MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

for x86-based

personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tech ...

s mostly developed by

Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation producing Software, computer software, consumer electronics, personal computers, and related services headquartered at th ...

. Collectively, MS-DOS, its rebranding as

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. It was manufactured and sold by IBM from the early 1980s into the 2000s. Developed by Microsoft, it was also ...

, and a 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 compatible IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones ...

s during the 1980s, from which point it was gradually superseded by operating systems offering a

graphical user interface The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows User (computing), users to Human–computer interaction, interact with electronic devices through graphical icon (comp ...

(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 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-DO ...

, 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 The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allow ...

processors running on computer hardware using

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined ...

s 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 A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming l ...

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 86-DOS (known internally as QDOS, for Quick and Dirty Operating System) is a discontinued operating system developed and marketed by Seattle Computer Products (SCP) for its Intel 8086-based computer kit. 86-DOS shared a few of its commands wi ...

owned by

Seattle Computer Products Seattle Computer Products (SCP) was a Tukwila, Washington, microcomputer hardware company which was one of the first manufacturers of computer systems based on the 16-bit Intel 8086 processor. SCP began shipping its first S-100 bus 8086 CPU ...

, written by

Tim Paterson Tim Paterson (born 1 June 1956) is an American computer programmer, best known for creating 86-DOS, an operating system for the Intel 8086. This system emulated the application programming interface (API) of CP/M, which was created by Gary K ...

. Development of 86-DOS took only six weeks, as it was basically a clone of

Digital Research Digital Research, Inc. (DR or DRI) was a company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser DOS, DOS Plus, DR DOS ...

's CP/M (for 8080/Z80 processors), ported to run on

8086 The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allo ...

processors and with two notable differences compared to CP/M: an improved disk sector buffering logic, and the introduction of

FAT12 File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by ...

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 The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a tea ...

, 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 PC or pc may refer to: Arts and entertainment * Player character or playable character, a fictional character controlled by a human player, usually in role-playing games or computer games * ''Port Charles'', an American daytime TV soap opera * ...

1.0 as one of three operating systems for the IBM 5150 or the

IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a tea ...

. 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 DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicati ...

), 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 An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...

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 ompatiblemachine. Some machines, like the

Tandy 2000 The Tandy 2000 is a personal computer introduced by Radio Shack in September 1983 based on the 8 MHz Intel 80186 microprocessor running MS-DOS. By comparison, the IBM PC XT (introduced in March 1983) used the older 4.77 MHz Intel 80 ...

, 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 Hardware abstractions are sets of routines in software that provide programs with access to hardware resources through programming interfaces. The programming interface allows all devices in a particular class ''C'' of hardware devices to be acce ...

). 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 Multi-user software is computer software that allows access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving ...

support from MS-DOS because Microsoft's

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

-based operating system,

Xenix Xenix is a discontinued version of the Unix operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s. The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and ...

, 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 The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sect ...

Zilog Z8000 The Z8000 ("''zee-'' or ''zed-eight-thousand''") is a 16-bit microprocessor introduced by Zilog in early 1979. The architecture was designed by Bernard Peuto while the logic and physical implementation was done by Masatoshi Shima, assisted by a ...

, and the

LSI-11 The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, ...

; they would be upwardly compatible with Xenix, which ''

Byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...

'' 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 Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

-derived operating system", and promising easy porting between them. After the

breakup of the Bell System The breakup of the Bell System was mandated on January 8, 1982, by an agreed consent decree providing that AT&T Corporation would, as had been initially proposed by AT&T, relinquish control of the Bell Operating Companies, which had provided lo ...

, however,

AT&T Computer Systems AT&T Computer Systems is the generic name for American Telephone & Telegraph's unsuccessful attempt to compete in the computer business. In return for divesting the local Bell Operating Companies ( Baby Bells), AT&T was allowed to have an unregul ...

started selling

UNIX System V Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...

. 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 The Santa Cruz Operation, Inc. (usually known as SCO, pronounced either as individual letters or as a word) was an American software company, based in Santa Cruz, California, that was best known for selling three Unix operating system variants ...

(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 Source-available software is software released through a source code distribution model that includes arrangements where the source can be viewed, and in some cases modified, but without necessarily meeting the criteria to be called open-source ...

, but not

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

as defined by

Open Source Initiative The Open Source Initiative (OSI) is the steward of the Open Source Definition, the set of rules that define open source software. It is a California public-benefit nonprofit corporation, with 501(c)(3) tax-exempt status. The organization w ...

Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed under copyleft ("s ...

standards. (NB. While the publishers claim this would be MS-DOS 1.1 and 2.0, it actually is SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11.) (NB. While the author claims this would be MS-DOS 1.1 and 2.0, it actually is SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11.) (NB. While the author claims this would be MS-DOS 1.1 and 2.0, it actually is SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11.) Microsoft would later re-license the code under the

MIT License The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license co ...

on September 28, 2018, making these versions

free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, ...

. As an

April Fool's Day April Fools' Day or All Fools' Day is an annual custom on 1 April consisting of practical jokes and hoaxes. Jokesters often expose their actions by shouting "April Fools!" at the recipient. Mass media can be involved in these pranks, which may b ...

joke in 2015,

Microsoft Mobile Microsoft Mobile was a subsidiary of Microsoft involved in the development and manufacturing of mobile phones. Based in Espoo, Finland, it was established in 2014 following the acquisition of Nokia's Devices and Services division by Microsoft in ...

launched a

Windows Phone Windows Phone (WP) is a discontinued family of mobile operating systems developed by Microsoft for smartphones as the replacement successor to Windows Mobile and Zune. Windows Phone featured a new user interface derived from the Metro design lan ...

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 Lifeboat Associates was a New York City company that was one of the largest microcomputer software distributors in the late 1970s and early 1980s. Lifeboat acted as an independent software broker marketing software to major hardware vendors such ...

"Software Bus 86" a.k.a.

SB-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 a few oper ...

, COMPAQ-DOS, NCR-DOS or

Z-DOS Z-DOS is a discontinued OEM version of Microsoft's MS-DOS specifically adapted to run on the hardware of the Zenith Z-100 personal computer. Overview The Z-100 used a 8086-family microprocessor, (the Intel 8088), but otherwise had a completely ...

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

. (Competitors released compatible DOS systems such as

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-DO ...

and

PTS-DOS PTS-DOS (aka PTS/DOS) is a disk operating system, a DOS clone, developed in Russia by PhysTechSoft and Paragon Technology Systems. History and versions PhysTechSoft was formed in 1991 in Moscow, Russia by graduates and members of MIPT, i ...

that could also run MS-DOS applications.) In the former

Eastern bloc The Eastern Bloc, also known as the Communist Bloc and the Soviet Bloc, was the group of socialist states of Central and Eastern Europe, East Asia, Southeast Asia, Africa, and Latin America under the influence of the Soviet Union that existed du ...

, MS-DOS derivatives named DCP () 3.20 and 3.30 (DCP 1700, DCP 3.3) and WDOS existed in the late 1980s.
/ref> They were produced by the

East German East Germany, officially the German Democratic Republic (GDR; german: Deutsche Demokratische Republik, , DDR, ), was a country that existed from its creation on 7 October 1949 until its dissolution on 3 October 1990. In these years the state ...

electronics manufacturer

VEB Robotron VEB Kombinat Robotron (or simply Robotron) was the biggest East German electronics manufacturer. It was based in Dresden and employed 68,000 people (1989). It produced personal computers, SM EVM minicomputers, the ESER mainframe computers, sev ...

. 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

Leading Edge Model D Boot Disk for MS-DOS 2

Support for IBM's XT 10 MB hard disk drives, support up to 16 MB or 32 MB

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 Inc., formerly ITT Corporation, is an American worldwide manufacturing company based in Stamford, Connecticut. The company produces specialty components for the aerospace, transportation, energy and industrial markets. ITT's three businesse ...

ITT-DOS 2.11 Version 2 (MS-DOS 2.11 for the ITT XTRA Personal Computer); Release date: July 1985 ** Olivetti M19 came with MS-DOS 2.11 ** Tandy 1000 HX has MS-DOS 2.11 in ROM **

TeleVideo TeleVideo Corporation was a U.S. company that achieved its peak of success in the early 1980s producing computer terminals. TeleVideo was founded in 1975 by K. Philip Hwang, a Utah State University, Hanyang University graduate born in South K ...

PC DOS 2.11, a TeleVideo OEM version of MS-DOS 2.11 **

Toshiba , commonly known as Toshiba and stylized as TOSHIBA, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. Its diversified products and services include power, industrial and social infrastructure systems ...

MS-DOS 2.11 in ROM drive for the model T1000 laptop * 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 File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by c ...

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 In computing, XCOPY is a command used on IBM PC DOS, MS-DOS, IBM OS/2, Microsoft Windows, FreeDOS, ReactOS, and related operating systems for copying multiple files or entire directory trees from one directory to another and for copying files a ...

. * Version 3.10 (OEM,

Multitech Acer Inc. ( ) is a Taiwanese multinational hardware and electronics corporation specializing in advanced electronics technology, headquartered in Xizhi, New Taipei City. Its products include desktop PCs, laptop PCs ( clamshells, 2-in-1s, c ...

); 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)Confirmed that there was Compaq Personal Computer DOS 3.31 aside from MS-DOS 3.31. – supports

FAT16B File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by ...

with partitions larger than 32 MiB;Up to 512 MB only. 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 alsoOnly if boot record of source floppy disk contains volume serial number 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)

History

Versions

MS-DOS 1.x

MS-DOS 2.x

MS-DOS 3.x

MS-DOS 4.0 / MS-DOS 4.x

MS-DOS 5.x