 20 September 1996. Gross hired some of the original developers of the operating system from the Novell EDC as well as some new talents to continue work on the operating system in a converted barn at the periphery of Andover, Hampshire, UK, nearby the former Digital Research and Novell EDC. Besides other improvements and enhancements all over the system, a string of new key features were added subsequently over the course of the next two years, including a TCP/IP stack (derived from LAN WorkPlace for DOS / NetWare Mobile), a graphical 32-bit DOS Protected Mode HTML 3.2 web-browser DR-WebSpyder (originally based on source code from the Arachne web browser by Michal Polák) with LAN and modem dialup, a POSIX Pthreads extension to the multi-tasker by Andy T. Wightman, long filename (LONGNAME) support by Edward N. Hill, Jr., as well as LBA and FAT32 support (DRFAT32) by Matthias R. Paul. Gross also hired Andrew Schulman (who had been, with Geoff Chappell, instrumental in identifying the AARD code in 1992) to work as a consultant and, in Andover, assist Paul in his work on "WinGlue", a secret project to create a version of DR-DOS compatible with Windows 95, 98 and 98 SE and replace its MS-DOS 7.xx component. This was demonstrated at CeBIT in March 1998, and later, in a small team, developed into "WinBolt", both versions of DR-DOS, which remained unreleased , but played an important role in the court case. Caldera UK officially released Caldera OpenDOS 7.01 on 3 February 1997, but this version was just Novell DOS 7 update 10 (as of December 1994) compiled only with the necessary adaptations to incorporate the new name in display messages as well as in environment variables and file names. It was missing a year's worth of patches which had been developed for the Novell DOS updates 11 (January 1995) to 15.2 (January 1996). This was due to parts of the Novell DOS sources having been lost at Novell meanwhile. Consequently, this version still reported an internal BDOS version of 7.2, identical to Novell DOS 7. The new suite also lacked the SETFIFO command, which had been added with one of the Novell DOS updates, as well as Fifth Generation's Search&Destroy virus scanner and FastBack Plus 2.0 utility, which previously came bundled with Novell DOS. Instead it came bundled with a newer version of PNUNPACK and brought a much advanced version of NetWars. Parts of OpenDOS 7.01 were released as open source in form of the M.R.S. kit (for Machine Readable Sources) in May 1997, but with license terms mostly incompatible with existing open-source licenses. The source was then closed again as Gross felt this would undermine the commercial aspirations of the system. After beta releases in September and November 1997, the next official release came in December 1997, with the name changed to Caldera DR-OpenDOS 7.02, soon followed by a further release in March 1998, when the DR-DOS name returned as Caldera DR-DOS 7.02, now for the first time written with a hyphen. Version 7.02 (now reporting itself as BDOS 7.3) incorporated improved BIOS and BDOS issues, developed by Paul, adding many new boot and configuration options, integrating many compatibility enhancements, bug-fixes and optimizations for size and speed, and re-implementing all fixes of the missing Novell DOS updates. The BIOS improved the coexistence of DR-DOS with Windows 9x and its support for third-party disk compression drivers such as Microsoft's DriveSpace. It introduced a diagnostics mode (activated by Scroll Lock), integrated debugger support (with DEBUG=ON and a debugger loaded before or from within CONFIG.SYS) and more flexible CONFIG.SYS tracing capabilities via the /// hotkeys and the TRACE and TIMEOUT commands, thereby also improving the integration of alternative command line shells such as 4DOS. Together with LOADER, SYS /DR:ext and the CHAIN directive, it brought enhanced multi-configuration support for DR/D/CONFIG.ext files and came with enhancements to the BASIC-like CONFIG.SYS language for more powerful boot menus, convenient user interaction and programmatical acting upon conditions (CPU386), return codes and error levels (ERROR, ONERROR). It also allowed to change the SCROLLOCK, CAPSLOCK, INSERT and VERIFY settings as well as the SWITCHAR, YESCHAR, NOCHAR and RESUMECHAR characters. Various behavioural details could be controlled with new parameters /Q (Quiet), /L (Lowercase), /Y (Yes) and /S (Switch) for SWITCHES. Further, it provided optional support for a LPT4: device and allowed to configure the built-in COMx: and LPTx: devices as well as to change the PRN: and AUX: defaults. The handling of environment variables in CONFIG.SYS was improved and new load-high facilities included such as the HIFILES/FILESHIGH and HIFCBS/FCBSHIGH options to relocate file handles and FCB structures into UMBs, which typically gave between 1 and 4 KB (and up to 15 KB) more free conventional memory compared to previous versions, or the HISHELL/SHELLHIGH SIZE directive to control the pre-allocation of HMA memory for COMMAND.COM, which helped to avoid memory fragmentation and thereby typically gave between 5 and 8 KB more continuous HMA memory for HMA-capable third-party drivers to work with in conjunction with third-party command line shells, which could not load into the HMA as COMMAND.COM with its /MH option. At a reduced memory footprint version 7.02 also brought an enhanced NLS 4.xx sub-system by Paul to allow multiple, distributed and possibly user-configured COUNTRY.SYS files to be used by the system at the same time in a hierarchical model. This also gave dynamic parser support for MS-DOS/PC DOS COUNTRY.SYS file formats in addition to DR-DOS' own COUNTRY.SYS formats, and it introduced support for the ISO 8601 international date format (including automatic detection) and the then-new Euro currency. Some DR-DOS files such as IBMBIO.COM, IBMDOS.COM and COUNTRY.SYS carried misleading file extensions for compatibility reasons; with DR-DOS 7.02 they were enhanced to incorporate a fat binary-style safety feature devised by Paul so that they would exit gracefully when called inappropriately. DR-DOS 7.02 was fully Year 2000 compliant and provided special support to work with buggy system BIOSes. It also came with an updated FDISK, which could partition and format FAT32 volumes (but not yet work with LBA). The sources of the Novell patches for the external tools and drivers had meanwhile been found in Germany and could thus be retro-fitted into the system as well, so that DR-DOS 7.02 finally not only caught up with Novell DOS 7, but was a true step forward. The release was followed by various updates in June, August and September 1998. The updated internal BDOS version number introduced a new problem: some legacy third-party applications with special support for Novell DOS, which were no longer being updated, stopped working. SETVER already allowed Novell DOS to disguise itself as DOS versions by file name and globally and, specifying a magic sub-version of 255, it would even disable its own internal BDOS version check in order to cope with programs specifically probing for "DR-DOS". The modified kernel and SETVER driver by Paul would, in an hierarchical model, also support load paths in order to distinguish between multiple executables of the same file name, and it introduced an extended mode, in which SETVER could not only fake DOS versions, but also BDOS kernel versions. Sub-versions of 128 to 255 would be reported as DOS sub-versions 0 to 127 to applications, but with the BDOS version check disabled, while sub-versions 100 to 127 could be used to fake different BDOS versions, whereas the DOS revision number (typically set to 0 in a static, pre-boot patchable data structure) would be taken as the reported sub-version instead, so that SETVER /G /X 6.114 would allow versions of DR-DOS since 7.02 to still report themselves as a "DOS 6.0" and with a faked BDOS version 7.2 (114 decimal = 72 hexadecimal), thereby masquerading as Novell DOS 7 / OpenDOS 7.01. While otherwise beneficial, the new HIFILES triggered a compatibility problem in the DOS-UP feature of the third-party memory manager QEMM 8, which was hard-wired to expect a chunk of five handle structures in conventional memory under DR-DOS (as with previous versions up to 7.01), whereas version 7.02 by design left eight handles in low memory when loading high files in order to maintain full compatibility with older versions of Windows 3.xx. Compatibility with Windows for Workgroups 3.11 had not been affected by this. A maintenance fix was devised to patch a single byte in IBMBIO.COM in order to switch the behaviour and optionally re-invoke the old chunking. This freed some 150 bytes of conventional memory and enabled full compatibility with DOS-UP, but at the same time broke compatibility with older versions of Windows 3.xx when using the HIFILES feature, and vice versa. The patch named IBMBIO85.SCR continued to work with newer versions of DR-DOS. In August 1998 the US-based Caldera, Inc. created two new subsidiaries, Caldera Systems, Inc. for the Linux business, and Caldera Thin Clients, Inc. for the embedded and thin-client market. Another version, DR-DOS 7.03 (still with BDOS 7.3 and reporting itself to applications as "PC DOS 6.0" for compatibility purposes), was pre-released at Christmas 1998 and then officially released on 6 January 1999 by Caldera UK. It came with significantly improved memory managers (in particular enhanced DPMI support in conjunction with the multitasker) and other enhancements, such as added DEVLOAD and DRMOUSE utilities, but a changed OEM label in the boot sector of volumes formatted under DR-DOS could also cause problems under other operating systems (which can be circumvented by NOVOLTRK). DR-DOS 7.03 would become the last version of DR-DOS also tailored for desktop use. Caldera, Inc. wanted to relocate the DR-DOS business into the US and closed the highly successful UK operation in February 1999 after Gross resigned and set up iCentrix to develop the MarioNet split web browser. Development was then moved into the US (which never worked out due to a total lack of expertise in this field at Caldera US), and the DR-DOS line fell to its branch company, Caldera Thin Clients, which was renamed Lineo, Inc. on 20 July 1999. DR-WebSpyder was renamed Embrowser and was said to be ported to Linux. Lineo re-released DR-DOS 7.03 in June and September 1999, still branded as "Caldera DR-DOS" and without any changes, but otherwise focussed on Linux for embedded systems, based on a stripped-down version of OpenLinux named Embedix. Among the latest and independently developed versions of DR-DOS were OEM DR-DOS 7.04 (as of 19 August 1999) and 7.05 (as of 30 November 1999), still branded as "Caldera DR-DOS". These were variants of the system consisting only of the kernel and command shell. With a specialized native implementation of FAT32 and large hard disk support they could be found bundled with Ontrack's Easy Recovery 5 in 2000, replacing the dynamically-loadable DRFAT32 redirector driver, which still came with Easy Recovery 4. They were also used for Seagate Technology's SeaTools and the CD imaging software Nero Burning ROM. While still reporting a BDOS 7.3 internally, these were the first versions to report themselves as "PC DOS 7.10" to applications in order to indicate integrated FAT32 support. Designed to be mostly backwards-compatible, the DR-DOS 7.04/7.05 IBMBIO.COM could be combined with the DR-DOS 7.03 IBMDOS.COM in order to give the desktop-approved DR-DOS 7.03 kernel LBA capabilities and work with drives larger than 8 GB. For specific OEM requirements, DR-DOS 7.06 (as of 14 December 1999) by Wightman combined the kernel files into a single binary executable, so that, similar to IO.SYS of Windows 98, it could be booted by MS-DOS 7.10 boot sectors (but no longer by DR-DOS boot sectors). DR-DOS 7.07 (with BDOS 7.4/7.7) by Paul introduced new bootstrap loaders and updated disk tools in order to combine support for CHS and LBA disk access, the FAT12, FAT16 and FAT32 file systems, and the differing bootstrapping conventions of DR-DOS, PC DOS, MS-DOS, Windows, REAL/32 and LOADER into a single NEWLDR MBR and boot sector, so that the code would continue to load any version of DR-DOS down to 3.31 (and since DR-DOS 7.04 also with FAT32 support), but could also be used to launch the PC DOS or MS-DOS system files, including those of Windows 9x and PC DOS 7.10. At the same time the kernel could not only be booted by the new sectors, but also by any previously DR-DOS formatted disks, as well as off disks with existing PC DOS or MS-DOS boot sectors and a variety of other boot-loaders, thereby easing the coexistence and setup of multi-boot scenarios in conjunction with other operating systems. Later versions In 2002, Lineo was bought out, and some of Lineo's former managers purchased the name and formed a new company, DRDOS, Inc. dba DeviceLogics L.L.C. They have continued to sell DR-DOS for use in embedded systems. DR-DOS 8.0 was released on 30 March 2004 featuring FAT32 and large disk support, the ability to boot from ROM or Flash, multitasking and a DPMI memory manager. This version was based on the kernel from version 7.03. The company later released DR-DOS 8.1 (with better FAT32 support) in autumn 2005. This version was instead based on OpenDOS 7.01.xx. DR-DOS 8.1 was withdrawn for GPL violations (see Controversies). Aside from selling copies of the operating system, the DRDOS, Inc. website lists a buyout option for DR-DOS; the asking price is . The OpenDOS 7.01 source code was a base for The DR-DOS/OpenDOS Enhancement Project, set up in July 2002 in an attempt to bring the functionality of DR-DOS up to parity with modern PC non-Windows operating systems. The project's added native support for large disks (LBA) and the FAT32 file system, and several other enhancements, including improved memory management and support for the new FAT32+ file system extension which allows files of up to 256 GB in size on normal FAT partitions. DR-DOS 7.01.08 was released on 21 July 2011. Controversies In October 2005, it was discovered that DR-DOS 8.1 included several utilities from FreeDOS as well as other sources, and that the kernel was an outdated version of the Enhanced DR-DOS kernel. DR DOS, Inc. failed to comply with the GNU General Public License (GPL) by not crediting the FreeDOS utilities to their authors and including the source code. After complaints from FreeDOS developers (including the suggestion to provide the source code, and hence comply with the GPL), DR DOS, Inc. instead withdrew version 8.1, and also the unaffected 8.0, from its website. Commands APPEND, ASSIGN, BATCH, DBG, DELQ, ERA, ERAQ, MORE and SUBST have been among the internal commands supported since DR DOS 3.31. DR DOS 5.0 removed BATCH and added HILOAD. GOSUB, IDLE, RETURN and SWITCH were added as internal commands with DR DOS 6.0. ASSIGN and SUBST were changed to become external commands with DR DOS 6.0. ECHOERR and PAUSEERR existed as internal commands in DR DOS 6.0 (and in Multiuser DOS), but were not normally enabled. MORE remained an internal command up to including PalmDOS, but was changed to an external command with Novell DOS 7. DBG was removed with Novell DOS 7, LOADHIGH, LH and TRUENAME were added as internal commands. APPEND was still an internal command in DR DOS 6.0, but was changed to an external command with Novell DOS 7. Internal commands The following list of internal commands is supported by DR DOS 6.0: APPEND BREAK CD CHCP CHDIR CLS COPY CTTY DATE DBG DEL DELQ DIR ERA ERAQ ERASE EXIT HILOAD IDLE MD MKDIR MORE PATH PROMPT RD REN RENAME RMDIR SET TIME TYPE VER VERIFY VOL Batch processing subcommands Batch processing subcommands of DR DOS 6.0 include: ? CALL ECHO ECHOERR FOR GOSUB GOTO IF OR PAUSE PAUSEERR REM RETURN SHIFT SWITCH External commands DR DOS 6.0 supports the following external commands: ASSIGN ATTRIB BACKUP CHKDSK COMMAND COMP CURSOR DELPURGE DELWATCH DISKCOMP DISKCOPY DISKMAP DISKOPT DOSBOOK EDITOR EXE2BIN FASTOPEN FC FDISK FILELINK FIND FORMAT GRAFTABL GRAPHICS JOIN KEYB LABEL LOCK MEM MEMMAX MODE MOVE NLSFUNC PASSWORD PRINT RECOVER RENDIR REPLACE RESTORE SCRIPT SETUP SHARE SID SORT SSTOR SUBST SUPERPCK SYS TASKMAX TOUCH TREE UNDELETE UNFORMAT UNINSTAL XCOPY XDEL XDIR See also CP/M MP/M DOS Plus Multiuser DOS NetWare MarioNet split web browser Comparison of DOS operating systems Timeline of DOS operating systems AARD code General Software Embedded BIOS Notes References Further reading (501 pages) (88 pages) (11 pages) (A5 – 1 fold) (698 pages) (106 pages) External links Official website (archived snapshot as of 2018-07-05) Enhanced DR-DOS/OpenDOS Project DR-DOS 7 online manual DR-DOS Wiki Caldera (company) operating systems Novell Digital Research operating systems 1988 software Disk operating systems DOS variants Embedded operating systems Floppy disk-based operating systems Microcomputer software Microsoft criticisms and controversies Operating system distributions bootable from read-only media Proprietary operating systems ROM-based operating systems Assembly language software

Operating System (OS)

DOS XL DOS XL is a discontinued Disk Operating System (DOS) written by Paul Laughton, Mark Rose, Bill Wilkinson, and Mike Peters and published by Optimized Systems Software (OSS) for the Atari 8-bit family of home computers. It was designed to be compatible with Atari DOS which came shipped with Atari, Inc.'s disk drives, which had also been written by the same team. Description Features A direct descendant of OS/A+, DOS XL provided additional features to Atari's equipped with floppy disk drives. These included single and double density support, a command-line mode (called the command processor or CP), a menu mode (an executable loaded in memory), batch file support, and support for XL extended memory and OSS SuperCartridge banked memory. Later versions included Axlon RamDisk support, Mosaic RamDisk support, BIT-3 support and BUG/65. In addition to supporting auto-booting AUTORUN.SYS files, DOS XL's batch features provided an auto-booting batch feature. Naming a batch file to STARTUP.EXC would have it execute batch commands on startup (same as OS/A+). Unfortunately, this feature wasn't compatible with some programs (e.g. AtariWriter). Distribution DOS XL was distributed on a flippy disk. One side had the single-density version, the other had the double-density version. As more features and add-ons were included, these were placed on the double-density side only due to lack of disk space. The manual for DOS XL was a subset of OS/A+. OSS considered the manual an "addendum" to OS/A+. Over 150+ pages, it was bound at the spine, not in loose-leaf form like the OS/A+ manual. DOS XL came in two versions, 2.20 and 2.30 (2.20 users had to pay $20 to upgrade to 2.30). The last version was 2.30P. DOS XL originally sold for $30, but the price later increased to $39. File writing verify was turned off in DOS XL. This was due to OSS's own experience that resulted in faster writes with virtually no risk of errors. The command file VERIFY.COM was included to reenable writes with verify. Atari DOS 2.0S by default verified file writes to disk. Several disk drive manufacturers shipped DOS XL with their drives: Trak, Percom, Astra, Indus, Amdek, and Rana. Commands Menu Commands C - Copy Files P - Protect Files D - Duplicate Disk Q - Quit to DOS XL E - Erase Files R - Rename File F - Files on Disk S - Save Binary G - Go to Address T - To Cartridge I - Initialize Disk U - Unprotect Files L - Load Binary X - Xtended Command Intrinsic Commands @ - Begins execution of a batch file CAR - Runs Cartridge Dn: - Changes default drive DIR - Directory END - Tells DOS XL to stop batch execution (used in a batch file) ERA - Erase file(s) LOA - Load file(s) in memory NOS - NO Screen. Turns off command echo to screen PRO - Protect. Enables write-protect on file(s) REM - REMark. Used for user remarks in batch files REN - REName. Renames file(s) RUN - Jumps to run address SAV - Saves a portion of memory to disk SCR - Enables commands to be echoed to screen (for batch files) TYP - Displays ASCII or ATASCII text files to screen UNP - Turns off write-protect on file(s) Extrinsic Commands C65 CLRDSK CONFIG COPY DO DUPDBL DUPDSK INIT INITDBL MAC65 MENU NOVERIFY RS232 RS232FIX SDCOPY VERIFY BASIC Extended Commands CLOSE ENTER GET INPUT LIST LOAD NOTE OPEN POINT PRINT PUT SAVE PROTECT (XIO 35) UNPROTECT (XIO 36) RENAME (XIO 32) ERASE (XIO 33) Patch Version 2.30p was a newer version to 2.30 to fix two problems. In previous versions of DOS XL, if you initialized a disk from the menu, the disk would not boot unless the file MENU.COM was on the disk. To alleviate this problem, type Q to quit the menu. Then type INIT or INITDBL from the command processor. Note: everything on the menu can be done manually from the command processor. If you have a multidrive system and you initialized a disk in a drive other than one, when booted, the disk will always come up with the number of the drive on which it was initialized. To prevent this problem, use D1: as the destination drive. The patch for DOS XL 2.30 to make it a 2.30p: OSS Disk Newsletter Fall 1986 Product News & Info DOS XL - New-found Bugs DOS XL Bugs and Fixes BUG: The patch to convert version 2.30 to version 2.30p in our Spring 1984 newsletter didn't work. FIX: Run the following program and then use INIT with the "Write DOS.SYS Only" option to write out the patched DOS. Make sure that you don't have DOSXL.SYS (either .SUP or .XL version) active when you do this. 100 READ CNT:IF CNT=0 THEN END 110 READ START 120 FOR ADDR=START TO START+CNT-1 130 READ BYTE:POKE ADDR,BYTE 135 NEXT ADDR 140 GOTO 100 150 DATA 3,5481,32,1,21 160 DATA 29,5377,141,217,22,169,16 170 DATA 141,23,22,169,23,141,24,22 180 DATA 169,49,141,30,22,169,64,141 190 DATA 12,0,169,21,141,13,0,96 200 DATA 1,7425,112,0 BUG: INIT does not work if you use drive numbers 4 through 8. FIX: Run the following program: 10 OPEN #1,12,0,"D:INIT.COM" 20 FOR I=1 TO 116 : GET #1,C : NEXT I 30 PUT #1,ASC("9") : CLOSE #1 Legacy Plans for DOS XL 4 were scrapped due to low demand and competition. OSS reissued OS/A+ 4.1, mainly for double-sided support. DOS XL, along with other OSS products, became part of ICD's catalog of Atari products in January 1988. However, DOS XL was dropped in favor of ICD's SpartaDOS. References Inside Atari DOS Introduction by Bill Wilkinson, 1982 A User's Guide and Reference Manual for DOS XL 2.30, 1983 OSS Newsletter - Spring 1984 OSS Newsletter - October 1984 External links Antic Vol.4 No.3 Everything You Wanted To Know About Every DOS Optimized Systems Software Atari 8-bit family software Atari operating systems Disk operating systems

Operating System (OS)

System software System software is software designed to provide a platform for other software. Examples of system software include operating systems (OS) like macOS, GNU/Linux, Android and Microsoft Windows, computational science software, game engines, search engines, industrial automation, and software as a service applications. Application software is software that allows users to do user-oriented tasks such as create text documents, play or develop games, create presentations, listen to music, draw pictures or browse the web. In the late 1940s, the early days of computing, most application software was custom-written by computer users to fit their specific hardware and requirements. System software was usually supplied by the manufacturer of the computer hardware and was intended to be used by most or all users of that system. Many operating systems come pre-packaged with basic application software. Such software is not considered system software when it can be uninstalled without affecting the functioning of other software. Examples of such software are games and simple editing tools supplied with Microsoft Windows, or software development toolchains supplied with many Linux distributions. Some gray areas between system and application software are web browsers integrated deeply into the operating system such as Internet Explorer in some versions of Microsoft Windows, or Chrome OS and Firefox OS where the browser functions as the only user interface and the only way to run programs (and other web browsers can not be installed in their place). Cloud-based software is another example of systems software, providing services to a software client (usually a web browser or a JavaScript application running in the web browser), not to the user directly. It is developed using system programming methodologies and systems programming languages. Operating systems or system control program The operating system (prominent examples being Microsoft Windows, macOS, Linux, and z/OS), allows the parts of a computer to work together by performing tasks like transferring data between memory and disks or rendering output onto a display device. It provides a platform (hardware abstraction layer) to run high-level system software and application software. A kernel is the core part of the operating system that defines an API for applications programs (including some system software) and an interface to device drivers. Device drivers, including also computer BIOS and device firmware, provide basic functionality to operate and control the hardware connected to or built into the computer. A user interface "allows users to interact with a computer." Either a command-line interface (CLI) or, since the 1980s a graphical user interface (GUI). This is the part of the operating system the user directly interacts with, it is considered an application and not system software. Utility software or system support programs Some organizations use the term systems programmer to describe a job function which is more accurately termed systems administrator. Software tools these employees use are then called system software. This utility software helps to analyze, configure, optimize and maintain the computer, such as virus protection. The term system software can also include software development tools (like a compiler, linker or debugger). See also System programming System programming language IBM mainframe utility programs System software of video game consoles From Microsoft: Xbox 360 system software Xbox One system software From Nintendo: Wii system software Wii U system software Nintendo DSi system software Nintendo 3DS system software Nintendo Switch system software From Sony: PlayStation 3 system software PlayStation 4 system software PlayStation Portable system software PlayStation Vita system software References External links

Operating System (OS)

Friend (operating system) The Friend OS or the Friend Unifying Platform is a network based Meta Operating System – a technology that can be used implementing a graphical user interface delivered through a browser, with a back-end that behaves like an operating system. This operating system connects resources and end-user software together in a seamless user experience that can be accessed anywhere. Additionally, it can be customized and prepped for any security requirements and is the first open source cloud operating system that aims to unify web applications and deliver an ecosystem for them to be used across all devices. Friend OS offers users a device agnostic computing environment accessible via the Friend Workspace, an HTML5 and JavaScript based user interface where file management and applications can be run. The project was started in 2014 by Friend Software Labs and they delivered their first open source version on GitHub in June 2017. They announced a partnership with the Golem project in November 2017. Friend will integrate their operating system environment into Golem’s distributed computing platform. Overview Friend OS is a multi-user meta operating system. Based on the Friend Core kernel, it is designed to be a complete operating system which will evolve and adapt with information and communication technologies. It employs a Blockchain based database structure for security, and is developed with decentralised flows of information in mind. Friend OS is designed to fit the Liquid Computing workflow concept by using a desktop environment and applications that can be accessed via a web browser without the need for any additional plugins, meaning it can run on any device, from a smartphone, to a high end workstation. It also fits the Web 4.0 outline of being a middleware where the Internet functions like an operating system. Where Friend OS enables more intuitive forms of resource management, or can be used between devices more easily. The term Web 4.0 itself is used to indicate another phase of the internet and World Wide Web — where humans and machines have a more symbiotic relationship. Friend OS fits within its framework, as well as future iterations of the Web, because it supports efficient and intelligent information flows. Components Friend Core Friend Core is Friend’s kernel. It behaves like a web server and operates as an operating system kernel for Friend applications. It also handles user sessions and resources that are available on the remote server. Friend Core is primarily written in C for speed, which allows it to handle requests on high bandwidth networks with 2ms response times. Features Friend Core is a small and fast web server with an OS inside of it. Written mainly in C, it provides low-level system calls to its native applications. Friend Core also integrates with various file systems, provides clustering with other core instances via Friend Network and ensures secure user data storage. Friend Workspace The Friend Workspace is the desktop and mobile environment of the Friend OS. It adapts to your device – whether it is a desktop computer, a tablet or a smart phone. It is highly collaborative – with a built-in chat, and an audio and video conferencing solution that’s just a click away. The Friend Workspace allows you to share files and collaboratively edit office documents. And if you’re away from the office – it will kindly send you push notifications when you have an important message Libraries Some of Friend Core's functionality is implemented as runtime linked libraries. This allows for the exchanging of pluggable libraries while Friend Core is running. This provides advantages when sand-boxing and handling decentralised data flows. Modules (Node.js/PHP/Python) Friend Core is modular. The modules extend the system with any functionality required by applications on the server side. The modules can be written using many programming languages like Node/JavaScript, PHP, Python, Perl or Java. The modules are user and group permission sensitive, allowing for various degrees of access control. Using a highly optimised core, time to first byte (TTFB) round trips are kept to a minimum. File System Drivers Friend Core provides a file system driver API that allows developers to build support for any file system or standards-based web resource using several programming languages. A DOS driver implements basic functions for reading and writing to various remote and cloud service disks such as Dropbox, Google Drive, SAMBA, and others. Friend Network Friend Core servers form a network between them for increased scalability, access to computing power, additional services and resources. Friend Network can also provide an open client-side/server-side decentralised and distributed supercomputing network which allows users to share resources and form workgroups. This one is owned, run and governed by token holders, and can act as auxiliary infrastructure for businesses and organisations. Frnd Token A global network needs an immutable bookkeeping system. The FRND Token uses Blockchain technology to trace all transactions in the Friend Network. And it adds a logic layer that can be utilised to form contractual relationships between users and vendors. It allows for decentralisation of the Friend Sky Computing network. Friend runs a variety of applications both natively and via remote sessions. Applications Web Suite Friend provides you with a Workspace and full office suite and connectivity to MS-office, GSuite and other comparable cloud services. It gives you complete freedom to choose where your data is processed and where it is stored. Easily drag and drop between all applications – it’s never been simpler to multitask online. Our Document, Presentation and Spreadsheet apps run on any device while letting you choose where you want to store your documents. Friend comes with a flexible suite of file systems that lets you store data both on-premise and using your preferred storage provider. Easy user and storage administration make your everyday life easier while keeping your documents safely under your control. Web Applications Friend OS is compatible with web applications. As the OS is built using web technologies, applications hosted on the web can easily be executed inside the Friend Workspace. Friend Applications The Friend Workspace has its own set of APIs and protocols. Native Friend applications are fully integrated into the operating system and allow features such as pull down menus, managed windows and a range of GUI controls. They are localized therefore they operate much quicker than web hosted or Windows apps. Friend comes bundled with several applications including a native video, audio and text conferencing suite called Friend Chat. Windows Applications By routing through the Liberator application stack, a user can run Windows applications directly in the Friend Workspace, alongside Web and Friend applications. By integrating through the RDP protocol, the Windows applications act like they are native web applications. Users can perform functions such as transferring files from Friend disk drives directly into their your Windows applications as well as and copy and paste text from within the Friend Workspace. Friend Hydrogen Release history V.1.0.0 - First public open source release. V.1.1.0 - Second public open source release. V.1.2.0 - Third public open source release. V.1.2.4 - Release of Friend Hydrogen References External links TWiT FLOSS Weekly Friend special Open-source cloud applications Operating systems

Operating System (OS)

Linux distribution A Linux distribution (often abbreviated as distro) is an operating system made from a software collection that includes the Linux kernel and, often, a package management system. Linux users usually obtain their operating system by downloading one of the Linux distributions, which are available for a wide variety of systems ranging from embedded devices (for example, OpenWrt) and personal computers (for example, Linux Mint) to powerful supercomputers (for example, Rocks Cluster Distribution). A typical Linux distribution comprises a Linux kernel, GNU tools and libraries, additional software, documentation, a window system (the most common being the X Window System, or, more recently, Wayland), a window manager, and a desktop environment. Most of the included software is free and open-source software made available both as compiled binaries and in source code form, allowing modifications to the original software. Usually, Linux distributions optionally include some proprietary software that may not be available in source code form, such as binary blobs required for some device drivers. A Linux distribution may also be described as a particular assortment of application and utility software (various GNU tools and libraries, for example), packaged together with the Linux kernel in such a way that its capabilities meet the needs of many users. The software is usually adapted to the distribution and then packaged into software packages by the distribution's maintainers. The software packages are available online in repositories, which are storage locations usually distributed around the world. Beside glue components, such as the distribution installers (for example, Debian-Installer and Anaconda) or the package management systems, there are only very few packages that are originally written from the ground up by the maintainers of a Linux distribution. Almost one thousand Linux distributions exist. Because of the huge availability of software, distributions have taken a wide variety of forms, including those suitable for use on desktops, servers, laptops, netbooks, mobile phones and tablets, as well as minimal environments typically for use in embedded systems. There are commercially backed distributions, such as Fedora Linux (Red Hat), openSUSE (SUSE) and Ubuntu (Canonical Ltd.), and entirely community-driven distributions, such as Debian, Slackware, Gentoo and Arch Linux. Most distributions come ready to use and pre-compiled for a specific instruction set, while some distributions (such as Gentoo) are distributed mostly in source code form and compiled locally during installation. History Linus Torvalds developed the Linux kernel and distributed its first version, 0.01, in 1991. Linux was initially distributed as source code only, and later as a pair of downloadable floppy disk images one bootable and containing the Linux kernel itself, and the other with a set of GNU utilities and tools for setting up a file system. Since the installation procedure was complicated, especially in the face of growing amounts of available software, distributions sprang up to simplify this. Early distributions included the following: H. J. Lu's "Boot-root", the aforementioned disk image pair with the kernel and the absolute minimal tools to get started, in late 1991 MCC Interim Linux, which was made available to the public for download in February 1992 Softlanding Linux System (SLS), released in 1992, was the most comprehensive distribution for a short time, including the X Window System Yggdrasil Linux/GNU/X, a commercial distribution first released in December 1992 The two oldest and still active distribution projects started in 1993. The SLS distribution was not well maintained, so in July 1993 a new distribution, called Slackware and based on SLS, was released by Patrick Volkerding. Also dissatisfied with SLS, Ian Murdock set to create a free distribution by founding Debian, which had its first release in December 1993. Users were attracted to Linux distributions as alternatives to the DOS and Microsoft Windows operating systems on IBM PC compatible computers, Mac OS on the Apple Macintosh, and proprietary versions of Unix. Most early adopters were familiar with Unix from work or school. They embraced Linux distributions for their low (if any) cost, and availability of the source code for most or all of the software included. As of 2017, Linux has become more popular in server and embedded devices markets than in the desktop market. For example, Linux is used on over 50% of web servers, whereas its desktop market share is about 3.7%. Components Many Linux distributions provide an installation system akin to that provided with other modern operating systems. On the other hand, some distributions, including Gentoo Linux, provide only the binaries of a basic kernel, compilation tools, and an installer; the installer compiles all the requested software for the specific architecture of the user's computer, using these tools and the provided source code. Package management Distributions are normally segmented into packages. Each package contains a specific application or service. Examples of packages are a library for handling the PNG image format, a collection of fonts or a web browser. The package is typically provided as compiled code, with installation and removal of packages handled by a package management system (PMS) rather than a simple file archiver. Each package intended for such a PMS contains meta-information such as a package description, version, and "dependencies". The package management system can evaluate this meta-information to allow package searches, to perform an automatic upgrade to a newer version, to check that all dependencies of a package are fulfilled, and/or to fulfill them automatically. Although Linux distributions typically contain much more software than proprietary operating systems, it is normal for local administrators to also install software not included in the distribution. An example would be a newer version of a software application than that supplied with a distribution, or an alternative to that chosen by the distribution (for example, KDE Plasma Workspaces rather than GNOME or vice versa for the user interface layer). If the additional software is distributed in source-only form, this approach requires local compilation. However, if additional software is locally added, the "state" of the local system may fall out of synchronization with the state of the package manager's database. If so, the local administrator will be required to take additional measures to ensure the entire system is kept up to date. The package manager may no longer be able to do so automatically. Most distributions install packages, including the kernel and other core operating system components, in a predetermined configuration. Few now require or even permit configuration adjustments at first install time. This makes installation less daunting, particularly for new users, but is not always acceptable. For specific requirements, much software must be carefully configured to be useful, to work correctly with other software, or to be secure, and local administrators are often obliged to spend time reviewing and reconfiguring assorted software. Some distributions go to considerable lengths to specifically adjust and customize most or all of the software included in the distribution. Not all do so. Some distributions provide configuration tools to assist in this process. By replacing everything provided in a distribution, an administrator may reach a "distribution-less" state: everything was retrieved, compiled, configured, and installed locally. It is possible to build such a system from scratch, avoiding a distribution altogether. One needs a way to generate the first binaries until the system is self-hosting. This can be done via compilation on another system capable of building binaries for the intended target (possibly by cross-compilation). For example, see Linux From Scratch. Types and trends In broad terms, Linux distributions may be: Commercial or non-commercial Designed for enterprise users, power users, or for home users Supported on multiple types of hardware, or platform-specific, even to the extent of certification by the platform vendor Designed for servers, desktops, or embedded devices General purpose or highly specialized toward specific machine functionalities (e.g. firewalls, network routers, and computer clusters) Targeted at specific user groups, for example through language internationalization and localization, or through inclusion of many music production or scientific computing packages Built primarily for security, usability, portability, or comprehensiveness Standard release or rolling release, see below. The diversity of Linux distributions is due to technical, organizational, and philosophical variation among vendors and users. The permissive licensing of free software means that users with sufficient knowledge and interest can customize any existing distribution, or design one to suit their own needs. Rolling distributions Rolling Linux distributions are kept updated using small and frequent updates. The terms partially rolling and partly rolling (along with synonyms semi-rolling and half-rolling), fully rolling, truly rolling and optionally rolling are sometimes used by software developers and users. Repositories of rolling distributions usually contain very recent software releases – often the latest stable software releases available. They have pseudo-releases and installation media that are simply a snapshot of the software distribution at the time of the release of the installation image. Typically, a rolling release operating system installed from an older installation medium can be fully updated post-installation to a current state. Depending on the use case, there can be pros and cons to both standard release and rolling release software development methodologies. In terms of the software development process, standard releases require significant development effort being spent on keeping old versions up to date due to propagating bug fixes back to the newest branch, versus focusing more on the newest development branch. Also, unlike rolling releases, standard releases require more than one code branch to be developed and maintained, which increases the software development and software maintenance workload of the software developers and software maintainers. On the other hand, software features and technology planning are easier in standard releases due to a better understanding of upcoming features in the next version(s). Software release cycles can also be synchronized with those of major upstream software projects, such as desktop environments. As far as the user experience, standard releases are often viewed as more stable and bug-free since software conflicts can be more easily addressed and the software stack more thoroughly tested and evaluated, during the software development cycle. For this reason, they tend to be the preferred choice in enterprise environments and mission-critical tasks. However, rolling releases offer more current software which can also provide increased stability and fewer software bugs along with the additional benefits of new features, greater functionality, faster running speeds, and improved system and application security. Regarding software security, the rolling release model can have advantages in timely security updates, fixing system or application security bugs and vulnerabilities, that standard releases may have to wait till the next release for or patch in various versions. In a rolling release distribution, where the user has chosen to run it as a highly dynamic system, the constant flux of software packages can introduce new unintended vulnerabilities. Installation-free distributions (live CD/USB) A "live" distribution is a Linux distribution that can be booted from removable storage media such as optical discs or USB flash drives, instead of being installed on and booted from a hard disk drive. The portability of installation-free distributions makes them advantageous for applications such as demonstrations, borrowing someone else's computer, rescue operations, or as installation media for a standard distribution. When the operating system is booted from a read-only medium such as a CD or DVD, any user data that needs to be retained between sessions cannot be stored on the boot device but must be written to another storage device, such as a USB flash drive or a hard disk drive. Many Linux distributions provide a "live" form in addition to their conventional form, which is a network-based or removable-media image intended to be used only for installation; such distributions include SUSE, Ubuntu, Linux Mint, MEPIS and Fedora Linux. Some distributions, including Knoppix, Puppy Linux, Devil-Linux, SuperGamer, SliTaz GNU/Linux and dyne:bolic, are designed primarily for live use. Additionally, some minimal distributions can be run directly from as little space as one floppy disk without the need to change the contents of the system's hard disk drive. Examples The website DistroWatch lists many Linux distributions, and displays some of the ones that have the most web traffic on the site. The Wikimedia Foundation released an analysis of the browser User Agents of visitors to WMF websites until 2015, which includes details of the most popular Operating System identifiers, including some Linux distributions. Many of the popular distributions are listed below. Widely used GNU-based or GNU-compatible distributions Debian, a non-commercial distribution and one of the earliest, maintained by a volunteer developer community with a strong commitment to free software principles and democratic project management. Knoppix, the first Live CD distribution to run completely from removable media without installation to a hard disk, derived from Debian. Linux Mint Debian Edition (LMDE) uses Debian packages directly (rather than Ubuntu's) Ubuntu, a desktop and server distribution derived from Debian, maintained by British company Canonical Ltd. There are several distributions based on Ubuntu that mainly replace the GNOME stock desktop environment, like: Kubuntu based on KDE, Lubuntu based on LXQT, Xubuntu based on XFCE, Ubuntu MATE based on MATE, Ubuntu Budgie based on Budgie. Other official forks have specific uses like: Ubuntu Kylin for Chinese-speaking users, or Ubuntu Studio for media content creators. Linux Mint, a distribution based on and compatible with Ubuntu. Supports multiple desktop environments, among others GNOME Shell fork Cinnamon and GNOME 2 fork MATE. Fedora Linux, a community distribution sponsored by American company Red Hat and the successor to the company's previous offering, Red Hat Linux. It aims to be a technology testbed for Red Hat's commercial Linux offering, where new open-source software is prototyped, developed, and tested in a communal setting before maturing into Red Hat Enterprise Linux. Red Hat Enterprise Linux (RHEL), a derivative of Fedora Linux, maintained and commercially supported by Red Hat. It seeks to provide tested, secure, and stable Linux server and workstation support to businesses. CentOS, a distribution derived from the same sources used by Red Hat, maintained by a dedicated volunteer community of developers with both 100% Red Hat-compatible versions and an upgraded version that is not always 100% upstream compatible. Oracle Linux, which is a derivative of Red Hat Enterprise Linux, maintained and commercially supported by Oracle Mandriva Linux was a Red Hat Linux derivative popular in several European countries and Brazil, backed by the French company of the same name. After the company went bankrupt, it was superseded by OpenMandriva Lx, although a number of derivatives now have a larger user base. Mageia, a community fork of Mandriva Linux created in 2010 PCLinuxOS, a derivative of Mandriva, which grew from a group of packages into a community-spawned desktop distribution openSUSE, a community distribution mainly sponsored by German company SUSE. SUSE Linux Enterprise, derived from openSUSE, maintained and commercially supported by SUSE Arch Linux, a rolling release distribution targeted at experienced Linux users and maintained by a volunteer community, offers official binary packages and a wide range of unofficial user-submitted source packages. Packages are usually defined by a single PKGBUILD text file. Manjaro Linux, a derivative of Arch Linux that includes a graphical installer and other ease-of-use features for less experienced Linux users. Gentoo, a distribution targeted at power users, known for its FreeBSD Ports-like automated system for compiling applications from source code Slackware, created in 1993, one of the first Linux distributions and among the earliest still maintained, committed to remain highly Unix-like and easily modifiable by end users Linux kernel based operating systems Android, Google's commercial operating system based on Android OSP that runs on many devices such as smart phones, smart TVs, set-top boxes. Chrome OS, Google's commercial operating system based on Chromium OS that only runs on Chromebooks, Chromeboxes and tablet computers. Like Android, it has the Google Play Store and other Google apps. Support for applications that require GNU compatibility is available through a virtual machine called Crostini and referred to by Google as Linux support, see Chromebook#Integration with Linux. Whether the above operating systems count as a "Linux distribution" is a controversial topic. They use the Linux kernel, so the Linux Foundation and Chris DiBona, Google's open-source chief, agree that Android is a Linux distribution; others, such as Google engineer Patrick Brady, disagree by noting the lack of support for many GNU tools in Android, including glibc. Other Linux kernel based operating systems include Cyanogenmod, its fork LineageOS, Android-x86 and recently Tizen, Mer/Sailfish OS and KaiOS. Lightweight distributions Lightweight Linux distributions are those that have been designed with support for older hardware in mind, allowing older hardware to still be used productively, or, for maximum possible speed in newer hardware by leaving more resources available for use by applications. Examples include Tiny Core Linux, Puppy Linux and Slitaz. Niche distributions Other distributions target specific niches, such as: Routers for example, targeted by the tiny embedded router distribution OpenWrt Internet of things for example, targeted by Ubuntu Core Home theater PCs for example, targeted by KnoppMyth, Kodi (former XBMC) and Mythbuntu Specific platforms for example, Raspberry Pi OS targets the Raspberry Pi platform Education examples are Edubuntu and Karoshi, server systems based on PCLinuxOS Scientific computer servers and workstations for example, targeted by Scientific Linux Digital audio workstations for music production for example, targeted by Ubuntu Studio Computer Security, digital forensics and penetration testing examples are Kali Linux and Parrot Security OS Privacy and anonymity for example, targeted by Tails, Whonix, Qubes, or FreedomBox Offline use for example, Endless OS Microsoft's Azure Sphere Interdistribution issues The Free Standards Group is an organization formed by major software and hardware vendors that aims to improve interoperability between different distributions. Among their proposed standards are the Linux Standard Base, which defines a common ABI and packaging system for Linux, and the Filesystem Hierarchy Standard which recommends a standard filenaming chart, notably the basic directory names found on the root of the tree of any Linux filesystem. Those standards, however, see limited use, even among the distributions developed by members of the organization. The diversity of Linux distributions means that not all software runs on all distributions, depending on what libraries and other system attributes are required. Packaged software and software repositories are usually specific to a particular distribution, though cross-installation is sometimes possible on closely related distributions. Tools for choosing a distribution The process of constantly switching between distributions is often referred to as "distro hopping". Virtual machines such as VirtualBox and VMware Workstation virtualize hardware allowing users to test live media on a virtual machine. Some websites like DistroWatch offer lists of distributions, and link to screenshots of operating systems as a way to get a first impression of various distributions. There are tools available to help people select an appropriate distribution, such as several versions of the Linux Distribution Chooser, and the universal package search tool whohas. There are easy ways to try out several Linux distributions before deciding on one: Multi Distro is a Live CD that contains nine space-saving distributions. Installation There are several ways to install a Linux distribution. The most common method of installing Linux is by booting from a live USB memory stick, which can be created by using a USB image writer application and the ISO image, which can be downloaded from the various Linux distribution websites. DVD disks, CD disks, network installations and even other hard drives can also be used as "installation media". In the 1990s Linux distributions were installed using sets of floppies but this has been abandoned by all major distributions. By the 2000s many distributions offered CD and DVD sets with the vital packages on the first disc and less important packages on later ones. Some distributions, such as Debian also enabled installation over a network after booting from either a set of floppies or a CD with only a small amount of data on it. New users tend to begin by partitioning a hard drive in order to keep their previously installed operating system. The Linux distribution can then be installed on its own separate partition without affecting previously saved data. In a Live CD setup, the computer boots the entire operating system from CD without first installing it on the computer's hard disk. Many distributions have a Live CD installer, where the computer boots the operating system from the disk, and it can then be installed on the computer's hard disk, providing a seamless transition from the OS running from the CD to the OS running from the hard disk. Both servers and personal computers that come with Linux already installed are available from vendors including Hewlett-Packard, Dell and System76. On embedded devices, Linux is typically held in the device's firmware and may or may not be consumer-accessible. Anaconda, one of the more popular installers, is used by Red Hat Enterprise Linux, Fedora (which uses the Fedora Media Writer) and other distributions to simplify the installation process. Debian, Ubuntu and many others use Debian-Installer. Installation via an existing operating system Some distributions let the user install Linux on top of their current system, such as WinLinux or coLinux. Linux is installed to the Windows hard disk partition, and can be started from inside Windows itself. Virtual machines (such as VirtualBox or VMware) also make it possible for Linux to be run inside another OS. The VM software simulates a separate computer onto which the Linux system is installed. After installation, the virtual machine can be booted as if it were an independent computer. Various tools are also available to perform full dual-boot installations from existing platforms without a CD, most notably: The (now deprecated) Wubi installer, which allows Windows users to download and install Ubuntu or its derivatives into a FAT32 or an NTFS partition without an installation CD, allowing users to easily dual boot between either operating system on the same hard drive without losing data. Replaced by Ubiquity. Win32-loader, which is in the process of being integrated in official Debian CDs/DVDs, and allows Windows users to install Debian without a CD, though it performs a network installation and thereby requires repartitioning UNetbootin, which allows Windows and Linux users to perform similar no-CD network installations for a wide variety of Linux distributions and additionally provides live USB creation support Proprietary software Some specific proprietary software products are not available in any form for Linux. As of September 2015, the Steam gaming service has 1,500 games available on Linux, compared to 2,323 games for Mac and 6,500 Windows games. Emulation and API-translation projects like Wine and CrossOver make it possible to run non-Linux-based software on Linux systems, either by emulating a proprietary operating system or by translating proprietary API calls (e.g., calls to Microsoft's Win32 or DirectX APIs) into native Linux API calls. A virtual machine can also be used to run a proprietary OS (like Microsoft Windows) on top of Linux. OEM contracts Computer hardware is usually sold with an operating system other than Linux already installed by the original equipment manufacturer (OEM). In the case of IBM PC compatibles the OS is usually Microsoft Windows; in the case of Apple Macintosh computers it has always been a version of Apple's OS, currently macOS; Sun Microsystems sold SPARC hardware with the Solaris installed; video game consoles such as the Xbox, PlayStation, and Wii each have their own proprietary OS. This limits Linux's market share: consumers are unaware that an alternative exists, they must make a conscious effort to use a different operating system, and they must either perform the actual installation themselves, or depend on support from a friend, relative, or computer professional. However, it is possible to buy hardware with Linux already installed. Lenovo, Hewlett-Packard, Dell, Affordy, Purism, Pine64 and System76 all sell general-purpose Linux laptops. Custom-order PC manufacturers will also build Linux systems, but possibly with the Windows key on the keyboard. Fixstars Solutions (formerly Terra Soft) sells Macintosh computers and PlayStation 3 consoles with Yellow Dog Linux installed. It is more common to find embedded devices sold with Linux as the default manufacturer-supported OS, including the Linksys NSLU2 NAS device, TiVo's line of personal video recorders, and Linux-based cellphones (including Android smartphones), PDAs, and portable music players. The current Microsoft Windows license lets the manufacturer determine the refund policy. With previous versions of Windows, it was possible to obtain a refund if the manufacturer failed to provide the refund by litigation in the small claims courts. On February 15, 1999, a group of Linux users in Orange County, California held a "Windows Refund Day" protest in an attempt to pressure Microsoft into issuing them refunds. In France, the Linuxfrench and AFUL (French speaking Libre Software Users' Association) organizations along with free software activist Roberto Di Cosmo started a "Windows Detax" movement, which led to a 2006 petition against "racketiciels" (translation: Racketware) with 39,415 signatories and the DGCCRF branch of the French government filing several complaints against bundled software. On March 24, 2014, a new international petition was launched by AFUL on the Avaaz platform, translated into several languages and supported by many organizations around the world. Statistics There are no official figures on popularity, adoption, downloads or installed base of Linux distributions. There are also no official figures for the total number of Linux systems, partly due to the difficulty of quantifying the number of PCs running Linux (see Desktop Linux adoption), since many users download Linux distributions. Hence, the sales figures for Linux systems and commercial Linux distributions indicate a much lower number of Linux systems and level of Linux adoption than is the case; this is mainly due to Linux being free and open-source software that can be downloaded free of charge. A Linux Counter Project had kept track of a running guesstimate of the number of Linux systems, but did not distinguish between rolling release and standard release distributions. It ceased operation in August 2018, though a few related blog posts were created through October 2018. Desktop usage statistical reports for particular Linux distributions have been collected and published since July 2014 by the Linux Hardware Project. See also Comparison of Linux distributions Light-weight Linux distribution List of Linux distributions References External links The LWN.net Linux Distribution List – a categorized list with information about each entry List of GNU/Linux distributions considered free by the Free Software Foundation Google's approach to a large-scale live upgrading between two widely different Linux distributions: presentation and text version, LinuxCon 2013, by Marc Merlin Rolling release vs. fixed release Linux, ZDNet, February 3, 2015, by Steven J. Vaughan-Nichols DistroTest - test any Linux Distro without installing Linus Torvalds

Operating System (OS)

Apple DOS Apple DOS is the family of disk operating systems for the Apple II series of microcomputers from late 1978 through early 1983. It was superseded by ProDOS in 1983. Apple DOS has three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only in the case of Apple DOS 3.2 did that minor release receive its own version number, Apple DOS 3.2.1. The best-known and most-used version is Apple DOS 3.3 in the 1980 and 1983 releases. Prior to the release of Apple DOS 3.1, Apple users had to rely on audio cassette tapes for data storage and retrieval. Version history When Apple Computer introduced the Apple II in April 1977, the new computer had no disk drive or disk operating system (DOS). Although Apple co-founder Steve Wozniak designed the Disk II controller late that year, and believed that he could have written a DOS, his co-founder Steve Jobs decided to outsource the task. The company considered using Digital Research's CP/M, but Wozniak sought an operating system that was easier to use. On 10 April 1978 Apple signed a $13,000 contract with Shepardson Microsystems to write a DOS and deliver it within 35 days. Apple provided detailed specifications, and early Apple employee Randy Wigginton worked closely with Shepardson's Paul Laughton as the latter wrote the operating system with punched cards and a minicomputer. There was no Apple DOS 1 or 2. Versions 0.1 through 2.8 were serially enumerated revisions during development, which might as well have been called builds 1 through 28. Apple DOS 3.0, a renamed issue of version 2.8, was never publicly released due to bugs. Apple published no official documentation until release 3.2. Apple DOS 3.1 was publicly released in June 1978, slightly more than one year after the Apple II was introduced, becoming the first disk-based operating system for any Apple computer. A bug-fix release came later, addressing a problem by means of its utility, which was used to create Apple DOS master (bootable) disks: The built-in command created disks that could be booted only on machines with at least the same amount of memory as the one that had created them. includes a self-relocating version of DOS that boots on Apples with any memory configuration. Apple DOS 3.2 was released in 1979 to reflect changes in computer booting methods that were built into the successor of the Apple II, the Apple II Plus. New firmware included an auto-start feature which automatically found a disk controller and booted from it when the system was powered up—earning it the name "Autostart ROM". DOS 3.2.1 was then released in July of 1979 with some minor bug fixes. Apple DOS 3.3 was released in 1980. It improves various functions of release 3.2, while also allowing for large gains in available floppy disk storage; the newer P5A/P6A PROMs in the disk controller enabled the reading and writing of data at a higher density, so instead of 13 sectors (3.25 KiB), 16 sectors (4 KiB) of data can be stored per disk track, increasing the capacity from 113.75 KB to 140 KB per disk side 16 KB of which is used by filesystem overhead and a copy of DOS, on a DOS 3.3-formatted disk, leaving 124 KB for user programs and data. DOS 3.3 is, however, not backward compatible; it cannot read or write DOS 3.2 disks. To address this problem, Apple Computer released a utility called "MUFFIN" to migrate Apple DOS 3.2 files and programs to version 3.3 disks. Apple never offered a utility to copy in the other direction. To migrate Apple DOS 3.3 files back to version 3.2 disks, someone wrote a "NIFFUM" utility. There are also commercial utilities (such as Copy II Plus) that can copy files from and to either format (and eventually ProDOS as well). Release 3.3 also improves the ability to switch between Integer BASIC and Applesoft BASIC, if the computer has a language card (RAM expansion) or firmware card. Technical details Apple DOS 3.1 disks use 13 sectors of data per track, each sector being 256 B. It uses 35 tracks per disk side, and can access only one side of the floppy disk, unless the user flipped the disk over. This gives the user a total storage capacity of 113.75 KB per side, of which about 10 KB are used to store DOS itself and the disk directory, leaving about 100 KB for user programs. The first layer of the operating system is called RWTS, which stands for "read/write track sector". This layer consists of subroutines for track seeking, sector reading and writing, and disk formatting. An API called the File Manager was built on top of this, and implements functions to open, close, read, write, delete, lock (i.e. write-protect), unlock (i.e. write-enable), and rename files, and to verify a file's structural integrity. There is also a catalog function, for listing files on the diskette, and an "init" function, which formats a disk for use with DOS, storing a copy of DOS on the first three tracks, and storing a startup program (usually called HELLO) that is auto-started when this disk is booted from. On top of the File Manager API, the main DOS routines are implemented which hook into the machine's BASIC interpreter and intercept all disk commands. It provides BLOAD, BSAVE, and BRUN for storing, loading, and running binary executables. LOAD, RUN, and SAVE are provided for BASIC programs, and an EXEC was provided for running text-based batch files consisting of BASIC and DOS commands. Finally, four types of files exist, identified by letters in a catalog listing: I – Integer BASIC programs (stored in a compact format, not plain-text) A – Applesoft BASIC programs (also stored in a packed, space-saving format) B – Binary files, either executable machine-language programs, or data files T – ASCII text files (or plain-text, unpacked batch files) There are four additional file types; "R", "S", and an additional "A" and "B", none of which are fully supported. DOS recognizes these types for catalog listings only, and there are no direct ways to manipulate these types of files. The "R" type found some use for relocatable binary executable files. A few programs support the "S" type as data files. A call vector table in the region of $03D0–03FF allows programs to find DOS wherever it is loaded in the system memory. For example, if the DOS hooked into the BASIC CLI stops functioning, it can be reinitialized by calling location $03D0 (976) hence the traditional "3D0G" ("3D0 go") command to return to BASIC from the System Monitor. Boot loader The process of loading Apple DOS involves a series of very tiny programs, each of which carries the loading process forward a few steps before passing control to the next program in the chain. Originally, the Apple II ROM did not support disk booting at all. At power-up it would display the System Monitor prompt. Both the Monitor and Integer BASIC have commands to redirect printing to a printer driver in a designated slot, so the conventional way to boot from disk then was to command the computer to start "printing" to the disk interface card, typically installed in slot 6, using the command 6 Control-P (from the ML monitor) or PR#6 (from BASIC). When the monitor or BASIC issued the next prompt character, the computer would call the ROM routines on the disk card to "print" to it, which would then proceed with the boot sequence. (One could use input redirection to similar ends.) Alternatively, from the ML monitor, the user could type the slot number, typing C600G to invoke the controller's boot code directly. When the Apple II Plus was introduced, it included the ability to scan each expansion slot (working downward from slot 7 to slot 1) for a bootable expansion card ROM, and automatically call it. The expansion card ROM boot code attempts to boot from drive 1 of the controller by moving the read/write arm to track zero and attempting to read 256 bytes from sector zero of that track. (If no readable disk is available, the drive spins indefinitely until one is provided and the drive door is closed.) Sector zero contains a small program which instructs the computer to read sectors 0 through 9 of track zero into memory using part of the ROM boot code (rereading sector 0 in the process). The program in sectors 1–9 of track 0, including the complete RWTS code, then proceeds to load tracks 1 and 2, which contain the rest of DOS. On a system master disk, code is also included to determine the computer's RAM configuration and relocate DOS as high into system memory as possible, up to the 48 KB limit of the Apple II's main memory ($BFFF). Once DOS is loaded into memory, it attempts to load and execute a startup program as indicated in the DOS program code. This is commonly a BASIC language program named HELLO (or some other name) but DOS can be modified to run other types of programs at startup, such as an executable binary file. The appearance of the right-hand bracket (]) on the screen is an indication to the user that an Applesoft BASIC startup program is loading, while a greater-than symbol (>) indicates that an Integer BASIC program is loading. (These are the prompts for the respective versions of BASIC, which are being initialized at this point.) The startup program then begins executing. Integer BASIC and Applesoft BASIC support The original Apple II included BASIC interpreter in ROM known originally as Apple BASIC and later as Integer BASIC. Variables in this language can only handle integer numbers ranging from −32,768 to +32,767 (16-bit binary values); floating point numbers are not supported. Apple commissioned Microsoft to develop Applesoft BASIC, capable of handling floating-point numbers. Applesoft BASIC cannot run Integer BASIC programs, causing some users to resist upgrading to it. DOS 3.3 was released when Applesoft BASIC was standard in ROM on the Apple II Plus, so Apple designed it to support switching back and forth between the two BASIC interpreters. Integer BASIC is loaded into RAM on the language card of Apple IIs (if present) and by typing FP or INT from BASIC, the user can switch between either version. Decline After 1980, Apple DOS entered into a state of stagnation as Apple concentrated its efforts on the ill-fated Apple III computer and its SOS operating system. Two more versions of Apple DOS, both still called DOS 3.3 but with some bug fixes and better support for the new Apple IIe model, were released in early and mid-1983. Without third-party patches, Apple DOS can only read floppy disks running in a 5.25-inch Disk II drive and cannot access any other media, such as hard disk drives, virtual RAM drives, or 3.5-inch floppy disk drives. The structure of Apple DOS disks (particularly the free sector map, which was restricted to part of a single sector) is such that it is not possible to have more than 400 KB available at a time per drive without a major rewrite of almost all sections of the code; this is the main reason Apple abandoned this iteration of DOS in 1983, when Apple DOS was entirely replaced by ProDOS. ProDOS retains the 16-sector low-level format of DOS 3.3 for 5.25 inch disks, but introduces a new high-level format that is suitable for devices of up to 32 MB; this makes it suitable for hard disks from that era and 3.5-inch floppies. All the Apple computers from the II Plus onward can run both DOS 3.3 and ProDOS, the Plus requiring a "Language Card" memory expansion to use ProDOS; the e and later models have built-in Language Card hardware, and so can run ProDOS straight. ProDOS includes software to copy files from Apple DOS disks. However, many people who had no need for the improvements of ProDOS (and who did not like its much higher memory footprint) continued using Apple DOS or one of its clones long after 1983. The Apple convention of storing a bootable OS on every single floppy disk means that commercial software can be used no matter what OS the user owns. A program called DOS.MASTER enables users to have multiple virtual DOS 3.3 partitions on a larger ProDOS volume, which allows the use of many floppy-based DOS programs with a hard disk. Shortly after ProDOS came out, Apple withdrew permission from third parties to redistribute DOS 3.3, but granted one company, Syndicomm, an exclusive license to resell DOS 3.3. Commercial games usually did not use Apple DOS, instead having their own custom disk routines for copy protection purposes as well as for performance. Performance improvements DOS's RWTS routine can read or write a track in two revolutions with proper interleaving. A sector of the spinning disk passes under the read/write head while the RWTS routine is decoding the just-read sector (or encoding the next one to be written), and if this missed sector is the next one needed, DOS needs to wait nearly an entire revolution of the disk for the sector to come around again. This is called "blowing a rev" and is a well-understood performance bottleneck in disk systems. To avoid this, the sectors on a DOS disk are arranged in an interleaved order: 0 7 e 6 d 5 c 4 b 3 a 2 9 1 8 f Later, ProDOS arranged the sectors in this order: 0 8 1 9 2 a 3 b 4 c 5 d 6 e 7 f When reading and decoding sector 0, then sector 8 passes by, so that sector 1, the next sector likely to be needed, will be available without waiting. When reading sector 7, two unneeded sectors, f and 0, pass by before sector 8 is available, and when reading sector 15, the drive will always have to wait an extra revolution for sector 0 on the same track. However, the sector 0 actually needed in most cases will be on the next-higher track, and that track can be arranged relative to the last one to allow the needed time to decode the just-read sector and move the head before sector 0 comes around. On average, a full track can be read in two revolutions of the disk. Unfortunately, the early DOS File Manager subverted this efficiency by copying bytes read from or written to a file one at a time between a disk buffer and main memory, requiring more time and resulting in DOS constantly blowing revs when reading or writing files. Programs became available early on to format disks with modified sector interleaves; these disks give DOS more time between sectors to copy the data, ameliorating the problem. Later, programmers outside Apple rewrote the File Manager routines to avoid making the extra copy for most sectors of a file; RWTS was instructed to read or write sectors directly to or from main memory rather than from a disk buffer whenever a full sector was to be transferred. An early "patch" to provide this functionality was published in Call-A.P.P.L.E.. Speedups in the LOAD command of three to five times were typical. This functionality soon appeared in commercial products, such as Pronto-DOS, Diversi-DOS, Hyper-DOS, and David-DOS, along with additional features, but it was never used in an official Apple DOS release. Similar functionality was, however, employed by Apple's successor operating system, ProDOS. The Apple IIGS-specific operating system GS/OS would eventually employ an even more efficient "scatter read" technique that would read any sector that happened to be passing under the read head if it was needed for the file being read. Source code release In 2013, more than 35 years after the Apple II debuted, the original Apple DOS source code was released by the Computer History Museum on its website. It was donated by the original author, Paul Laughton. References Further reading External links Paul Laughton's account of writing DOS 3.1 Apple II History: DOS A2Central.com - Apple II news and downloads Everything2.com's DOS 3.1 Article Apple II DOS version 3.1 source code (1978, released in 2013 with the permission of Apple Inc.) DOS DOS, Apple Discontinued operating systems Disk operating systems 1978 software

Operating System (OS)

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions of AmigaOS required the Motorola 68000 series of 16-bit and 32-bit microprocessors. Later versions were developed by Haage & Partner (AmigaOS 3.5 and 3.9) and then Hyperion Entertainment (AmigaOS 4.0-4.1). A PowerPC microprocessor is required for the most recent release, AmigaOS 4. AmigaOS is a single-user operating system based on a preemptive multitasking kernel, called Exec. It includes an abstraction of the Amiga's hardware, a disk operating system called AmigaDOS, a windowing system API called Intuition and a desktop file manager called Workbench. The Amiga intellectual property is fragmented between Amiga Inc., Cloanto, and Hyperion Entertainment. The copyrights for works created up to 1993 are owned by Cloanto. In 2001, Amiga Inc. contracted AmigaOS 4 development to Hyperion Entertainment and, in 2009 they granted Hyperion an exclusive, perpetual, worldwide license to AmigaOS 3.1 in order to develop and market AmigaOS 4 and subsequent versions. On December 29, 2015, the AmigaOS 3.1 source code leaked to the web; this was confirmed by the licensee, Hyperion Entertainment. Components AmigaOS is a single-user operating system based on a preemptive multitasking kernel, called Exec. AmigaOS provides an abstraction of the Amiga's hardware, a disk operating system called AmigaDOS, a windowing system API called Intuition and a desktop file manager called Workbench. A command-line interface (CLI), called AmigaShell, is also integrated into the system, though it also is entirely window-based. The CLI and Workbench components share the same privileges. Notably, AmigaOS lacks any built-in memory protection. AmigaOS is formed from two parts, namely, a firmware component called Kickstart and a software portion usually referred to as Workbench. Up until AmigaOS 3.1, matching versions of Kickstart and Workbench were typically released together. However, since AmigaOS 3.5, the first release after Commodore's demise, only the software component has been updated and the role of Kickstart has been diminished somewhat. Firmware updates may still be applied by patching at system boot. That was until 2018 when Hyperion Entertainment (license holder to AmigaOS 3.1) released AmigaOS 3.1.4 with an updated Kickstart ROM to go with it. Firmware and bootloader Kickstart is the bootstrap firmware, usually stored in ROM. Kickstart contains the code needed to boot standard Amiga hardware and many of the core components of AmigaOS. The function of Kickstart is comparable to the BIOS plus the main operating system kernel in IBM PC compatibles. However, Kickstart provides more functionality available at boot time than would typically be expected on PC, for example, the full windowing environment. Kickstart contains many core parts of the Amiga's operating system, such as Exec, Intuition, the core of AmigaDOS and functionality to initialize Autoconfig-compliant expansion hardware. Later versions of the Kickstart contained drivers for IDE and SCSI controllers, PC card ports and other built-in hardware. Upon start-up or reset the Kickstart performs a number of diagnostic and system checks and then initializes the Amiga chipset and some core OS components. It will then examine connected boot devices and attempt to boot from the one with the highest boot priority. If no boot device is present a screen will be displayed asking the user to insert a boot disk, typically a floppy disk. At start-up Kickstart attempts to boot from a bootable device (typically, a floppy disk or hard disk drive). In the case of a floppy, the system reads the first two sectors of the disk (the bootblock), and executes any boot instructions stored there. Normally this code passes control back to the OS (invoking AmigaDOS and the GUI) and using the disk as the system boot volume. Any such disk, regardless of the other contents of the disk, was referred to as a "Boot disk" or "bootable disk". A bootblock could be added to a blank disk by use of the install command. Some games and demos on floppy disk used custom bootblocks, which allowed them to take over the boot sequence and manage the Amiga's hardware without AmigaOS. The bootblock became an obvious target for virus writers. Some games or demos that used a custom bootblock would not work if infected with a bootblock virus, as the code of the virus replaced the original. The first such virus was the SCA virus. Anti-virus attempts included custom bootblocks. These amended bootblock advertised the presence of the virus checker while checking the system for tell-tale signs of memory-resident viruses and then passed control back to the system. Unfortunately these could not be used on disks that already relied on a custom bootblock, but did alert users to potential trouble. Several of them also replicated themselves across other disks, becoming little more than viruses in their own right. Kernel Exec is the multi-tasking kernel of AmigaOS. Exec provides functionality for multi-tasking, memory allocation, interrupt handling and handling of dynamic shared libraries. It acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritized round-robin scheduling. Exec also provides access to other libraries and high-level inter-process communication via message passing. Other comparable microkernels have had performance problems because of the need to copy messages between address spaces. Since the Amiga has only one address space, Exec message passing is quite efficient. AmigaDOS AmigaDOS provides the disk operating system portion of the AmigaOS. This includes file systems, file and directory manipulation, the command-line interface, file redirection, console windows, and so on. Its interfaces offer facilities such as command redirection, piping, scripting with structured programming primitives, and a system of global and local variables. In AmigaOS 1.x, the AmigaDOS portion was based on TRIPOS, which is written in BCPL. Interfacing with it from other languages proved a difficult and error-prone task, and the port of TRIPOS was not very efficient. From AmigaOS 2.x onwards, AmigaDOS was rewritten in C and Assembler, retaining 1.x BCPL program compatibility, and it incorporated parts of the third-party AmigaDOS Resource Project, which had already written replacements for many of the BCPL utilities and interfaces. ARP also provided one of the first standardized file requesters for the Amiga, and introduced the use of more friendly UNIX-style wildcard (globbing) functions in command-line parameters. Other innovations were an improvement in the range of date formats accepted by commands and the facility to make a command resident, so that it only needs to be loaded into memory once and remains in memory to reduce the cost of loading in subsequent uses. In AmigaOS 4.0, the DOS abandoned the BCPL legacy completely and, starting from AmigaOS 4.1, it has been rewritten with full 64-bit support. File extensions are often used in AmigaOS, but they are not mandatory and they are not handled specially by the DOS, being instead just a conventional part of the file names. Executable programs are recognized using a magic number. Graphical user interface The native Amiga windowing system is called Intuition, which handles input from the keyboard and mouse and rendering of screens, windows and widgets. Prior to AmigaOS 2.0, there was no standardized look and feel, application developers had to write their own non-standard widgets. Commodore added the GadTools library and BOOPSI in AmigaOS 2.0, both of which provided standardized widgets. Commodore also published the Amiga User Interface Style Guide, which explained how applications should be laid out for consistency. Stefan Stuntz created a popular third-party widget library, based on BOOPSI, called Magic User Interface, or MUI. MorphOS uses MUI as its official toolkit, while AROS uses a MUI clone called Zune. AmigaOS 3.5 added another widget set, ReAction, also based on BOOPSI. An unusual feature of AmigaOS is the use of multiple screens shown on the same display. Each screen may have a different video resolution or color depth. AmigaOS 2.0 added support for public screens, allowing applications to open windows on other applications' screens. Prior to AmigaOS 2.0, only the Workbench screen was shared. A widget in the top-right corner of every screen allows screens to be cycled through. Screens can be overlaid by dragging each up or down by their title bars. AmigaOS 4 introduced screens that are draggable in any direction. File manager Workbench is the native graphical file manager and desktop environment of AmigaOS. Though the term Workbench was originally used to refer to the entire operating system, with the release of AmigaOS 3.1 the operating system was renamed AmigaOS and subsequently Workbench refers to the desktop manager only. As the name suggests, the metaphor of a workbench is used, rather than that of a desktop; directories are depicted as drawers, executable files are tools, data files are projects and GUI widgets are gadgets. In many other aspects the interface resembles Mac OS, with the main desktop showing icons of inserted disks and hard drive partitions, and a single menu bar at the top of every screen. Unlike the Macintosh mouse available at the time, the standard Amiga mouse has two buttons – the right mouse button operates the pull-down menus, with a "release to select" mechanism. Features Graphics Until the release of version 3, AmigaOS only natively supported the native Amiga graphics chipset, via graphics.library, which provides an API for geometric primitives, raster graphic operations and handling of sprites. As this API could be bypassed, some developers chose to avoid OS functionality for rendering and directly program the underlying hardware for gains in efficiency. Third-party graphics cards were initially supported via proprietary unofficial solutions. A later solution where AmigaOS could directly support any graphics system, was termed retargetable graphics (RTG). With AmigaOS 3.5, some RTG systems were bundled with the OS, allowing the use of common hardware cards other than the native Amiga chipsets. The main RTG systems are CyberGraphX, Picasso 96 and EGS. Some vector graphic libraries, like Cairo and Anti-Grain Geometry, are also available. Modern systems can use cross-platform SDL (simple DirectMedia Layer) engine for games and other multimedia programs. The Amiga did not have any inbuilt 3D graphics capability, and so had no standard 3D graphics API. Later, graphics card manufacturers and third-party developers provided their own standards, which included MiniGL, Warp3D, StormMesa (agl.library) and CyberGL. The Amiga was launched at a time when there was little support for 3D graphics libraries to enhance desktop GUIs and computer rendering capabilities. However, the Amiga became one of the first widespread 3D development platforms. VideoScape 3D was one of the earliest 3D rendering and animation systems, and Silver/TurboSilver was one of the first ray-tracing 3D programs. Then Amiga boasted many influential applications in 3D software, such as Imagine, maxon's Cinema 4D, Realsoft 3D, VistaPro, Aladdin 4D and NewTek's Lightwave (used to render movies and television shows like Babylon 5). Likewise, while the Amiga is well known for its ability to easily genlock with video, it has no built-in video capture interface. The Amiga supported a vast number of third-party interfaces for video capture from American and European manufacturers. There were internal and external hardware solutions, called frame-grabbers, for capturing individual or sequences of video frames, including: Newtronic Videon, Newtek DigiView, Graffiti external framebuffer, the Digilab, the Videocruncher, Firecracker 24, Vidi Amiga 12, Vidi Amiga 24-bit and 24RT (Real Time), Newtek Video Toaster, GVP Impact Vision IV24, MacroSystem VLab Motion and VLab PAR, DPS PAR (Personal Animation Recorder), VHI (Video Hardware Interface) by IOSPIRIT GmbH, DVE-10, etc. Some solutions were hardware plug-ins for Amiga graphics cards like the Merlin XCalibur module, or the DV module built for the Amiga clone Draco from the German firm Macrosystem. Modern PCI bus TV expansion cards and their capture interfaces are supported through tv.library by Elbox Computer and tvcard.library by Guido Mersmann. Following modern trends in evolution of graphical interfaces, AmigaOS 4.1 uses the 3D hardware-accelerated Porter-Duff image composition engine. Audio Prior to version 3.5, AmigaOS only officially supported the Amiga's native sound chip, via audio.device. This facilitates playback of sound samples on four DMA-driven 8-bit PCM sound channels. The only supported hardware sample format is signed linear 8-bit two's complement. Support for third-party audio cards was vendor-dependent, until the creation and adoption of AHI as a de facto standard. AHI offers improved functionality, such as seamless audio playback from a user-selected audio device, standardized functionality for audio recording and efficient software mixing routines for combining multiple sound channels, thus overcoming the four-channel hardware limit of the original Amiga chipset. AHI can be installed separately on AmigaOS v2.0 and later. AmigaOS itself did not support MIDI until version 3.1, when Roger Dannenberg's camd.library was adapted as the standard MIDI API. Commodore's version of camd.library also included a built-in driver for the serial port. The later open source version of camd.library by Kjetil Matheussen did not provide a built-in driver for the serial port, but provided an external driver instead. AmigaOS was one of the first operating systems to feature speech synthesis with software developed by SoftVoice, Inc., which allowed text-to-speech conversion of American English. This had three main components: narrator.device, which modulates the phonemes used in American English, translator.library, which translates English text to American English phonemes using a set of rules, and a high-level SPEAK: handler, which allows command-line users to redirect text output to speech. A utility called Say was included with the OS, which allowed text-to-speech synthesis with some control of voice and speech parameters. A demo was also included with AmigaBASIC programming examples. Speech synthesis was occasionally used in third-party programs, particularly educational software. For example, the word processors Prowrite and Excellence! could read out documents using the synthesizer. These speech synthesis components remained largely unchanged in later OS releases and Commodore eventually removed speech synthesis support from AmigaOS 2.1 onward because of licensing restrictions. Despite the American English limitation of the narrator.devices phonemes, Francesco Devitt developed an unofficial version with multilingual speech synthesis. This made use of an enhanced version of the translator.library which could translate a number of languages into phonemes, given a set of rules for each language. Storage The AmigaOS has a dynamically sized RAM disk, which resizes itself automatically to accommodate its contents. Starting with AmigaOS 2.x, operating system configuration files were loaded into the RAM disk on boot, greatly speeding operating system usage. Other files could be copied to the RAM disk like any standard device for quick modification and retrieval. Also beginning in AmigaOS 2.x, the RAM disk supported file-change notification, which was mostly used to monitor configuration files for changes. Starting with AmigaOS 1.3, there is also a fixed-capacity recoverable RAM disk, which functions as a standard RAM disk but can maintain its contents on soft restart. It is commonly called the RAD disk after its default device name, and it can be used as a boot disk (with boot sector). Previously, a recoverable RAM disk, commonly called the ASDG RRD or VD0, was introduced in 1987; at first, it was locked to ASDG expansion memory products. Later, the ASDG RRD was added to the Fred Fish series of freeware, shareware, and public domain software (disks 58 and 241). Scripting The AmigaOS has support for the Rexx language, called ARexx (short for "Amiga Rexx"), and is a script language which allows for full OS scripting, similar to AppleScript; intra-application scripting, similar to VBA in Microsoft Office; as well as inter-program communication. Having a single scripting language for any application on the operating system is beneficial to users, instead of having to learn a new language for each application. Programs can listen on an "ARexx port" for string messages. These messages can then be interpreted by the program in a similar fashion to a user pushing buttons. For example, an ARexx script run in an e-mail program could save the currently displayed email, invoke an external program which could extract and process information, and then invoke a viewer program. This allows applications to control other applications by sending data back and forth directly with memory handles, instead of saving files to disk and then reloading them. Since AmigaOS 4, the Python language is included with the operating system. Technical overview John C. Dvorak stated in 1996: Libraries and devices AmigaOS provides a modular set of system functions through dynamically-loaded shared libraries, either stored as a file on disk with a ".library" filename extension, or stored in the Kickstart firmware. All library functions are accessed via an indirect jump table, which is a negative offset to the library base pointer. That way, every library function can be patched or hooked at run-time, even if the library is stored in ROM. The core library of AmigaOS is the exec.library (Exec), which provides an interface to functions of the Amiga's microkernel. Device drivers are also libraries, but they implement a standardized interface. Applications do not usually call devices directly as libraries, but use the exec.library I/O functions to indirectly access them. Like libraries, devices are either files on disk (with the ".device" extension), or stored in the Kickstart ROM. Handlers, AmigaDOS and filesystems The higher-level part of device and resource management is controlled by handlers, which are not libraries, but tasks, and communicate by passing messages. One type of handler is a filesystem handler. The AmigaOS can make use of any filesystem for which a handler has been written, a possibility that has been exploited by programs like CrossDOS and by a few "alternative" file systems to the standard OFS and FFS. These file systems allow one to add new features like journaling or file privileges, which are not found in the standard operating system. Handlers typically expose a device name to the DOS, which can be used to access the peripheral (if any) associated with the handler. As an example of these concepts is the SPEAK: handler which could have text redirected to spoken speech, through the speech synthesis system. Device names are case insensitive (uppercase by convention) strings followed by a colon. After the colon a specifier can be added, which gives the handler additional information about what is being accessed and how. In the case of filesystem, the specifier usually consists of a path to a file in the filesystem; for other handlers, specifiers usually set characteristics of the desired input/output channel (for the SER: serial port driver, for example, the specifier will contain bit rate, start and stop bits, etc.). Filesystems expose drive names as their device names. For example, DF0: by default refers to the first floppy drive in the system. On many systems DH0: is used to refer to the first hard drive. Filesystems also expose volume names, following the same syntax as device names: these identify the specific medium in the file system-managed drive. If DF0: contains a disk named "Workbench", then Workbench: will be a volume name that can be used to access files in DF0:. If one wanted to access a file named "Bar" located in directory "Foo" of the disk with name "Work" in drive DF0:, one could write "DF0:Foo/Bar" or "Work:Foo/Bar". However, these are not completely equivalent, since when the latter form is used, the system knows that the wanted volume is''' "Work" and not just any volume in DF0:. Therefore, whenever a requested file on "Work" is being accessed without volume "Work" being present in any drive, it will say something to the effect of: Please insert volume Work in any drive. Programs often need to access files without knowing their physical location (either the drive or the volume): they only know the "logical path" of the file, i.e. whether the file is a library, a documentation file, a translation of the program's messages, and so on. This is solved in AmigaOS by the use of assigns. An assign follows, again, the same syntax as a device name; however, it already points to a directory inside the filesystem. The place an assign points to can be changed at any time by the user (this behavior is similar to, but nevertheless distinct from, the subst command in MS-DOS, for example). Assigns were also convenient because one logical assign could point to more than one different physical location at the same time, thereby allowing an assign′s contents to expand logically, while still maintaining a separate physical organization. Standard assigns that are generally present in an AmigaOS system include: SYS:, which points to the boot drive's root directory. C:, which points to a directory containing shell commands. At boot time, this is SYS:C, if it exists, otherwise SYS:. The command path defaults to C: and the current working directory, so putting executables in C: allows them to be executed simply by typing their name. DEVS:, which points to a directory containing the system's devices. At boot time, this is SYS:Devs if that directory exists, otherwise SYS:. L:, which points to a directory containing AmigaDOS handlers and filesystems. At boot time, this is SYS:L if it exists, otherwise L: is not automatically created. LIBS:, which points to a directory containing the system's libraries. At boot time, this is SYS:Libs if that directory exists, otherwise SYS:. S:, which points to a directory with scripts, including the startup-sequence which is executed automatically at boot time, if it exists. At boot time, this is SYS:S if it exists, otherwise S: is not automatically created. T:, which points to a temporary folder. PROGDIR:, a special assign that always points to the directory containing the currently running executable. So, if you run "SYS:Tools/Multiview" and "SYS:System/Format", PROGDIR: points at SYS:Tools for Multiview while simultaneously pointing at SYS:System for the Format command. This feature was introduced in Workbench 2.0. Memory paging and a swap partition in later versions AmigaOS 4 introduced new system for allocating RAM and defragmenting it "on the fly" during system inactivities. It is based on slab allocation method and there is also present a memory pager that arbitrates paging memory and allows the swapping of large portions of physical RAM on mass storage devices as a sort of virtual memory. Co-operative paging was finally implemented in AmigaOS 4.1. Versions Since the introduction of AmigaOS in 1985 there have been four major versions and several minor revisions. Up until release 3.1 of the Amiga's operating system, Commodore used Workbench to refer to the entire Amiga operating system. As a consequence Workbench was commonly used to refer to both the operating system and the file manager component. For end users Workbench was often synonymous with AmigaOS. From version 3.5 the OS was renamed "AmigaOS" and pre-3.5 versions were also retroactively referred to as "AmigaOS" (rather than Workbench). Subsequently, "Workbench" refers to the native graphical file manager only. From its inception, Workbench offered a highly customizable interface. The user could change the aspect of program icons replacing it with newer ones with different color combinations. Users could also take a "snapshot" of icons and windows so the icons will remain on the desktop at coordinates chosen by user and windows will open at the desired size. AmigaOS 1.0 – 1.4 AmigaOS 1.0 was released with the first Amiga, the Amiga 1000, in 1985. The 1.x versions of AmigaOS by default used a blue and orange color scheme, designed to give high contrast on even the worst of television screens (the colors can be changed by the user). Version 1.1 consists mostly of bug fixes and, like version 1.0, was distributed for the Amiga 1000 only. The display was highly customizable for the era. The user was free to create and modify system and user icons, which could be of arbitrary size and design and can have two image states to produce a pseudo-animated effect when selected. Users could customize four display colors and choose from two resolutions: or (interlaced) on NTSC, or or on PAL systems. In later revisions, the TV or monitor overscan could be adjusted. Several features were deprecated in later versions. For example, the gauge meter showing the free space on a file system was replaced with a percentage in AmigaOS 2.0 before being restored in 3.5. The default "busy" pointer (a comic balloon showing "Zzz...") was replaced with a stopwatch in later versions. AmigaOS 2.0, 2.1 AmigaOS 2.0 was released with the launch of the Amiga 3000 in 1990. Until AmigaOS 2.0 there was no unified look and feel design standard and application developers had to write their own widgets (both buttons and menus) if they wished to enhance the already-meager selection of standard basic widgets provided by Intuition. With AmigaOS 2.0 gadtools.library was created, which provided standard widget sets. The Amiga User Interface Style Guide, was published which explained how applications should be laid out for consistency. Intuition was improved with BOOPSI (Basic Object Oriented Programming System for Intuition) which enhanced the system with an object-oriented interface to define a system of classes in which every class individuates a single widget or describes an interface event. It can be used to program object oriented interfaces into Amiga at any level. AmigaOS 2.0 also added support for public screens. Instead of the AmigaOS screen being the only shareable screen, applications could create their own named screens to share with other applications. AmigaOS 2.0 rectified the problem of applications hooking directly into the input-events stream to capture keyboard and mouse movements, sometimes locking up the whole system. AmigaOS 2.0 provided Commodities, a standard interface for modifying or scanning input events. This included a standard method for specifying global "hotkey" key-sequences, and a Commodities Exchange registry for the user to see which commodities were running. AmigaOS 2.1 introduced AmigaGuide, a simple text-only hypertext markup scheme and browser, for providing online help inside applications. It also introduced Installer, a standard software installation program, driven by a LISP-like scripting language. AmigaOS 2.1 introduced multi-lingual locale support through locale.library and for the first time AmigaOS was translated to different languages. AmigaOS 3.0, 3.1 Version 3.0 was originally shipped with the Amiga 1200 and Amiga 4000 computers. Version 3.0 added datatypes support which allowed any application that supported datatypes to load any file format supported by datatypes. Workbench could load any background image in any format if the required datatype was installed. A tiny application called Multiview was included that could open and display any supported file. Its capabilities were directly related to the datatypes installed in Devs:Datatypes. The established AmigaGuide hypertext system gained more usability by using document links pointing to media files, for example pictures or sounds, all recognized by the datatypes. AmigaOS 3.5, 3.9 Around six years after AmigaOS 3.1 was released, following Commodore's demise, Haage & Partner were granted a license to update AmigaOS, which was released in 1999 as a software-only update for existing systems, that ran at least on a 68(EC)020 processor. The AmigaOS look and feel, though still largely based on the earlier 3.1 release was revised somewhat, with an improved user interface based on ReAction, improved icon rendering and official support for true color backdrops. These releases included support for existing third-party GUI enhancements, such as NewIcons, by integrating these patches into the system. The 3.5 and 3.9 releases included a new set of 256 color icons and a choice of desktop wallpaper. These replaced the default all-metal gray 4/8 color scheme used on AmigaOS from release 2.0 to 3.1. The 3.9 release of AmigaOS was again developed by Haage&Partner and released in 2000. The main improvements were the introduction of a program start bar called AmiDock, revised user interfaces for system settings and improved utility programs. AmigaOS 3.1.4, 3.2 In September 2018, Hyperion Entertainment released AmigaOS 3.1.4; this was both a software and hardware update for all Amigas. In 2019, AmigaOS 3.1.4.1 was released as a software only update to Amiga 3.1.4, mainly as a bug fix. It includes many fixes, modernizes several system components previously upgraded in OS 3.9, introduces support of larger hard drives (including at bootup), supports the entire line of Motorola 680x0 CPUs up to (and including) the Motorola 68060, and includes a modernized Workbench with a new, optional icon set. Unlike AmigaOS 3.5 / 3.9, AmigaOS 3.1.4 still supports the Motorola 68000 CPU. In May 2021, Hyperion Entertainment released AmigaOS 3.2, which includes all features of the previous version (3.1.4.1) and adds several new improvements such as support for ReAction GUI, management of Amiga Disk File images, help system and improved datatypes. AmigaOS 4.0, 4.1 This new AmigaOS, called AmigaOS 4.0 has been rewritten to become fully PowerPC compatible. It was initially developed on Cyberstorm PPC, as making it independent of the old Amiga chipsets was nontrivial. Since the fourth Developer Pre-Release Update a new technique was adopted and the screens are draggable in any direction. Drag and drop of Workbench icons between different screens is possible too. Also in AmigaOS 4.0 were a new version of Amidock, TrueType/OpenType fonts, and a movie player with DivX and MPEG-4 support. In AmigaOS 4.1, a new Start-up preferences feature was added which replaced the old WBStartup drawer. Additional enhancements were a new icon set to complement higher screen resolutions, new window themes including drop shadows, a new version of AmiDock with true transparency, scalable icons and AmigaOS with auto-update feature. Influence on other operating systems AROS Research Operating System (AROS) implements the AmigaOS API in a portable open-source operating system. Although not binary-compatible with AmigaOS (unless running on 68k), users have reported it to be highly source-code-compatible. MorphOS is a PowerPC native operating system which also runs on some Amiga hardware. It implements AmigaOS API and provides binary compatibility with "OS-friendly" AmigaOS applications (that is, those applications which do not access any native, legacy Amiga hardware directly just as AmigaOS 4.x unless executed on real Amiga models).pOS'' was a multiplatform closed-source operating system with source code-level compatibility with existing Amiga software. BeOS features also a centralized datatype structure similar to MacOS Easy Open after old Amiga developers requested Be to adopt Amiga datatype service. It allows the entire OS to recognize all kinds of files (text, music, videos, documents, etc.) with standard file descriptors. The datatype system provides the entire system and any productivity tools with standard loaders and savers for these files, without the need to embed multiple file-loading capabilities into any single program. AtheOS was inspired by AmigaOS, and originally intended to be a clone of AmigaOS. Syllable is a fork of AtheOS, and includes some AmigaOS- and BeOS-like qualities. FriendUP is a cloud based meta operating system. It has many former Commodore and Amiga developers and employees working on the project. The operating system retains several AmigaOS-like features, including DOS Drivers, mount lists, a TRIPOS based CLI and screen dragging. Finally, the operating system of the 3DO Interactive Multiplayer bore a very strong resemblance to AmigaOS and was developed by RJ Mical, the creator of the Amiga's Intuition user interface. See also Comparison of operating systems References External links CBM software Microkernel-based operating systems Microkernels Assembly language software 1985 software

Operating System (OS)

HDOS HDOS is an early microcomputer operating system, originally written for the Heathkit H8 computer system and later also available for the Heathkit H89 and Zenith Z-89 computers. The author was Heath Company employee Gordon Letwin, who later was an early employee of Microsoft and lead architect of OS/2. HDOS originally came with a limited set of system software tools, including an assembler, but many commercial and large set of freeware programs from HUG (Heath User Group) became available for it eventually. HDOS 2.0 is notable because it was one of the first microcomputer operating systems to use loadable device drivers to achieve a degree of device independence and extensibility. Device names followed the RSX-11-style convention of DKn: where the first two letters were the device driver file name and n was a number (DK0:, DK1:, and so on would all be handled by DK.SYS). Other similarities to RSX included the use of PIP for file transfer, and the use of EOT for file termination. Similar to how Heath/Zenith published complete schematics and part lists for its computers, the company sold to users the source code for HDOS. The full source paper listing is held at yesterpc.org, old computer museum. Item references (Heathkit part number) are HOS-1-SL part number 595–2466. Commands The following list of commands are supported by HDOS. BOOT BYE CAT COPY DATE DELETE DISMOUNT FLAGS HELP MOUNT ONECOPY PIP RENAME RUN SET STAT STATUS TYPE VER Versions HDOS 1.0 – written in 1978 by J. Gordon Letwin HDOS 1.5 – Gregg Chandler HDOS 1.6 – Gregg Chandler HDOS 2.0 – released in 1980, written by Gregg Chandler, released into the public domain in April 1988 HDOS 3.0 – released into the public domain in August 1986 HDOS 3.02 – enhanced version by Richard Musgrave See also Heathkit Zenith Data Systems List of operating systems References External links HeathDOS Michael A. Pechuria, Comparing Two Microcomputer Operating Systems: CP/M and HDOS. Communications of the ACM, March 1983, vol. 26, no. 3. Society of Eight-Bit Heathkit Computerists A web site dedicated to preserving the Heathkit 8-bit computers, source listing in PDF form Free software operating systems Public-domain software with source code 1978 software

Operating System (OS)

MOSIX MOSIX is a proprietary distributed operating system. Although early versions were based on older UNIX systems, since 1999 it focuses on Linux clusters and grids. In a MOSIX cluster/grid there is no need to modify or to link applications with any library, to copy files or login to remote nodes, or even to assign processes to different nodes – it is all done automatically, like in an SMP. History MOSIX has been researched and developed since 1977 at The Hebrew University of Jerusalem by the research team of Prof. Amnon Barak. So far, ten major versions have been developed. The first version, called MOS, for Multicomputer OS, (1981–83) was based on Bell Lab's Seventh Edition Unix and ran on a cluster of PDP-11 computers. Later versions were based on Unix System V Release 2 (1987–89) and ran on a cluster of VAX and NS32332-based computers, followed by a BSD/OS-derived version (1991–93) for a cluster of 486/Pentium computers. Since 1999 MOSIX is tuned to Linux for x86 platforms. MOSIX2 The second version of MOSIX, called MOSIX2, compatible with Linux-2.6 and 3.0 kernels. MOSIX2 is implemented as an OS virtualization layer that provides users and applications with a single system image with the Linux run-time environment. It allows applications to run in remote nodes as if they run locally. Users run their regular (sequential and parallel) applications while MOSIX transparently and automatically seek resources and migrate processes among nodes to improve the overall performance. MOSIX2 can manage a cluster and a multicluster (grid) as well as workstations and other shared resources. Flexible management of a grid allows owners of clusters to share their computational resources, while still preserving their autonomy over their own clusters and their ability to disconnect their nodes from the grid at any time, without disrupting already running programs. A MOSIX grid can extend indefinitely as long as there is trust between its cluster owners. This must include guarantees that guest applications will not be modified while running in remote clusters and that no hostile computers can be connected to the local network. Nowadays these requirements are standard within clusters and organizational grids. MOSIX2 can run in native mode or in a virtual machine (VM). In native mode, performance is better, but it requires modifications to the base Linux kernel, whereas a VM can run on top of any unmodified operating system that supports virtualization, including Microsoft Windows, Linux and Mac OS X. MOSIX2 is most suitable for running compute intensive applications with low to moderate amount of input/output (I/O). Tests of MOSIX2 show that the performance of several such applications over a 1 Gbit/s campus grid is nearly identical to that of a single cluster. Main features Provides aspects of a single-system image: Users can login on any node and do not need to know where their programs run. No need to modify or link applications with special libraries. No need to copy files to remote nodes. Automatic resource discovery and workload distribution by process migration: Load-balancing. Migrating processes from slower to faster nodes and from nodes that run out of free memory. Migratable sockets for direct communication between migrated processes. Secure run time environment (sandbox) for guest processes. Live queuing – queued jobs preserve their full generic Linux environment. Batch jobs. Checkpoint and recovery. Tools: automatic installation and configuration scripts, on-line monitors. MOSIX for HPC MOSIX is most suitable for running HPC applications with low to moderate amount of I/O. Tests of MOSIX show that the performance of several such applications over a 1 Gbit/s campus grid is nearly identical to that of a single cluster. It is particularly suitable for: Efficient utilization of grid-wide resources, by automatic resource discovery and load-balancing. Running applications with unpredictable resource requirements or run times. Running long processes, which are automatically sent to grid nodes and are migrated back when these nodes are disconnected from the grid. Combining nodes of different speeds, by migrating processes among nodes based on their respective speeds, current load, and available memory. A few examples: Scientific applications – genomic, protein sequences, molecular dynamics, quantum dynamics, nano-technology and other parallel HPC applications. Engineering applications – CFD, weather forecasting, crash simulations, oil industry, ASIC design, pharmaceutical and other HPC applications. Financial modeling, rendering farms, compilation farms. MOSIX4 MOSIX4 was released in July 2014. As of version 4, MOSIX doesn't require kernel patching. openMosix After MOSIX became proprietary software in late 2001, Moshe Bar forked the last free version and started the openMosix project on February 10, 2002. On July 15, 2007, Bar decided to end the openMosix project effective March 1, 2008, claiming that "the increasing power and availability of low cost multi-core processors is rapidly making single-system image (SSI) clustering less of a factor in computing". These plans were reconfirmed in March 2008. The LinuxPMI project is continuing development of the former openMosix code. Further reading MOSIX4 A. Barak and A. Shiloh. The MOSIX Cluster Management System for Distributed Computing on Linux Clusters and Multi-Cluster private Clouds white paper, 2016. A. Barak and A. Shiloh. MOSIX Administrator's, User's and Programmer's Guides and Manuals. Revised for MOSIX-4.3, 2015. MOSIX2 for Linux 2.6 Meiri E. and Barak A., Parallel Compression of Correlated Files, Proc. IEEE Cluster 2007, Austin, Sept. 2007. Amar L., Stosser J., Barak A. and Neumann D., Economically Enhanced MOSIX for Market-based Scheduling in Grid OS, Workshop on Economic Models and Algorithms for Grid System (EAMGS 2007), 8th IEEE/ACM Int. Conf. on Grid Computing(Grid 2007), Austin, Sept. 2007. Amar L., Barak A., Levy E. and Okun M., An On-line Algorithm for Fair-Share Node Allocations in a Cluster. Proc. 7-th IEEE Int. Symposium on Cluster Computing and the Grid (CCGrid '07), pp. 83–91, Rio de Janeiro, May 2007. Amar L., Barak A., Drezner Z. and Peer I., Gossip Algorithms for Maintaining a Distributed Bulletin Board with Guaranteed Age Properties. TR, 2006. Barak A., Shiloh A. and Amar L., An Organizational Grid of Federated MOSIX Clusters. Proc. 5-th IEEE International Symposium on Cluster Computing and Grid (CCGrid '05), Cardiff, May 2005 . Barak A. and Drezner Z., Gossip-Based Distributed Algorithms for Estimating the Average Load of Scalable Computing Clusters and Grids. Proc. 2004 Int. Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA'04), Las Vegas, NV, June 2004. MOSIX for Linux 2.2 & 2.4 Okun M. and Barak A., Atomic Writes for Data Integrity and Consistency in Shared Storage Devices for Clusters. Journal of Future Generation Computer Systems, Vol. 20, No. 4, pp. 539–547, May 2004. Amar L., Barak A. and Shiloh A., The MOSIX Direct File System Access Method for Supporting Scalable Cluster File Systems. Cluster Computing, Vol. 7, No. 2, pp. 141–150, April 2004. Keren A. and Barak A., Opportunity Cost Algorithms for Reduction of I/O and Interprocess Communication Overhead in a Computing Cluster. IEEE Tran. Parallel and Distributed Systems, Vol. 14, No. 1, pp. 39–50, January 2003. Amar L., Barak A. and Shiloh A., The MOSIX Parallel I/O System for Scalable I/O Performance. Proc. 14-th IASTED Int. Conference on Parallel and Distributed Computing and Systems (PDCS 2002), pp. 495–500, Cambridge, MA, Nov. 2002. Amir Y., Awerbuch B., Barak A., Borgstrom R.S. and Keren A., An Opportunity Cost Approach for Job Assignment in a Scalable Computing Cluster. IEEE Tran. on Parallel and Distributed Systems, Vol. 11, No. 7, pp. 760–768, July 2000. McClure S. and Wheeler R., MOSIX: How Linux Clusters Solve Real World Problems. Proc. 2000 USENIX Annual Tech. Conf., pp. 49–56, San Diego, CA., June 2000. Amar L., Barak A., Eizenberg A. and Shiloh A.,. The MOSIX Scalable Cluster File Systems for LINUX, June 2000. Barak A., La'adan O. and Shiloh A., Scalable Cluster Computing with MOSIX for LINUX. Proc. 5-th Annual Linux Expo, pp. 95–100, Raleigh, NC, May 1999. MOSIX Version 1 book Barak A., Guday S. and Wheeler R., The MOSIX Distributed Operating System, Load Balancing for UNIX. Lecture Notes in Computer Science, Vol. 672, Springer-Verlag, May 1993. Other Barak A. and La'adan O., The MOSIX Multicomputer Operating System for High Performance Cluster Computing. Journal of Future Generation Computer Systems, Vol. 13, No. 4-5, pp. 361–372, March 1998. Barak A., Laden O. and Yarom Y., The NOW MOSIX and its Preemptive Process Migration Scheme. IEEE TCOS, Vol. 7, No. 2, pp. 5–11, Summer 1995. Haban D., Wybranietz D. and Barak A., Monitoring and Management-Support of Distributed Systems, Proc. European Workshop on Progress in Distributed operating Systems and Distributed System management, pp. 110–137, Berlin, April 1989. Barak A. and Wheeler R., MOSIX: An Integrated Multiprocessor UNIX. Proc. Winter 1989 USENIX Conf., pp. 101–112, San Diego, CA, Feb. 1989. Barak A., Shiloh A. and Wheeler R., Flood Prevention in the MOSIX Load-Balancing Scheme, IEEE-TCOS Newsletter, Vol. 3, No. 1, pp. 24–27, Winter 1989. Barak A. and Kornatzky Y., Design Principles of Operating Systems for Large Scale Multicomputers, Proc. Int. Workshop on Experience with Distributed Systems, pp. 104–123, Kaiserslautern, Sept. 1987. Also, Report RC 13220, IBM T.J. Watson Research Center, Yorktown Heights, NY, Oct. 1987. Alon N., Barak A. and Manber U., On Disseminating Information Reliably Without Broadcasting, Proc. 7-th Int. Conf. on Distributed Computing Systems (ICDCS-7), pp. 74–81 (best conference paper), Berlin, Sept. 1987. Barel A., NSMOS - MOS Port to the National's 32000 Family Architecture. Proc. 2nd Israel Conf. Computer Systems and Soft. Eng., Tel-Aviv, May 1987. Barak A., Drezner Z. and Gurevich Y., On the Number of Active Nodes in a Multicomputer System, Networks, An Int. Journal, Vol. 16, No. 3, pp. 275–282, Fall 1986. Barak A. and Paradise G. O., MOS - Scaling Up UNIX. Proc. Summer 1986 USENIX Conf., pp. 414–418, Atlanta, GA, June 1986. Barak A. and Paradise G. O., MOS - a Load Balancing UNIX. Proc. Autumn 86 EUUG Conf., pp. 273–280, Manchester, Sept. 1986. Drezner Z. and Barak A., An Asynchronous Algorithm for Scattering Information Between the Active Nodes of a Multicomputer System, Journal of Parallel and Distributed Computing, Vol. 3, No. 3, pp. 344–351, Sept. 1986. Barak A. and Shiloh A., A Distributed Load-balancing Policy for a Multicomputer. Software - Practice & Experience, Vol. 15, No. 9, pp. 901–913, Sept. 1985. Barak A. and Litman A., MOS - A Multicomputer Distributed Operating System. Software - Practice & Experience, Vol. 15, No. 8, pp. 725–737, Aug. 1985. Drezner Z. and Barak A., Efficient Algorithms for Routing Information in a Multicomputer System, Distributed Algorithms on Graphs, Carleton Univ. Press, pp. 41–48, Ottawa, Aug. 1985. Barak A., Dynamic Process Control for Distributed Computing, Proc. 3-rd Int. Conf. on Distributed Computing Systems (ICDCS-3), pp. 36–40, Ft. Lauderdale, FL, Oct. 1982. Barak A., Shapir A., Steinberg G. and Karshmer A.I., A Modular, Distributed UNIX. Proc. 14-th Hawaii Int. Conf. on System Science, pp. 740–747, January 1981. Barak A. and Shapir A., UNIX with satellite Processors. Software - Practice & Experience, Vol. 10, No. 5, pp. 383–392, May 1980. See also LinuxPMI OpenMOSIX Notes External links MOSIX homepage Cluster computing Grid computing Internet Protocol based network software Parallel computing Distributed operating systems

Operating System (OS)

DOS Plus DOS Plus (erroneously also known as DOS+) was the first operating system developed by Digital Research's OEM Support Group in Newbury, Berkshire, UK, first released in 1985. DOS Plus 1.0 was based on CP/M-86 Plus combined with the PCMODE emulator from Concurrent PC DOS 4.11. While CP/M-86 Plus and Concurrent DOS 4.1 still had been developed in the United States, Concurrent PC DOS 4.11 was an internationalized and bug-fixed version brought forward by Digital Research UK. Later DOS Plus 2.x issues were based on Concurrent PC DOS 5.0 instead. In the broader picture, DOS Plus can be seen as an intermediate step between Concurrent CP/M-86 and DR DOS. DOS Plus is able to run programs written for either CP/M-86 or MS-DOS 2.11, and can read and write the floppy formats used by both of these systems. Up to four CP/M-86 programs can be multitasked, but only one DOS program can be run at a time. User interface DOS Plus attempts to present the same command-line interface as MS-DOS. Like MS-DOS, it has a command-line interpreter called COMMAND.COM (alternative name DOSPLUS.COM). There is an AUTOEXEC.BAT file, but no CONFIG.SYS (except for FIDDLOAD, an extension to load some field-installable device drivers (FIDD) in some versions of DOS Plus 2.1). The major difference the user will notice is that the bottom line of the screen contains status information similar to: DDT86 ALARM UK8 PRN=LPT1 Num 10:17:30 The left-hand side of the status bar shows running processes. The leftmost one will be visible on the screen; the others (if any) are running in the background. The right-hand side shows the keyboard layout in use (UK8 in the above example), the printer port assignment, the keyboard Caps Lock and Num Lock status, and the current time. If a DOS program is running, the status line is not shown. DOS programs cannot be run in the background. The keyboard layout in use can be changed by pressing , and one of the function keys –. Commands DOS Plus contains a number of extra commands to support its multitasking features: ADDMEM: Sets the amount of extra memory to allocate to EXE programs. ALARM: A message alarm clock. BACKG: Allows background processes to be listed and stopped. COMSIZE: Sets the amount of memory to allocate to COM programs. PRINT: Print spooler. SLICE: Sets the amount of processor time to give to the foreground program. See also the %$SLICE% environment variable. USER: Sets the user number to use when accessing CP/M media. It also contains subsets of the standard DOS commands and CP/M commands – for example, it has both a built-in COPY command, and a PIP utility, both of which copy files. The CD command can assign one of the three drives N:, O: or P: to a directory on a different drive, in a similar manner to the MS-DOS command SUBST. For example, CD N:=C:\DATA\ACCOUNTS will cause the directory C:\DATA\ACCOUNTS to appear as drive N:. This so-called floating drive feature allows old programs which don't support subdirectories to work under DOS Plus and can be used to make file handling at the command prompt much easier. This feature is also present in Concurrent DOS, Multiuser DOS, System Manager 7, and REAL/32, however, these systems extend the concept to all unused drive letters from A: to Z:, except for drive letter L:. DR DOS 3.31 – 6.0 (up to the November 1992 updates with BDOS 6.7 only) also support this (including drive letter L:). Under the later systems, the 4DOS/NDOS command processor supports this features as well. Floating drives are implemented in the BDOS kernel, not in the command line shell, thus this feature can also be used from within DOS applications when entering directory paths for as long as the application does not parse and split the dirspec for further processing. Using a similar feature, Concurrent DOS, Multiuser DOS, System Manager and REAL/32 will dynamically assign a floating drive L: to the load path of a loaded application, thereby allowing applications to refer to files residing in their load directory under a standardized drive letter instead of under a fixed absolute path. This load drive feature makes it much easier to move software installations on and across disks without having to adapt paths to overlays, configuration files or user data stored in the load directory or subsequent directories. (For similar reasons, the appendage to the environment block associated with loaded applications under MS-DOS/PC DOS 3.0 (and higher) contains a reference to the load path of the executable, however, this consumes more resident memory, and to take advantage of it, support for it must be coded into the executable, whereas DRI's solutions transparently works with any kind of application.) Another feature resulting from the BDOS' internal organization of current working directories as relative links to parent directories is the theoretically unlimited directory depth supported by all those above mentioned operating systems – in contrast to MS-DOS/PC DOS (and DR DOS since 1992), where an MS-DOS compatible internal data structure named Current Directory Structure (CDS) limits directory depths to a maximum of 66 characters. These features can be attributed to the fact that CP/M itself did not have a concept of subdirectories, and DOS was emulated under these operating systems, so directories had to be translated to internal CP/M structures in some intelligent way. Internal structure DOS Plus boots from a single file called either DOSPLUS.SYS or NETPLUS.SYS (rather than the IO.SYS / MSDOS.SYS combination of MS-DOS). This file is in the CP/M-86 CMD format, and is structured internally as a number of modules: The BDOS basic disk operating system kernel, which handles multitasking and implements the CP/M API. The XIOS extended input/output system, which is the machine-dependent component that performs low-level disc and character I/O. In the case of NETPLUS.SYS with DR Net support. The DOS emulator (internally named PCMODE), which converts each MS-DOS function call into one or more CP/M calls. In the case of a request to change the current directory, for example, this would translate to a series of 'open directory' calls, one for each directory in the path. A stub which loads COMMAND.COM (or DOSPLUS.COM) when required. This stub contains the string "OS=CPCDOS", suggesting that it is based on the Concurrent PC DOS codebase. Computers that used DOS Plus DOS Plus was the main operating system in ROM for the Philips :YES, for which it was originally developed. PC compatible versions were supplied with the Amstrad PC1512 and the Jasmin Turbo from the French company T.R.A.N. S.A. The non-IBM PC compatible BBC Master 512, came with DOS Plus 1.2, 1.2a or 2.1, also in conjunction with Solidisk's PC Plus memory expansion. There were DOS Plus 2.1e/g adaptations for the Apricot ACT series' non-standard 315 KB and 720 KB FAT12 floppy formats. The logical sectored FAT hard disk format (partition type ) of Sperry IT PCs, and the 80186 co-processor boards for the Acorn Archimedes A300 and A310 as well as Acorn 286 prototypes were supported as well. Versions Known operating system versions include: DOS Plus 1.0 (ROMed in Philips :YES) (with BDOS 4.1). DOS Plus 1.1 (with BDOS 4.1) DOS Plus 1.2 (with BDOS 4.1) DOS Plus 2.1 (with BDOS 5.0) See also Personal CP/M-86 2.0 (with BDOS 4.1) Personal CP/M-86 2.11 (with BDOS 4.1) CP/M-86 Plus MSX-DOS GEMDOS GEM XM Notes References Further reading External links http://bbc.nvg.org/doc/Master%20512%20Technical%20Guide/ CP/M variants Microcomputer software Disk operating systems Floppy disk-based operating systems Embedded operating systems ROM-based operating systems DOS variants Digital Research operating systems Discontinued operating systems Assembly language software 1985 software

Operating System (OS)

FunkOS FunkOS is a real-time operating system (RTOS) developed by Funkenstein Software Consulting, targeting a variety of microcontroller architectures. It is free to use in any project - commercial or otherwise - with few conditions. If the kernel is ported to a new target, that code must also be made available for inclusion in future releases. Also, if used in commercial projects, an attribution statement must be included in some form of product documentation. Description FunkOS is a fully preemptive multi-tasking environment, capable of running on a variety of modern microcontroller architectures. The kernel supports an unlimited number of program "tasks" running from up to 255 different priority levels. Tasks are independent programs, each with their own stack. At each RTOS tick, the highest-priority task is chosen for execution, with round-robin scheduling used when multiple tasks from the same priority level are ready to run. An idle task must be defined for every application, and can be used to invoke power-saving functionality of the hardware platform. Key features in the kernel include: Semaphores Mutex objects with Priority Inheritance Periodic lightweight threads Inter-process communications Task time quantum support for round-robin tasks Event queues Fixed-block dynamic memory allocation "Core Services" including a software real-time clock, and distributed computing support based on the concept of The Plumber Device driver HAL Task deadline monitoring (watchdog) module 2D display driver library supporting software rendering and hardware-acceleration GUI framework and widget library FAT16/32 read-only file system support Alternate C++ kernel (FunkOS++) Alternate round-robin only kernel (Pipsqueak) The kernel is highly customizable, allowing the developer to include or eliminate kernel features based on the application requirements. FunkOS is very lightweight as a result - the smallest useful kernel and application compiles to under 2 kilobytes of code space and 400 bytes of RAM on an AVR microcontroller. The FunkOS++ kernel is currently the only open-source, preemptive RTOS for 8-bit microcontrollers written in C++. It is supported by popular SSL/TLS libraries such as wolfSSL. Ports Atmel: AVR (ATmega, ATxmega) (ATmega328P, ATmega644, ATxmega256A1) Texas Instruments: MSP430 ARM: Cortex-M3 [untested] Ports for other modern microcontrollers are planned for future releases. Roadmap Future releases will include the following features: Virtual machine to enable hybrid native/virtual tasks Support for PIC24 and dsPIC architectures Stabilize the ARM Cortex-M3 port Bitmap font librarian application See also Embedded system, Single-board microcontroller Microcontroller, List of common microcontrollers Comparison of open-source operating systems References External links Computing platforms Real-time operating systems Embedded operating systems ARM operating systems

Operating System (OS)

Commodore DOS Commodore DOS, also known as CBM DOS, is the disk operating system used with Commodore's 8-bit computers. Unlike most other DOSes, which are loaded from disk into the computer's own RAM and executed there, CBM DOS is executed internally in the drive: the DOS resides in ROM chips inside the drive, and is run there by one or more dedicated MOS 6502 family CPUs. Thus, data transfer between Commodore 8-bit computers and their disk drives more closely resembles a local area network connection than typical disk/host transfers. CBM DOS versions At least seven distinctly numbered versions of Commodore DOS are known to exist; the following list gives the version numbers and related disk drives. Unless otherwise noted, drives are 5¼-inch format. The "lp" code designates "low-profile" drives. Drives whose model number starts with 15 connect via Commodore's unique serial IEEE-488 bus (IEC Bus) serial (TALK/LISTEN) protocols; all others use the parallel IEEE-488.   1.0 – found in the 2040 and 3040 floppy drives   2.0 – found in the 4040 and 3040 floppy drives   2.5 – found in the 8050 floppy drives   2.6 – found in the 1540, 1541 including the one built into the SX-64, 1551, 2031 (+"lp"), and 4031 floppy drives   2.7 – found in the 8050, 8250 (+"lp"), and SFD-1001 floppy drives   3.0 – found in the 1570, external 1571, and 8280 floppy drives (8280: 8-inch), as well as the 9060 and 9090 hard drives   3.1 – found in the built-in 1571 drive of C128DCR computers 10.0 – found in the 1581 (3½-inch) floppy drive Version 2.6 was by far the most commonly used and widely known DOS version, due to its use in the 1541 as part of C64 systems. Note: The revised firmware for the 1571 which fixed the relative file bug was also identified as V3.0. Thus it is not possible to differentiate the two versions using the version number alone. Technical overview 1541 directory and file types The 1541 Commodore floppy disk can contain up to 144 files in a flat namespace (no subdirectories); the directory is stored on reserved track 18, which is located halfway from the hub to the edge of a 35-track single-sided disk. A file name may be up to 16 bytes in length and is theoretically unique; by using direct access methods on the directory structure, it is possible to rename a file to that of another—although accessing such files may be difficult or impossible. Files with identical names usually serve no purpose except to inform or visually manage files. One popular trick, used, for example, by The Final Cartridge III, was to add files named "----------------" of type DEL< to the directory, and files could then be rearranged around those lines to form groups. Many game developers, warez group members, and demoscene hackers used some more clever custom directory entries as well. File names may contain a shifted space character ($A0), and if the directory listing is being viewed from BASIC, the portion of the file name beyond the $A0 character will appear to have been separated from the first part of the file name by a quotation mark, causing BASIC to not consider it to be part of the full file name. This feature can be used to create directory entries such as , which will then appear in the directory listing as, for example, . When the user moves the cursor to the beginning of the line, types the word LOAD over the file size, and presses , BASIC interprets that as , causing the program to be loaded into memory. Anything after the colon or the secondary address will not be executed, since the computer ignores any command after a LOAD. Alternatively, the user could press to and the program automatically. A null byte embedded in a file name will interrupt the listing after loading by BASIC. If there are three null bytes, that makes it difficult to list through BASIC. Many machine language programmers would experiment with null bytes in an attempt to make it harder for BASIC programmers to access their code and tamper with it. In BASIC, the directory can be accessed as a non-executable pseudo-BASIC program with (or in the case of a dual drive) followed by LIST. The first line has a line number of 0 or 1 (indicating the drive number), showing in reverse video the name and ID of the disk and a shorthand code for the DOS version with which it was created (codes vary only as far as the DOS versions use incompatible disk formats: "2A" is used by most 5.25-inch DOS versions, "3D" by the-3.5 inch 1581). Lines after this have the size of a file (in disk blocks) as their pseudo "line number", followed by the file name in quotes and the three-letter type code. The last line shows the number of unallocated blocks on the disk (again as a pseudo "line number"), followed by the words "BLOCKS FREE." On the Commodore 64, entering will flood the screen with garbage instead of loading the directory into BASIC RAM. This is because the drive assigns the directory a load address of $0401 (1025), which is equivalent to the start of BASIC for the Commodore PET, but corresponds to the default screen memory in the C64 (starting with the second character on the first line of the screen). Viewing the directory with a command overwrites the BASIC program in memory. The DOS Wedge and various third-party cartridges and extenders such as Epyx Fast Load, Action Replay, and The Final Cartridge III allow viewing of the disk directory using special commands that load the directory into screen memory without destroying the current BASIC program. Some versions of Commodore BASIC include a DIRECTORY or CATALOG command that performs the same function. The following file types are supported: SEQ A sequential file is a data file that can be linearly read from start to finish. SEQ files are commonly used to store documents or text files created by a word processor or other such editor. A sequential file is analogous to a flat file in Linux or UNIX, in that it has no specialized internal structure. It is not possible to position to any arbitrary location in a sequential file, as there is no analog of the lseek kernel call found in UNIX-like operating systems. PRG PRG files normally contain executable program code, although they can also be used for data files. The first two bytes of the PRG are read by the kernal "load file" routine and used to determine the load address (they are stored in a little endian format). REL A relative file is a variation of the sequential file type, in which an indexing mechanism referred to as side-sectors is present to permit record-oriented access. Records may be a maximum of 254 bytes in size and are addressed by a one-based cardinal number, permitting true random access to any part of the file. USR A user-specified file has an internal structure that is identical to that of a sequential file. Commodore's original purpose for this file type was the facilitation of DOS development, as the file content could be copied into a drive buffer for execution by the drive's microprocessor. Very few programs ever made use of this file type. Some applications that use non-standard low-level disk structures save data in USR format, which came to be considered a sort of "leave me alone, don't try to copy or delete" indication to the user. Most notably, GEOS' "VLIR" files show up as USR files. DEL An undocumented internally used file type similar in structure to a sequential file. Creation of this file type must be accomplished by direct manipulation of the disk directory. The presence of an asterisk (*) prepended to the file type in a directory listing (for example, *SEQ) indicates that the file was not properly closed after writing. When the drive is commanded to close a file that has been opened for writing, the associated buffer is flushed to the disk and the block availability map (BAM) is updated to accurately reflect which blocks have been used. If a program crash or other problem (such as the user removing the disk while a file is open) results in an "orphan file", also referred to as a "poison" or "splat" file, buffers are not flushed and the BAM will not accurately reflect disk usage, putting the disk at risk of corruption. A poison file generally cannot be accessed (but can be opened in "modify" mode), and an attempt to use the DOS scratch command to delete the file may cause filesystem corruption, such as crosslinking. The only practical method of removing one of these files is by opening the file in "modify" mode (and fixing it), or by validating the disk (see the DOS validate command below), the latter which rebuilds the BAM and removes poison file references from the directory. The infamous save-with-replace bug could result in creation of splat files. *DEL is a special type written into the on-disk directory entry of files that have been deleted. Such files are not shown in a normal directory listing, and their data blocks and directory entries will be reused by files that are subsequently created. Some utility programs allow the "un-deletion" of such files if their data blocks and directory entries haven not yet been overwritten by other files. DEL files are commonly used to insert banners or comment sections into a directory listing. File types with < after them (for example, PRG<) are "locked", and cannot be deleted—they can be opened for reading, however. There is no Commodore DOS command that can explicitly set or clear this status, but many third-party utilities were written to allow this to be done. These utilities generally read the directory using direct-access commands, perform the necessary modifications to the raw data, and then write the changes back to the disk. File access Accessing files is primarily an issue for the host computer. The kernal ROM in the computer contains the necessary primitive routines needed to access files, and the BASIC ROM contains a higher level abstraction for file access using BASIC syntax. The components that concern the DOS itself are file name parsing and the secondary address. This section will give an overview of the necessary BASIC commands for the sake of completeness. Opening a file on a Commodore disk unit entails the processing of a number of parameters that are vaguely analogous to file opening procedures in other environments. Since the DOS is actually running in the drive's controller, the file opening sequence must pass enough information to the drive to assure unambiguous interpretation. A typical statement in BASIC to write to a sequential file would be as follows: The parameters following the OPEN verb are as follows: 3 This parameter, the file number, logically identifies the opened file within the computer's operating system and is analogous to a file descriptor in UNIX-like operating systems. It is never sent to the drive and thus is neither known nor used by the drive's own operating system. The file number may be in the range of 1 to 254 inclusive, is assigned by the programmer and must be unique if more than one file is simultaneously opened. Once the file has been opened all program input and output procedures use the file number. In assembly language programs, this value is often referred to as LA (logical address), the abbreviation coming from the mnemonic that refers to the memory location where the file number is stored. File numbers greater than 127 cause the system to write an extra line feed after each carriage return (useful for double spacing a document, as an example.) 8 This parameter, the device number, identifies a specific peripheral attached to the computer. Devices 0 through 3 address the keyboard, tape cassette, RS-232 interface, and video display, respectively, all of which are directly controlled by the kernal ROM. Device numbers 4 and higher address devices attached to the peripheral bus, such as printers or disk drives. In the case of a disk drive, the device number refers to the unit's controller, not the drive mechanism(s) within the unit. By convention, the first disk drive unit on a system has device number 8, the second drive, if present, 9, etc., up to a maximum number of 15 (when eight disk drives are attached). The device number scheme was derived from the IEEE-488 (or general purpose interface GPIB) bus that was used with the Commodore PET/CBM models. In assembly language programs, this value is often referred to as FA or PA (physical address), again from the mnemonic for the memory location where the device number is stored. 4 This parameter, the secondary address, which may range from 0 to 15 inclusive, refers to a specific communication channel established with the device's controller and is passed to the device when it is commanded to "talk" or "listen" on the peripheral bus. As with the file number, the secondary address is determined by the programmer and must be unique for the device in question. The range 0 to 14 inclusive is used for passing data to or from the device, whereas 15, referred to as the "command channel", is used to issue commands to the device's controller (such as to rename a disk file), if the device is able to support such an operation. In disk drives, secondary addresses 0 to 14 inclusive are mapped to buffers within the controller, hence establishing communication with a specific file on a specific disk; since as mentioned above the drive does not know about the file number, it can only use the secondary address to make a difference between several files that are open at the same time. On the other hand, the host operating system is agnostic about the secondary address; it is transmitted to the drive on every access to the file, but not otherwise used by the host. In assembly language programs, this value is often referred to as SA (secondary address). COMMAND STRING The "0:ADDRESSBOOK,S,W" parameter is officially referred to in Commodore documentation as the command string and is interpreted by the controller of the device being accessed. In the case of a disk drive unit, the formal command string structure consists of the drive mechanism number (0:, not to be confused with the device number), filename (ADDRESSBOOK), file type (S, sequential in this example) and access mode (W, opened for writing in this example). In practice, some of these parameters may be omitted. Minimally, only the filename is required if the file is to be opened for reading. The drive number identifies a drive mechanism attached to a disk unit's controller and is analogous to a logical unit number in a SCSI controller that is capable of controlling multiple mechanisms (e.g., the OMTI SASI controllers that were developed to work with ST-412/ST-506 hard drives in the 1980s). In floppy disk units, the first mechanism is drive 0: and the second is 1:. It is fairly common practice to omit the drive number when communicating with a single drive floppy unit, as 0: is the default in such units, but since omitting the number can trigger a few obscure bugs in the DOS it is not a recommended practice (a colon alone is equivalent to 0: and is enough to avoid those bugs). An exception to this convention is with the Lt. Kernal hard disk subsystem, in which the drive number refers to "logical units" (virtual drives created on a single physical drive), which made syntax such as 4: or 10: necessary if a file to be opened was not on logical unit zero (equivalent to drive mechanism zero in a dual floppy unit). Files can also be loaded and saved to with LOAD and SAVE commands. File name specifiers can also be used here, for example, saves the BASIC program to a PRG (program) file and saves the BASIC program to a sequential file. If the secondary address isn't specified or is specified as 0 (e.g. ), the file is saved/loaded from the BASIC memory area (which, on the C64, starts by default at $0801). If the secondary address is specified as a non-zero value (e.g. ), the program is loaded starting from the address specified by the file itself (the PRG header, which is the first two bytes of the file)—this form of command is more common when loading machine code programs. Load relocation was first introduced on the VIC-20 because this machine could start BASIC RAM in several different locations, depending on the memory expansion that was installed. The older Commodore PET series did not support relocation, so and would have the same effect: the file would be loaded into the same memory region from which it was saved. Load relocation happens in the host, being an exception to what is said above about the secondary address being used only device-internally. Since the PET cannot relocate files, BASIC programs written on later Commodore machines must be modified by using a sector editor to change the header bytes. It is also possible to use the PET's built-in machine language monitor to change the link address for the BASIC program after loading it. The command will load the first program on the disk starting from the file-specified memory location. This is one of the most popular load commands of the platforms, the method to start majority of commercial software, for example. Of note is the fact that the wildcard expansion will only pick the first catalog name when no other file on that disk has been accessed before; the name of the last-used file is kept in memory, and subsequent commands will load that file rather than the first. (However, or will always load the first file on the disk.) The directories of disks in two-drive units are accessed as and . "0:$" and "1:$" do not access the directory but actual files on one drive or the other that just happen to be named "$". Partial directories can be loaded by adding a colon and a template: for example, would load a partial directory that shows only the files whose name starts with the letter K and which are of type PRG; all such partial directories still contain the initial disk name line and the final "BLOCKS FREE" line. The save-with-replace bug Commodore DOS also offers a "Save-with-Replace" command, which allows a file to be saved over an existing file without the need to first SCRATCH the existing file. This was done by prepending an @ symbol to the file name during the OPEN or SAVE operation - for instance, . For years rumors spread, beginning with the 4040 drive, of a bug in the command's implementation. At first, this was denied by some commentators. Prizes were offered to prove the existence of the bug. By early 1985 Compute! magazine advised readers to avoid using the command. That year various authors independently published articles proving that the Save-with-Replace bug was real and including methods by which it could be triggered. Affected devices included the single-drive 1541 and dual-drive 4040; the 8050 and 8250 did not exhibit the issue. Some commentators suggested the bug could be avoided by always explicitly specifying the 0: drive number when saving, though it was later shown that any disk operations without a drive number were sufficient to lead to the bug. The bug stemmed from the fact that the affected DOS implementations were modified versions of the DOS contained in earlier Commodore PET dual drives such as the 8050. This created a "phantom drive 1:" on single-drive systems, resulting in the allocation of an unnecessary buffer under some conditions. Since the Save-with-Replace command used all five drive buffers, and because the method by which the "phantom" buffer was allocated did not meet specifications, this resulted in scrambled data being written to the disk under some conditions. In September 1986, Philip A. Slaymaker published an article describing in great detail the cause of the bug and providing patches to the 1541 drive ROMs; readers with an EPROM burner could produce their own patched ROMs which could be swapped into the drive. Commodore was made aware of Slaymaker's findings, and while they never issued an official update for the original 1541's ROMs, they did fix the bug in Revision 5 of the 1571 ROMs, and also in the ROMs for the 1541-c and 1541-II drives. Although not supported by Commodore, it is known that the 1541-II firmware (but not that of the 1541-c) can also be used in an original 1541 drive by using EPROMs, which will fix the bug for that drive as well. Command channel As previously noted, the Commodore DOS itself is accessed via the "command channel", using syntax like that used to access files. Issuing commands to the DOS and retrieving status and error messages generated in response to commands is accomplished by opening a file to the device using 15 as the secondary address, for example: To retrieve and display the device status, one could code: In the above example, E will hold the error number (if any, it will be zero if no error exists), E$ will be a terse text description of the error, T will represent the disk track where the error occurred, and S will be the sector on track T to which the error refers. If no error exists, the equivalent of will be returned in the four variables. Note that INPUT# is a run mode only verb. Also, in programs that issue many disk commands it is customary to open a file to the device's command channel at the start of the program and not close it until the program has finished. Commodore BASIC versions 4.0 and later provide a pseudo-variable referred to as DS$ that may be used to retrieve drive status in lieu of the above code. This reserved variable is not available on earlier versions of BASIC, so the command channel must be manually read as demonstrated above. Note that immediately after power-on or reset, the DOS revision will be returned. For example, a 1541 will return . Error code 73 is common to all drive models and may be used to determine if the drive has been reset to its power-on state. DOS commands There are also a command for seeking in RELative type files (RECORD#), several block-level direct-access commands (BLOCK-READ, BLOCK-WRITE, BUFFER-POINTER), block management (BLOCK-ALLOCATE, BLOCK-FREE), drive memory manipulation and execution of program code on the drive's processor (MEMORY-WRITE, MEMORY-READ, MEMORY-EXECUTE, BLOCK-EXECUTE) and user-definable functions (USER and & commands). Some of the theoretically user-definable functions were rededicated for accessing new functionality in DOS versions after 1.0. References Notes Immers, Richard; Neufeld, Gerald G. (1984). Inside Commodore DOS. The Complete Guide to the 1541 Disk Operating System. DATAMOST, Inc & Reston Publishing Company, Inc. (Prentice-Hall). . Englisch, Lothar; Szczepanowski, Norbert (1984). The Anatomy of the 1541 Disk Drive. Grand Rapids, MI: Abacus Software (translated from the original 1983 German edition, Düsseldorf: Data Becker GmbH). . Lundahl, Reijo (1986). 1541-Levyasema. Amersoft. Commodore 64 software Commodore VIC-20 software Commodore DOS

Operating System (OS)

Advanced Comprehensive Operating System Advanced Comprehensive Operating System (ACOS) is a family of mainframe computer operating systems developed by NEC for the Japanese market. It consists of three systems, based on the General Comprehensive Operating System family developed by General Electric, Honeywell, and Bull. Two of these systems, ACOS-2 (based on GCOS 4) and ACOS-4 (based on GCOS 7) are still sold, although only ACOS-4 is under active development. ACOS-6 (based on GCOS 8) is an obsolete high-end mainframe platform, which ceased active development in the early 2000s. The first two models in NEC's SX series of supercomputers, the SX-1 and the SX-2 (released in 1985), ran an operating system derived from ACOS-4, which was variously called either SX-OS or SXCP (SX System Control Program). However, subsequent SX supercomputers, starting with the SX-3 (released in 1990), instead ran a derivative of Unix. In late September 2012, NEC announced a return from IA-64 to the previous NOAH line of proprietary mainframe processors for ACOS-4, now produced in a quad-core variant on 40 nm, called NOAH-6. ACOS-2 runs on Intel Xeon servers. See also Timeline of operating systems References External links ACOS Club home page ACOS-4 home page ACOS-2 home page ACOS Roadmap A history of GE/Honeywell/NEC/Bull operating systems Proprietary operating systems Computing platforms NEC software Mainframe computers Mainframe computer software

Operating System (OS)

System 2 System Two, System II or System 2 may refer to: Computing Acorn System 2, the early microcomputer Atari System 2, the arcade game platform by Atari Apple System 2, the operating system version for the Apple Macintosh Capcom System 2, an arcade system board in the 1990s Cromemco System Two, a computer system by Cromemco from 1978 Channel F System II, game console by Fairchild Digital Access Signalling System 2, the protocol by British Telecom Global File System 2, the file system by Red Hat Master System II, the 8-bit video game console by Sega Namco System 2, the arcade system board by Namco Sega System 2, an arcade system board in the 1990s S2 (programming language), style system 2 Other System 2 in Trilogy, an album from rock band Angeldust Super System 2, the poker system System Shock 2, the computer game See also Operating System/2 by IBM Personal System/2 by IBM

Operating System (OS)