MS-DOS

MS-DOS (play /ˌɛmɛsˈdɒs/ EM-es-DOSS; abbreviate for Microsoft Disk Operating System) is an operating arrangement for x86-based claimed computers. It was the best frequently acclimated affiliate of the DOS ancestors of operating systems, and was the capital operating arrangement for IBM PC accordant claimed computers during the 1980s to the mid 1990s, until it was gradually abolished by operating systems alms a graphical user interface (GUI), in accurate by assorted ancestors of the Microsoft Windows operating system.

MS-DOS grew from a 1981 appeal by IBM for an operating arrangement for its IBM PC ambit of claimed computers. Microsoft bound bought the rights to QDOS (Quick and Dirty Operating System), additionally accepted as 86-DOS,2 from Seattle Computer Products, and began assignment on modifying it to accommodated IBM's specification. The aboriginal edition, MS-DOS 1.0, was launched in 1982.3 The adaptation alien with IBM's PCs was alleged PC DOS. Although MS-DOS and PC DOS were initially developed in alongside by Microsoft and IBM, the two articles eventually went their abstracted ways.

During its life, several aggressive articles were appear for the x86 platform,4 and MS-DOS itself would go through eight versions, until development accomplished in 2000. Ultimately it was the key artefact in Microsoft's advance from a programming languages aggregation to a assortedcomputer application development firm, accouterment the aggregation with capital acquirement and business resources. It was additionally the basal basal operating arrangement on which aboriginal versions of Windows ran as a GUI.

History

MS-DOS was a renamed anatomy of 86-DOS – artlessly accepted as the Quick-and-Dirty Operating Arrangement or Q-DOS3 – endemic by Seattle Computer Products, accounting by Tim Paterson.3 Microsoft bare an operating arrangement for the then-new Intel 8086 but it had none available, so it bought 86-DOS for $75,000 and accountant it as its own again appear a adaptation of it as MS-DOS 1.0.3 Development started in 1981, and MS-DOS 1.0 was appear with the IBM PC in 1982.3 (86-DOS, in turn, was a carbon of Digital Research's CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M, an bigger deejay area buffering argumentation and the addition of FAT12 instead of the CP/M filesystem. This became accessible because of the added availability of RAM compared to what was about accessible back CP/M was advised originally.)

Originally MS-DOS was advised to be an operating arrangement that could run on any 8086-family computer. Each computer would accept its own audible accouterments and its own adaptation of MS-DOS, agnate to the bearings that existed for CP/M, and with MS-DOS battling the aforementioned band-aid as CP/M to acclimate for altered accouterments platforms. To this end, MS-DOS was advised with a modular anatomy with centralized accessory drivers, minimally for primary deejay drives and the console, chip with the atom and loaded by the cossack loader, and installable accessory drivers for added accessories loaded and chip at cossack time. The OEM would use a development kit provided by Microsoft to body a adaptation of MS-DOS with their basal I/O drivers and a accepted Microsoft kernel, which they would about accumulation on deejay to end users forth with the hardware. Thus, there were abounding altered versions of "MS-DOS" for altered hardware, and there is a aloft acumen amid an IBM-compatible (or ISA) apparatus and an MS-DOS compatible machine. Some machines, like the Tandy 2000, were MS-DOS accordant but not IBM-compatible, so they could alone runcomputer appliance accounting alone for MS-DOS after assurance on the borderline accouterments of the IBM PC architecture.

This architectonics would accept formed able-bodied for compatibility, if appliance programs had alone acclimated MS-DOS casework to accomplish accessory I/O, and absolutely the aforementioned architectonics aesthetics is embodied in Windows NT (see Accouterments Abstraction Layer). However, in MS-DOS's aboriginal days, the greater acceleration accessible by programs through absolute ascendancy of accouterments was of accurate importance, abnormally for games, which generally pushed the banned of their abreast hardware. Actual anon an IBM-compatible architectonics became the goal, and afore continued all 8086-family computers carefully emulated IBM's hardware, and alone a distinct adaptation of MS-DOS for a anchored accouterments belvedere was bare for the market. This adaptation is the adaptation of MS-DOS that is discussed here, as the dozens of added OEM versions of "MS-DOS" were alone accordant to the systems they were advised for, and in any case were actual agnate in action and adequacy to the same-numbered accepted adaptation for the IBM PC, with a few notable exceptions.

While MS-DOS appeared on PC clones, accurate IBM computers acclimated PC DOS, a rebranded anatomy of MS-DOS. Ironically, the assurance on IBM-compatible accouterments acquired aloft problems for the computer industry back the aboriginal architectonics had to be changed. For example, the aboriginal architectonics could abutment no added than 640 kilobytes of anamnesis (the 640 KB barrier), because IBM's accouterments architectonics aloof the abode amplitude aloft this absolute for borderline accessories and ROM. Manufacturers had to advance complicated schemes (EMS and XMS, and added accessory proprietary ones) to admission added memory. This limitation would not accept been a botheration if the aboriginal abstraction of interfacing with accouterments through MS-DOS had endured. (However, MS-DOS was additionally a real-mode operating system, and the Intel x86 architectonics alone supports up to 1 MB of anamnesis abode amplitude in Real Mode, alike on Pentium 4 and after x86 CPUs, so for simple admission to megabytes of memory, MS-DOS would accept had to be rewritten to run in 80286 or 80386 Protected Mode.) Also, Microsoft originally declared MS-DOS as "an operating arrangement for Intel 8086-based microcomputers", and the 8086 CPU (and its accessory the 8088) itself has alone 1 MiB of absolute anamnesis abode space.

Competition

On microcomputers based on the Intel 8086 and 8088 processors, including the IBM PC and clones, the antecedent antagonism to the PC DOS/MS-DOS band came from Digital Research, whose CP/M operating arrangement had aggressive MS-DOS. In fact, there charcoal altercation as to whether Q-DOS was added or beneath plagiarised from aboriginal versions of CP/M code. Digital Research arise CP/M-86 a few months afterwards MS-DOS, and it was offered as an another to MS-DOS and Microsoft's licensing requirements, but at a college price. Executable programs for CP/M-86 and MS-DOS were not changeable with anniversary other; abundant applicationscomputer application was awash in both MS-DOS and CP/M-86 versions until MS-DOS became best (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS originally accurate the simple .COM, which was modelled afterwards a agnate but bifold adverse architectonics accepted from CP/M-80. CP/M-86 instead accurate a relocatable architectonics application the book addendum .CMD to abstain name conflicts with CP/M-80 and MS-DOS .COM files. MS-DOS adaptation 2.0 added a added avant-garde relocatable .EXE executable book format.

Most of the machines in the aboriginal canicule of MS-DOS had differing arrangement architectures and there was a assertive amount of incompatibility, and afterwards bell-ringer lock-in. Users who began application MS-DOS with their machines were accountable to abide application the adaptation customized for their hardware, or face aggravating to get all of their proprietary accouterments andcomputer application to assignment with the fresh system.

In the business apple the 808x-based machines that MS-DOS was angry to faced antagonism from the Unix operating arrangement which ran on abounding altered accouterments architectures. Microsoft itself awash a adaptation of Unix for the PC alleged Xenix.

In the arising apple of home users, a array of added computers based on assorted added processors were in austere antagonism with the IBM PC: the Apple II, aboriginal Apple Macintosh, the Commodore 64 and others did not use the 808x processor; abounding 808x machines of altered architectures acclimated custom versions of MS-DOS. At aboriginal all these machines were in competition. In time the IBM PC accouterments agreement became ascendant in the 808x bazaar ascomputer application accounting to acquaint anon with the PC accouterments afterwards application accepted operating arrangement calls ran abundant faster, but on accurate PC-compatibles only. Non-PC-compatible 808x machines were too baby a bazaar to accept fastcomputer application accounting for them alone, and the bazaar remained accessible abandoned for IBM PCs and machines that anxiously apish their architecture, all active either a distinct adaptation of MS-DOS accordant abandoned with PCs, or the agnate IBM PC DOS. Best clones amount abundant beneath than IBM-branded machines of agnate performance, and became broadly acclimated by home users, while IBM PCs had a ample allotment of the business computer market.

Microsoft and IBM calm began what was advised as the follow-on to MS-DOS/PC DOS, alleged OS/2. Back OS/2 was arise in 1987, Microsoft began an announcement attack announcement that "DOS is Dead" and advertence that adaptation 4 was the aftermost abounding release. OS/2 was advised for able multi-tasking — an IBM aspect acquired from abysmal acquaintance with mainframe operating systems — and offered a cardinal of avant-garde appearance that had been advised calm with agnate attending and feel; it was apparent as the accepted beneficiary to the "kludgy" DOS platform.

MS-DOS had developed in spurts, with abounding cogent appearance actuality taken or bifold from Microsoft's added articles and operating systems. MS-DOS additionally grew by incorporating, by absolute licensing or affection duplicating, the functionality of accoutrement and utilities developed by absolute companies, such as Norton Utilities, PC Accoutrement (Microsoft Anti-Virus), QEMM broadcast anamnesis manager, Stacker deejay compression, and others.

During the aeon back Digital Research was aggressive in the operating arrangement bazaar some computers, like Amstrad PC1512, were awash with billowing disks for two operating systems (only one of which could be acclimated at a time), MS-DOS and CP/M-86 or a acquired of it. Digital Research produced DOS Plus, which was accordant with MS-DOS 2.11, accurate CP/M-86 programs, had added appearance including multi-tasking, and could apprehend and address disks in CP/M and MS-DOS format.

While OS/2 was beneath abiding development, Digital Research arise the MS-DOS accordant DR-DOS 5, which included appearance abandoned accessible as third-party add-ons for MS-DOS (and still maintained ample centralized CP/M-86 compatibility). Unwilling to lose any allocation of the market, Microsoft responded by announcement the "pending" absolution of MS-DOS 5.0 in May 1990. This finer dead best DR-DOS sales until the absolute absolution of MS-DOS 5.0 in June 1991. Digital Research brought out DR-DOS 6, which awash able-bodied until the "pre-announcement" of MS-DOS 6.0 afresh aside the sales of DR-DOS.

Microsoft had been accused of anxiously orchestrating leaks about approaching versions of MS-DOS in an attack to actualize what in the industry is alleged FUD (fear, uncertainty, and doubt) apropos DR-DOS. For example, in October 1990, anon afterwards the absolution of DR-DOS 5.0, and continued afore the closing June 1991 absolution of MS-DOS 5.0, belief on affection enhancements in MS-DOS started to arise in InfoWorld and PC Week. Brad Silverberg, Vice President of Systems Computer application at Microsoft and General Administrator of its Windows and MS-DOS Business Unit, wrote a bull letter to PC Week (November 5, 1990), abstinent that Microsoft was affianced in FUD approach ("to serve our barter better, we absitively to be added accessible about adaptation 5.0") and abstinent that Microsoft affected appearance from DR-DOS:

"The affection enhancements of MS-DOS adaptation 5.0 were absitively and development was amorphous continued afore we heard about DR-DOS 5.0. There will be some agnate features. With 50 actor MS-DOS users, it shouldn't be hasty that DRI has heard some of the aforementioned requests from barter that we have." – (Schulman et al. 1994).10

The alliance amid Microsoft and IBM to advance OS/2 began to abatement afar in 1990 back Windows 3.0 became a exchange success. Abundant of Microsoft's added contributions to OS/2 additionally went in to creating a third GUI backup for DOS, Windows NT.

IBM, which had already been developing the abutting adaptation of OS/2, agitated on development of the belvedere afterwards Microsoft and awash it as the another to DOS and Windows.

Legal issues

As a acknowledgment to Digital Research's DR DOS 6.0, which arranged SuperStor deejay compression, Microsoft opened negotiations with Stac Electronics, bell-ringer of the best accepted DOS deejay compression tool, Stacker. In the due activity process, Stac engineers had apparent Microsoft allotment of the Stacker antecedent code. Stac was afraid to accommodated Microsoft's acceding for licensing Stacker and withdrew from the negotiations. Microsoft chose to authorization Vertisoft's DoubleDisk, application it as the amount for its DoubleSpace deejay compression.11

MS-DOS 6.0 and 6.20 were appear in 1993, both including the Microsoft DoubleSpace deejay compression account program. Stac auspiciously sued Microsoft for apparent contravention apropos the compression algorithm acclimated in DoubleSpace. This resulted in the 1994 absolution of MS-DOS 6.21, which had disk-compression removed. Shortly afterwards came adaptation 6.22, with a fresh adaptation of the deejay compression system, DriveSpace, which had a altered compression algorithm to abstain the anarchic code.

Prior to 1995, Microsoft accountant MS-DOS (and Windows) to computer manufacturers beneath three types of agreement: per-processor (a fee for anniversary adjustment the aggregation sold), per-system (a fee for anniversary adjustment of a accurate model), or per-copy (a fee for anniversary archetype of MS-DOS installed). The better manufacturers acclimated the per-processor arrangement, which had the everyman fee. This adjustment fabricated it big-ticket for the ample manufacturers to drift to any added operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, consistent in a 1994 adjustment acceding attached Microsoft to per-copy licensing. Digital Research did not accretion by this settlement, and years after its almsman in interest, Caldera, sued Microsoft for damages. It was believed that the adjustment ran in the adjustment of $150m, but was appear in November 2009 with the absolution of the Adjustment Acceding to be $280m.citation needed

Use of undocumented APIs

Microsoft additionally acclimated a array of approach in MS-DOS and several of their applications and development accoutrement that, while operating altogether back active on 18-carat MS-DOS (and PC DOS), would breach back run on addition vendor's accomplishing of DOS. Notable examples of this convenance included:

Microsoft's QuickPascal appear in aboriginal 1989 was the aboriginal MS artefact that arrested for MS-DOS by modifying the program's Program Articulation Prefix application undocumented DOS functions, and again arrested whether or not the associated amount afflicted in a anchored position aural the DOS abstracts articulation (also undocumented). This analysis additionally fabricated it into after MS products, including Microsoft QuickC v2.5, Programmer's Workbench and Microsoft C v6.0.10

The (once infamous) AARD code, a block of cipher in the Windows 3.1 beta installer. It was XOR encrypted, self-modifying, and advisedly obfuscated, application assorted undocumented DOS structures and functions to actuate whether or not Windows absolutely was active on MS-DOS.10

Note that the Windows 3.0 beta cipher alone gave a admonishing that Windows would not accomplish appropriately on a "foreign" OS. It did in actuality run aloof accomplished on DR-DOS 6.0.

Interrupt routines alleged by Windows to acquaint MS-DOS that Windows is starting/exiting, advice that MS-DOS retained in an IN_WINDOWS flag, in animosity of the actuality that MS-DOS and Windows were declared to be two abstracted products.10

End of MS-DOS

Today, MS-DOS is not often acclimated for desktop computing. Since the absolution of Windows 95, it was chip as a abounding artefact acclimated for bootstrapping and troubleshooting, and no best appear as a standalone product.

Windows XP contains a archetype of the Windows Me cossack disk, bare bottomward to bootstrap only. This is attainable alone by formatting a billowing as an "MS-DOS startup disk". Files like the disciplinarian for the CD-ROM abutment were deleted from the Windows ME bootdisk and the startup files (AUTOEXEC.BAT and CONFIG.SYS) no best had a content. This adapted deejay was the abject for creating the MS-DOS angel for Windows XP. Some of the deleted files can be recovered with an undelete tool.12 With Windows Vista the files on the startup deejay are anachronous 18 April 2005 but are contrarily unchanged, including the cord "MS-DOS Version 8 © Copyright 1981-1999 Microsoft Corp" central COMMAND.COM.

However the alone versions of DOS currently accustomed as stand-alone OSs, and accurate as such by the Microsoft Corporation are DOS 6.0 and 6.22, both of which abide accessible for download via their MSDN, aggregate license, and OEM authorization accomplice websites, for barter with accurate login credentials.

MS-DOS is still acclimated in anchored x86 systems due to its simple architecture, and basal anamnesis and processor requirements. The command band analyst of NT-based versions of Windows, cmd.exe, maintains best of the aforementioned commands and some affinity with DOS accumulation files.

Windows command-line interface

All versions of Microsoft Windows accept had an MS-DOS like command-line interface (CLI). This could run abounding DOS and abnormally Win32, OS/2 1.x and Posix command band utilities in the aforementioned command-line session, acceptance brim amid commands. The user interface, and the figure up to Windows 2000, followed the built-in MS-DOS interface.

Consumer Windows (up to 3.11, Win9x, WinME) ran as a Graphical User Interface (GUI) active on top of MS-DOS. With Windows 95, 98, and ME the MS-DOS allotment was integrated, alleviative both operating systems as a complete package. The command band accessed the DOS command band (usually command.com), through a Windows bore (winoldap.mod).

A fresh band of Windows, (Windows NT), cossack through a atom whose sole purpose is to amount Windows: there is no character-mode cossack agnate to Consumer Windows, OS/2 or UNIX). The animate runs as a Win32 session, with the absence processor cmd.exe actuality a feature-reduced adaptation of OS/2's version. The command affair permits active of assorted accurate command band utilities from Win32, MS-DOS, OS/2 1.x and POSIX.

The 32-bit Windows can run MS-DOS programs through the use of the NTVDM (NT Virtual DOS Machine). This launches a barbate adaptation of MS-DOS 5.0. Launching any DOS appliance such as the DOS command processor command.com creates a 16-bit sub-system accouterment best of the college akin DOS APIs for DOS programs to run and alike acquaint with anniversary other.

The 32-bit CLI is usually referred to as the MS-DOS prompt. Although the bifold interface is no best that begin in PC DOS etc., it is an 'interface', and not an API. The commands typed here, the batches etc., all resemble those of MS-DOS/PC DOS in abundant the aforementioned way that the Linux/UNIX commands resemble anniversary added after basal bifold compatibility.

All versions of Windows for x86-64 and Itanium architectures no best accommodate the NTVDM and can accordingly no best natively run MS-DOS or 16-bit Windows applications. There are alternatives in the anatomy of Virtual apparatus emulators such as Microsoft's own Virtual PC, as able-bodied as VMware, DOSBox, and others.