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 services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

for

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...

-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 tec ...

s mostly developed by

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

. 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 users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

(GUI), in various generations of the graphical

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

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-D ...

, 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 (allowi ...

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 w ...

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 ...

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 wit ...

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 bo ...

, 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 Kild ...

. 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 and ...

CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initial ...

(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 (allowi ...

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 team ...

, 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 team ...

. 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

, 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 communicatio ...

), 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 8088 pr ...

, 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 t ...

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, and ot ...

-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 Sector ...

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, and ot ...

-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 loc ...

, 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 unregulat ...

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 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 w ...

and a mixture of

Altos MS-DOS 2.11 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 ...

and

TeleVideo PC DOS 2.11 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 ...

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).html" ;"title="110. - 6910./ref> is a type o ...

Free Software Foundation The Free Software Foundation (FSF) is a 501(c)#501(c)(3), 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 ...

standards. (NB. While the publishers claim this would be MS-DOS 1.1 and 2.0, it actually is

and a mixture of

and

.) (NB. While the author claims this would be MS-DOS 1.1 and 2.0, it actually is

and a mixture of

and

.) (NB. While the author claims this would be MS-DOS 1.1 and 2.0, it actually is

and a mixture of

and

.) 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 comp ...

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, no ...

. 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 ...

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 i ...

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 la ...

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 suc ...

"Software Bus 86" a.k.a. SB-DOS,

COMPAQ-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 ...

NCR-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 ...

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 di ...

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, infor ...

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

::* 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 ANSI.SYS is a device driver in the DOS family of operating systems that provides extra console functions through ANSI escape sequences. It is partially based upon a subset of the text terminal control standard proposed by the ANSI X3L2 Technical C ...

. * 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 businesses ...

ITT-DOS 2.11 Version 2 (MS-DOS 2.11 for the ITT XTRA Personal Computer); Release date: July 1985 **

Olivetti M19 The Olivetti M19 was a personal computer made in 1986 by the Italian company Olivetti. It has an 8088 at 4.77 or 8 MHz and 256–640 KB of RAM. The BIOS is Revision Diagnostics 3.71. In the UK, it was sold by Acorn Computers as the A ...

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 Kore ...

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 system ...

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 Toshiba Pasopia 16 or PA7020 (also known as T300 in the U.S. and PAP in Europe) is an IBM PC compatible computer from manufacturer Toshiba, released in 1982 and based around a Intel 8088-2 microprocessor running at 6 MHz. Details The ope ...

)

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 disk drive, hard disks and other devices. It is often supported for compatibi ...

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 The HP 95LX Palmtop PC (F1000A, F1010A), also known as ''project Jaguar'', was Hewlett Packard's first MS-DOS-based pocket computer, or personal digital assistant, introduced in April 1991 in collaboration with Lotus Development Corporation. ...

) * 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 c ...

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) MS-DOS 4.0 was a multitasking release of MS-DOS developed by Microsoft based on MS-DOS 2.0. Lack of interest from OEMs, particularly IBM (who previously gave Microsoft multitasking code on IBM PC DOS included with TopView), led to it being rel ...

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 In computing, FASTOPEN is a DOS terminate-and-stay-resident command, introduced in MS-DOS version 3.3, that provides accelerated access to frequently-used files and directories. The command is also available in SISNE plus. Overview The command wo ...

/FASTSEEK,

DOSSHELL DOS Shell is a file manager that debuted in MS-DOS and PC DOS version 4.0, released in June 1988. It was discontinued in MS-DOS version 6.22, but remained part of the Supplemental Disk. The Supplemental Disk could be ordered or could be do ...

, could use EMS for the disk buffers and provided EMS drivers and emulation for

386 __NOTOC__ Year 386 ( CCCLXXXVI) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Honorius and Euodius (or, less frequently, year 113 ...

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)

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 An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standa ...

to partitions over 32 MB. First version to get the

HIMEM.SYS HIMEM.SYS is a DOS device driver which allows DOS programs to store data in extended memory according to the Extended Memory Specification (XMS). The memory beyond the first 1 MB of address space is required by Windows 9x/ Me in order to load ...

driver and load portions of the operating system into the

upper memory area In DOS memory management, the upper memory area (UMA) refers to memory between the addresses of 640 KB and 1024 KB ( 0xA0000–0xFFFFF) in an IBM PC or compatible. IBM reserved the uppermost 384 KB of the 8088 CPU's 1024 KB ...

and

high memory area In DOS memory management, the high memory area (HMA) is the RAM area consisting of the first 65520 bytes above the one megabyte in an IBM AT or compatible computer. In real mode, the segmentation architecture of the Intel 8086 and subsequen ...

. Support up to four DOS

primary partition Disk partitioning or disk slicing is the creation of one or more regions on secondary storage, so that each region can be managed separately. These regions are called partitions. It is typically the first step of preparing a newly installed disk, ...

s although

FDISK In computing, the fdisk command-line utility provides disk-partitioning functions, preparatory to defining file systems. fdisk features in the DOS, DR FlexOS, IBM OS/2, and Microsoft Windows operating systems, and in certain ports of FreeBS ...

cannot create more than one. ** AST Premium Exec DOS 5.0 (OEM) a version for the

AST Premium Exec AST Research, Inc., later doing business as AST Computer, was a personal computer manufacturer. It was founded in 1980 in Irvine, California by Albert Wong, Safi Qureshey, and Thomas Yuen, as an initialism of their first names. In the 1980s, AS ...

series of notebooks with various extensions, including improved load-high and extended

codepage In computing, a code page is a character encoding and as such it is a specific association of a set of printable characters and control characters with unique numbers. Typically each number represents the binary value in a single byte. (In some co ...

support
/ref> * Version 5.0a (Retail) – With this release, IBM and Microsoft versions diverge. * MS-DOS 5.50, Version 5.50 (Windows

NTVDM Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware. Overview Virtual DOS machines can operate ei ...

) – All Windows NT

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...

versions ship with files from DOS 5.0

MS-DOS 6.x

* Version 6.0 (Retail) – Online help through

QBASIC QBasic is an integrated development environment (IDE) and interpreter for a variety of dialects of BASIC which are based on QuickBASIC. Code entered into the IDE is compiled to an intermediate representation (IR), and this IR is immediately ex ...

. Disk compression, upper memory optimization and antivirus included. * Version 6.2 – SCANDISK as replacement for

CHKDSK In computing, CHKDSK (short for "check disk") is a system tool and command in DOS, Digital Research FlexOS, IBM/Toshiba 4690 OS, IBM OS/2, Microsoft Windows and related operating systems. It verifies the file system integrity of a volume and at ...

. Fix serious bugs in

DBLSPACE DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993 and ending in 2000 with the release of Windows Me. The purpose of DriveSpace is to increase the amount of data the ...

. * Version 6.21 (Retail) – Stacker-infringing DBLSPACE removed. * Version 6.22 (Retail) – New

DRVSPACE DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993 and ending in 2000 with the release of Windows Me. The purpose of DriveSpace is to increase the amount of data the ...

compression.

MS-DOS 7/8 (as part of Windows 9x)

* MS-DOS 7.0 was included in

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 manufacturin ...

's first retail release. It contains support for

VFAT 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 ...

long file names when run in a Windows Virtual 8086 box or with an LFN driver such as DOSLFN. JO.SYS is an alternative filename of the

IO.SYS is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS device drivers (hardware interfacing routines) and the DOS initialization program. Boot sequence In the PC bootup sequence, the first sector of the boot disk is ...

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 Ver or VER may refer to: * Voluntary Export Restraints, in international trade * VER, the IATA airport code for General Heriberto Jara International Airport * Volk's Electric Railway, Brighton, England * VerPublishing, of the German group VDM Publ ...

internal command reports the Windows version 4.00.950, applications through the

MS-DOS API The DOS API is an API which originated with 86-DOS and is used in MS-DOS/ PC DOS and other DOS-compatible operating systems. Most calls to the DOS API are invoked using software interrupt 21h ( INT 21h). By calling INT 21h with a subfunctio ...

would be reported a version number of 7.00. * MS-DOS 7.1 was included in

's OEM Service Release 2 through

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 ...

Second Edition. It added support for the

FAT32 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 ...

file system and

logical block addressing Logical block addressing (LBA) is a common scheme used for specifying the location of blocks of data stored on computer storage devices, generally secondary storage systems such as hard disk drives. LBA is a particularly simple linear addressi ...

(LBA), 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. * MS-DOS 8.0 was included in

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 Windo ...

, 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 Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...

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 DOS/V is a Japanese computing initiative starting in 1990 to allow DOS on IBM PC compatibles with VGA cards to handle double-byte (DBCS) Japanese text via software alone. It was initially developed from PC DOS by IBM for its PS/55 machines (a ...

), Korean, Arabic (ADOS 3.3/5.0), Hebrew (HDOS 3.3/5.0), Russian ( RDOS 4.01/

5.0 ''5.0'' is the sixth studio album by American rapper Nelly. It was released through Universal Motown Records (Universal Music Group) and Derrty (Universal Music Group) on November 12, 2010.

) as well as some other Eastern European versions of DOS.

Competition

On microcomputers based on the

and

8088 The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88) microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and ...

processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from

, whose

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 CP/M-86 was a version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The system commands are the same as in CP/M-80. Executable files used the relocatable .CMD file format. Digital Research als ...

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 program In computing, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instructions", as opposed to a data file ...

s for CP/M-86 and MS-DOS were not interchangeable with each other; many

applications Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

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 The domain name .com is a top-level domain (TLD) in the Domain Name System (DNS) of the Internet. Added at the beginning of 1985, its name is derived from the word ''commercial'', indicating its original intended purpose for domains registere ...

, 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 A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

.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 Exe or EXE may refer to: * .exe, a file extension * exe., abbreviation for executive Places * River Exe, in England * Exe Estuary, in England * Exe Island, in Exeter, England Transportation and vehicles * Exe (locomotive), a British locomotive ...

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 In economics, vendor lock-in, also known as proprietary lock-in or customer lock-in, makes a customer dependent on a vendor for products, unable to use another vendor without substantial switching costs. The use of open standards and alternative ...

. 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

operating system which ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called

. 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 The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-m ...

, early

Apple Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...

, the

Commodore 64 The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas). It has been listed in the Guinness ...

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 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 ...

. 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 In software design, the look and feel of a graphical user interface comprises aspects of its design, including elements such as colors, shapes, layout, and typefaces (the "look"), as well as the behavior of dynamic elements such as buttons, boxes ...

; 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 Norton Utilities is a utility software suite designed to help analyze, configure, optimize and maintain a computer. The latest version of the original series of Norton Utilities is Norton Utilities 16 for Windows XP/Vista/7/8 was released 26 Oc ...

, PC Tools (

Microsoft Anti-Virus Microsoft Anti-Virus (MSAV) is an antivirus program introduced by Microsoft for its MS-DOS operating system. The program first appeared in MS-DOS version 6.0 (1993) and last appeared in MS-DOS 6.22. The first version of the antivirus program was ...

QEMM Quarterdeck Expanded Memory Manager (QEMM) is a memory manager produced by Quarterdeck Office Systems in the late 1980s through the late 1990s. It was the most popular third-party memory manager for the MS-DOS and other DOS operating systems. ...

expanded memory manager,

Stacker A stacker is a large machine used in bulk material handling. Its function is to pile bulk material such as limestone, ores and cereals on to a stockpile. A reclaimer can be used to recover the material. Gold dredges in Alaska had a stacker ...

disk compression A disk compression software utility increases the amount of information that can be stored on a hard disk drive of given size. Unlike a file compression utility, which compresses only specified files—and which requires the user to designate ...

, and others. During the period when Digital Research was competing in the operating system market some computers, like

Amstrad PC1512 The Amstrad PC1512 was Amstrad's mostly IBM PC-compatible computer system, first manufactured in 1986. It was later succeeded by the PC1640. Features Whereas IBM's PC (and almost all PC compatibles) had a power supply in a corner of the main c ...

, 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 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 e ...

, 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

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 Fear, uncertainty and doubt (often shortened to FUD) is a propaganda tactic used in sales, marketing, public relations, politics, polling and cults. FUD is generally a strategy to influence perception by disseminating negative and dubious or ...

) 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 Brad Silverberg is an American computer scientist and businessman, most noted for his work at Microsoft in 1990–1999 as Senior VP and product manager for MS-DOS, Windows, Internet Explorer, and Office. He was named ''PC Magazine''s Person of the ...

, 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). (xviii+856+vi pages, 3.5"-floppy) Errata

/ref>

The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when

Windows 3.0 Windows 3.0 is the third major release of Microsoft Windows, launched in 1990. It features a new graphical user interface (GUI) where applications are represented as clickable icons, as opposed to the list of file names seen in its predecesso ...

became a marketplace success. Much of Microsoft's further contributions to OS/2 also went into creating a third

GUI The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

replacement for DOS,

Windows NT Windows NT is a proprietary graphical 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 sc ...

. 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

DR DOS 6.0 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-D ...

, which bundled SuperStor disk compression, Microsoft opened negotiations with

Stac Electronics Stac Electronics, originally incorporated as State of the Art Consulting and later shortened to Stac, Inc., was a technology company founded in 1983. It is known primarily for its Lempel–Ziv–Stac lossless compression algorithm and Stacker dis ...

, vendor of the most popular DOS disk compression tool, Stacker. In the

due diligence Due diligence is the investigation or exercise of care that a reasonable business or person is normally expected to take before entering into an agreement or contract with another party or an act with a certain standard of care. It can be a l ...

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 The Federal Trade Commission (FTC) is an independent agency of the United States government whose principal mission is the enforcement of civil (non-criminal) antitrust law and the promotion of consumer protection. The FTC shares jurisdiction ov ...

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 A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

, sued Microsoft for damages in the ''

Caldera v. Microsoft Microsoft has been involved in numerous high-profile legal matters that involved litigation over the history of the company, including cases against the United States, the European Union, and competitors. Governmental In its 2008 annual report, Mi ...

'' lawsuit. It was believed that the settlement ran in the order of , but was revealed in November 2009 with the release of the Settlement Agreement to be .

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 The Program Segment Prefix (PSP) is a data structure used in DOS systems to store the state of a program. It resembles the Zero Page in the CP/M operating system. The PSP has the following structure: The PSP is most often used to get the comm ...

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 Microsoft QuickC is a discontinued commercial integrated development environment (IDE) product engineered by Microsoft for the C programming language, superseded by Visual C++ Standard Edition. Its main competitor was Borland Turbo C. QuickC is ...

v2.5, Programmer's Workbench and Microsoft C v6.0. * The

AARD code The AARD code was a segment of code in a beta release of Microsoft Windows 3.1 that would determine whether Windows was running on MS-DOS or PC DOS, rather than a competing workalike such as DR-DOS, and would result in a cryptic error messag ...

, 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

have had an MS-DOS or MS-DOS-like

command-line interface A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...

called

MS-DOS Prompt COMMAND.COM is the default command-line interpreter for MS-DOS, Windows 95, Windows 98 and Windows Me. In the case of DOS, it is the default user interface as well. It has an additional role as the usual first program run after boot (init proc ...

which redirected input to MS-DOS and output from MS-DOS to the MS-DOS Prompt, or, in later versions,

Command Prompt Command Prompt, also known as cmd.exe or cmd, is the default command-line interpreter for the OS/2, eComStation, ArcaOS, Microsoft Windows (Windows NT family and Windows CE family), and ReactOS operating systems. On Windows CE .NET 4.2, Wind ...

. This could run many DOS and variously Win32, OS/2 1.x and

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 interf ...

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 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...

versions of Windows (up to 3.11) ran as a Graphical User Interface (GUI) on top of MS-DOS. With

, 98, and Me, the role of MS-DOS was reduced to a boot loader according to Microsoft, 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. However, Windows 9x still runs under DOS, and it has been stated that there is almost no difference in the relationship between Windows 9x and its included MS-DOS 7.x and Windows 3.x and MS-DOS 6.x. 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

(NT Virtual DOS Machine). This is a modified

SoftPC SoftPC is a software emulator of x86 hardware. It was developed by Rod MacGregor, Henry Nash & Phil Bousfield, following the founding of Insignia Solutions in 1986 By MacGregor, with "about a dozen people who had left the CAD/CAM workstation speci ...

(a former product similar to

VirtualPC Windows Virtual PC (successor to Microsoft Virtual PC 2007, Microsoft Virtual PC 2004, and Connectix Virtual PC) is a Hardware virtualization, virtualization program for Microsoft Windows. In July 2006, Microsoft released the Windows version f ...

), 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 In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems. Debugging tactics can involve int ...

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 initialization determined by _DEFAULT.PIF, optionally permitting the use of

Win32 console Windows Console is the infrastructure for console applications in Microsoft Windows. An instance of a Windows Console has a screen buffer and an input buffer. It allows console apps to run inside a window or in hardware text mode (so as to oc ...

applications and internal commands with an NTCMDPROMPT directive.

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 Itanium ( ) is a discontinued family of 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Launched in June 2001, Intel marketed the processors for enterprise servers and high-performance computin ...

(no longer sold by Microsoft) and

x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mod ...

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 In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardw ...

emulators such as Microsoft's own

Virtual PC Windows Virtual PC (successor to Microsoft Virtual PC 2007, Microsoft Virtual PC 2004, and Connectix Virtual PC) is a virtualization program for Microsoft Windows. In July 2006, Microsoft released the Windows version free of charge. In August ...

, as well as

VMware VMware, Inc. is an American cloud computing and virtualization technology company with headquarters in Palo Alto, California. VMware was the first commercially successful company to virtualize the x86 architecture. VMware's desktop software ru ...

DOSBox DOSBox is a free and open-source emulator which runs software for MS-DOS compatible disk operating systems—primarily video games. It was first released in 2002, when DOS technology was becoming obsolete. Its adoption for running DOS games i ...

etc., unofficial compatibility layers such as NTVDMx64, OTVDM (WineVDM), Win3mu and others.

End-of-life

The introduction of

in 1990, with an easy-to-use

, marked the beginning of the end for the command-line driven MS-DOS. With the release of

(and continuing in the

Windows 9x Windows 9x is a generic term referring to a series of Microsoft Windows computer operating systems produced from 1995 to 2000, which were based on the Windows 95 kernel and its underlying foundation of MS-DOS, both of which were updated in subs ...

product line through to

), an integrated version of MS-DOS was used for

bootstrapping In general, bootstrapping usually refers to a self-starting process that is supposed to continue or grow without external input. Etymology Tall boots may have a tab, loop or handle at the top known as a bootstrap, allowing one to use fingers ...

, 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 July 11, 2006, thus ending support and updates of MS-DOS from Microsoft. In contrast to the Windows 9x series, the

-derived 32-bit operating systems (

2000 File:2000 Events Collage.png, From left, clockwise: Protests against Bush v. Gore after the 2000 United States presidential election; Heads of state meet for the Millennium Summit; The International Space Station in its infant form as seen from ...

, 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

(NT Virtual DOS Machine) to run DOS applications and provide DOS-like command prompt windows.

64-bit In computer architecture, 64-bit Integer (computer science), integers, memory addresses, or other Data (computing), data units are those that are 64 bits wide. Also, 64-bit central processing unit, CPUs and arithmetic logic unit, ALUs are those ...

versions of Windows NT prior to

Windows 11 Windows 11 is the latest major release of Microsoft's Windows NT operating system, released in October 2021. It is a free upgrade to its predecessor, Windows 10 (2015), and is available for any Windows 10 devices that meet the new Windows 11 ...

do not provide DOS emulation and cannot run DOS applications natively.

contains a copy of the

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 AUTOEXEC.BAT is a system file that was originally on DOS-type operating systems. It is a plain-text batch file in the root directory of the boot device. The name of the file is an abbreviation of "automatic execution", which describes its funct ...

and

CONFIG.SYS CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing ...

) 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 Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...

COMMAND.COM 





COMMAND.COM is the default command-line interpreter for MS-DOS, Windows 95, Windows 98 and Windows Me. In the case of DOS, it is the default user interface as well. It has an additional role as the usual first program run after boot (init proc ...

. Windows 7, 8, and 8.1 can also create a MS-DOS startup disk. Starting with

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...

, the ability to create a DOS startup disk has been removed and so either a

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 FreeDOS (formerly Free-DOS and PD-DOS) is a free software operating system for IBM PC compatible computers. It intends to provide a complete MS-DOS-compatible environment for running Legacy system, legacy software and supporting embedded system ...

or even copying the required files and boot sector themselves. Starting with Windows 11, the operating system removed NTVDM entirely from the system as it no longer offers 32-bit versions of the operating system (being solely offered in 64-bit versions only), thus removing any traces of MS-DOS from Windows and Microsoft which in turn ended the 40-year legacy of MS-DOS. MS-DOS 6.22 was the last standalone version produced by Microsoft for

Intel 8088 The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88) microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers an ...

, and

Intel 80286 The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non-multiplexed address and data buses and also the fi ...

processors, which remain available for download via their

MSDN Microsoft Developer Network (MSDN) was the division of Microsoft responsible for managing the firm's relationship with developers and testers, such as hardware developers interested in the operating system (OS), and software developers developing ...

, 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

. In 2018, Microsoft released th
source code for MS-DOS 1.25 and 2.0
on

GitHub GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, continuous ...

. 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 request In software development, distributed version control (also known as distributed revision control) is a form of version control in which the complete codebase, including its full history, is mirrored on every developer's computer. Compared to centra ...

s to the code; only pull requests for modified and translated documentation will be accepted. Users, however, are allowed and fully encouraged to

fork In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods ei ...

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

s (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 Windows 1.0 is the first major release of Microsoft Windows, a family of graphical operating systems for personal computers developed by Microsoft. It was first released to manufacturing in the United States on November 20, 1985, while the Eur ...

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 A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, a ...

. After version 3.0, Windows gained market acceptance.

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.

runs independently of DOS but includes

, a component for simulating a DOS environment for legacy applications.

Related systems

MS-DOS compatible systems include: *

Novell 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-D ...

OpenDOS 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-D ...

ROM-DOS Datalight was a privately held software company specializing in power failsafe and high performance software for preserving data integrity in embedded systems. The company was founded in 1983 by Roy Sherrill, and is headquartered in Bothell, Washi ...

Microsoft manufactured

for IBM. It and MS-DOS were identical products that eventually diverged starting with MS-DOS version 6.0.

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.

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
{{Authority control 1981 software Assembly language software Discontinued Microsoft operating systems Disk operating systems DOS variants Floppy disk-based operating systems Formerly proprietary software Free software operating systems Microcomputer software Microsoft free software Proprietary operating systems Software using the MIT license

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

MS-DOS 6.x

MS-DOS 7/8 (as part of Windows 9x)

Localized versions

Competition

Legal issues

Use of undocumented APIs

Windows command-line interface

Earlier versions of Windows

Windows NT

End-of-life

Legacy compatibility

Related systems

See also

Notes

References

External links