Legacy Family Tree v2.0 September 99 serial key or number

MS-DOS (/ˌɛmˌɛsˈdɒs/em-es-DOSS; acronym for Microsoft Disk Operating System) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and some 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 personal computers during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system.

IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax, and capabilities.

During its lifetime, several competing products were released for the x86 platform,^[5] and MS-DOS went through eight versions, until development ceased in 2000.^[6] Initially, MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in ever greater sizes and formats, along with added feature support for newer processors and rapidly evolving computer architectures. Ultimately, it was the key product in Microsoft's development from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI. It is a flexible operating system, and consumes negligible installation space.

History[edit]

MS-DOS was a renamed form of 86-DOS^[7] – owned by Seattle Computer Products, written by Tim Paterson. Development of 86-DOS took only six weeks, as it was basically a clone of Digital Research's CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M: an improved disk sector buffering logic, and the introduction of FAT12 instead of the CP/M filesystem. This first version was shipped in August 1980.^[3] Microsoft, which needed an operating system for the IBM Personal Computer,^[8][9] hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for US$75,000 in July of the same year. Microsoft kept the version number, but renamed it MS-DOS. They also licensed MS-DOS 1.10/1.14 to IBM, which, in August 1981, offered it as PC DOS 1.0 as one of three operating systems^[10] for the IBM 5150, or the IBM PC.^[3]

Within a year, Microsoft licensed MS-DOS to over 70 other companies.^[11] It was designed to be an OS that could run on any 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, and with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers (the DOS BIOS), minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, and installable device drivers for other devices loaded and integrated at boot time. The OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and a standard Microsoft kernel, which they would typically supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, and there is a major distinction between an IBM-compatible (or ISA) machine and an MS-DOS [compatible] machine. Some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could run software written exclusively for MS-DOS without dependence on the peripheral hardware of the IBM PC architecture.

This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O, and indeed the same design philosophy is embodied in Windows NT (see Hardware Abstraction Layer). However, in MS-DOS's early days, the greater speed attainable by programs through direct control of hardware was of particular importance, especially for games, which often pushed the limits of their contemporary hardware. Very soon an IBM-compatible architecture became the goal, and before long all 8086-family computers closely emulated IBM's hardware, and only a single version of MS-DOS for a fixed hardware platform was needed for the market. This version is the version of MS-DOS that is discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to the systems they were designed for, and in any case were very similar in function and capability to some standard version for the IBM PC—often the same-numbered version, but not always, since some OEMs used their own proprietary version numbering schemes (e.g. labeling later releases of MS-DOS 1.x as 2.0 or vice versa)—with a few notable exceptions.

Microsoft omitted multi-user support from MS-DOS because Microsoft's Unix-based operating system, Xenix, was fully multi-user.^[12] The company planned, over time, to improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the Motorola 68000, Zilog Z8000, and the LSI-11; they would be upwardly compatible with Xenix, which Byte in 1983 described as "the multi-user MS-DOS of the future".^[13][14] Microsoft advertised MS-DOS and Xenix together, listing the shared features of its "single-user OS" and "the multi-user, multi-tasking, UNIX-derived operating system", and promising easy porting between them.^[15] After the breakup of the Bell System, however, AT&T Computer Systems started selling UNIX System V. Believing that it could not compete with AT&T in the Unix market, Microsoft abandoned Xenix, and in 1987 transferred ownership of Xenix to the Santa Cruz Operation (SCO).

On March 25, 2014, Microsoft made the code to SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11 available to the public under the Microsoft Research License Agreement, which makes the code source-available, but not open source as defined by Open Source Initiative or Free Software Foundation standards.^{[16][17][18][19]} Microsoft would later re-license the code under the MIT License on September 28, 2018, making these versions free software.^[2]

As an April Fool's Day joke in 2015, Microsoft Mobile launched a Windows Phone application called MS-DOS Mobile which was presented as a new mobile operating system and worked similar to MS-DOS.^[20]

Versions[edit]

Microsoft licensed or released versions of MS-DOS under different names like Lifeboat Associates "Software Bus 86"^[21][22] a.k.a. SB-DOS,^[5]COMPAQ-DOS,^[21][22]NCR-DOS or Z-DOS^[21][5] before it eventually enforced the MS-DOS name for all versions but the IBM one, which was originally called "IBM Personal Computer DOS", later shortened to IBM PC DOS. (Competitors released compatible DOS systems such as DR DOS and PTS-DOS that could also run DOS applications.)

In the former Eastern bloc, MS-DOS derivatives named DCP (Disk Control Program [de]) 3.20 and 3.30 existed in the late 1980s. They were produced by the East German electronics manufacturer VEB Robotron.^[23]

The following versions of MS-DOS were released to the public:^[24][25]

MS-DOS 1.x[edit]

MS-DOS Version 1.12 for Compaq Personal Computer

• Version 1.24 (OEM) – basis for IBM's Personal Computer DOS 1.1
• Version 1.25 (OEM) – basis for non-IBM OEM versions of MS-DOS, including SCP MS-DOS 1.25

• Compaq-DOS 1.12, a Compaq OEM version of MS-DOS 1.25; Release date: November, 1983^[26]
• TI BOOT V. 1.13, a Texas Instruments OEM version of MS-DOS; Release date: August, 1983^[27]
• Zenith Z-DOS 1.19, a Zenith OEM version of MS-DOS 1.25^[28]
• Zenith Z-DOS/MS-DOS release 1.01, version 1.25, a Zenith OEM version of MS-DOS; Release date: May, 1983^[29]

MS-DOS 2.x[edit]

Support for IBM's XT 10 MB hard disk drives, support up to 16 MB or 32 MB FAT12 formatted hard disk drives depending on the formatting tool shipped by OEMs,^[30] user installable device drivers, tree-structure filing system,^[31] Unix-like^[32] inheritable redirectable file handles,^[33][34] non-multitasking child processes^[35] an improved Terminate and Stay Resident (TSR) API,^[36] environment variables, device driver support, FOR and GOTO loops in batch files, ANSI.SYS.^[37]

• Version 2.0 (OEM), First version to support 5.25-inch, 180 KB and 360 KB floppy disks;^[38][39] Release date: October, 1983^[40]
• Version 2.02 (OEM, Compaq); Release date: November, 1983^[41]
• Version 2.05 (OEM, international support);^[21] Release date: October, 1983^[42]
• Version 2.1 (OEM, IBM only)^[21]
• Version 2.11 (OEM)^[21]
  • Altos MS-DOS 2.11, an Altos OEM version of MS-DOS 2.11 for the ACT-86C
  • ITT Corporation ITT-DOS 2.11 Version 2 (MS-DOS 2.11 for the ITT XTRA Personal Computer); Release date: July, 1985^[43]
  • Toshiba MS-DOS 2.11 in ROM drive for the model T1000 laptop
  • TeleVideo PC DOS 2.11, a TeleVideo OEM version of MS-DOS 2.11
• Version 2.13 (OEM, Zenith); Release date: July, 1984^[44]
• Version 2.2 (OEM, with Hangeul support)^[21]
• Version 2.25 (OEM, with Hangeul and Kanji support)^[21]

MS-DOS 3.x[edit]

• Version 3.0 (OEM) – First version to support 5.25-inch, 1.2 MB floppy drives and diskettes, FAT16 partitions up to 32 MB;^[45][46] Release date: April, 1985^[47]
• Version 3.1 (OEM) – Support for Microsoft Networks through an IFS layer,^[45] remote file and printer API^[48][49]
• Version 3.2 (OEM) – First version to support 3.5-inch, 720 kB floppy drives and diskettes and XCOPY.^[38]
• Version 3.10 (OEM, Multitech); Release date: May, 1986^[50]
• Version 3.20 – First retail release (non-OEM); Release date: July, 1986^[51]
• Version 3.21 (OEM / non-OEM); Release date: May, 1987^[52]
• Version 3.22 (OEM) – (HP 95LX)
• Version 3.25 (OEM)
• Version 3.3 (OEM) – First version to support 3.5-inch, 1.44 MB floppy drives and diskettes, extended and logical partitions, directory tree copying with XCOPY, improved support for internationalization (COUNTRY.SYS),^[53] networked file flush operations^[54]
• Version 3.3a (OEM)
• Version 3.30; Release date: February, 1988^[55]
• Version 3.30A (OEM, DTK); Release date: July, 1987^[56]
• Version 3.30T (OEM, Tandy); Release date: July, 1990^[57]
• Version 3.31 (Compaq OEM only)^{[nb 1]} – supports FAT16B with partitions larger than 32 MiB;^{[nb 2]} Release date: November, 1989^[58]

MS-DOS 4.0 / MS-DOS 4.x[edit]

• MS-DOS 4.0 (multitasking) and MS-DOS 4.1 – A separate branch of development with additional multitasking features, released between 3.2 and 3.3, and later abandoned. It is unrelated to any later versions, including versions 4.00 and 4.01 listed below
• MS-DOS 4.x (IBM-developed) – includes a graphical/mouse interface. It had many bugs and compatibility issues.^[59]
  • 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,^[60]FASTOPEN/FASTSEEK, DOSSHELL, could use EMS for the disk buffers and provided EMS drivers and emulation for 386 compatible processors;^[61] Release date: October, 1988^[62]
  • Version 4.01 (OEM) – Microsoft rewritten Version 4.00 released under MS-DOS label but not IBM PC DOS. First version to introduce volume serial number when formatting hard disks and floppy disks (Disk duplication also^{[nb 3]} and when using SYS to make a floppy disk or a partition of a hard drive bootable);^[63] Release date: April, 1989^[64]
  • Version 4.01a (OEM)

MS-DOS 5.x[edit]

MS-DOS 6.x[edit]

• Version 6.0 (Retail) – Online help through QBASIC. Disk compression, upper memory optimization and antivirus included.
• Version 6.2 – SCANDISK as replacement for CHKDSK. Fix serious bugs in DBLSPACE.
• Version 6.21 (Retail) – Stacker-infringing DBLSPACE removed.
• Version 6.22 (Retail) – New DRVSPACE compression.^[67]

MS-DOS 7 (as part of Windows 9x)[edit]

• Windows 95's first retail release included support for VFAT long file names when run in a Windows Virtual-8086 box and 32-bits signed integer errorlevel. New editor. JO.SYS is an alternative filename of the IO.SYS kernel file and used as such for "special purposes". JO.SYS allows booting from either CD-ROM drive or hard disk. Last version to recognize only the first 8.4 GB of a hard disk. The VER internal command reports the Windows version 4.00.950, applications through the MS-DOS API would be reported a version number of 7.00.
• Windows 95's OEM Service Release 2, through Windows 98 Second Edition, added support for the FAT32 file system, and was the last version that could boot to the command line from a hard disk. The VER internal command reports the Windows version 4.00.1111, 4.10.1998, or 4.10.2222 depending on the version of Windows, while applications through the API would report version 7.10.
• Windows Me was the last version based on MS-DOS, and DOS mode was significantly altered in this release. Booting from the hard disk to a command line only was no longer permitted, AUTOEXEC.BAT and CONFIG.SYS files were no longer loaded nor parsed before loading the Windows GUI; booting from floppy disk was still permitted to allow for emergency recovery and this version is included in Windows XP and later versions for creating MS-DOS Startup Disks. The VER internal command reports the Windows version 4.90.3000, or 5.1 when created from newer versions of Windows. Applications requesting the version through the API would report version 8.00.

Microsoft DOS was released through the OEM channel, until Digital Research released DR-DOS 5.0 as a retail upgrade. With PC DOS 5.00.1, the IBM-Microsoft agreement started to end, and IBM entered the retail DOS market with IBM DOS 5.00.1, 5.02, 6.00 and PC DOS 6.1, 6.3, 7, 2000 and 7.1.

Localized versions[edit]

Localized versions of MS-DOS existed for different markets.^[68] While Western issues of MS-DOS evolved around the same set of tools and drivers just with localized message languages and differing sets of supported codepages and keyboard layouts, some language versions were considerably different from Western issues and were adapted to run on localized PC hardware with additional BIOS services not available in Western PCs, support multiple hardware codepages for displays and printers, support DBCS, alternative input methods and graphics output. Affected issues include Japanese (DOS/V), Korean, Arabic (ADOS 3.3/5.0), Hebrew (HDOS 3.3/5.0), Russian (RDOS 4.01/5.0) as well as some other Eastern European versions of DOS.

Competition[edit]

The original MS-DOS advertisement in 1981.

On microcomputers based on the Intel 8086 and 8088 processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from Digital Research, whose CP/M operating system had inspired MS-DOS. In fact, there remains controversy as to whether QDOS was more or less plagiarized from early versions of CP/M code. Digital Research released CP/M-86 a few months after MS-DOS, and it was offered as an alternative to MS-DOS and Microsoft's licensing requirements, but at a higher price. Executable programs for CP/M-86 and MS-DOS were not interchangeable with each other; many applications were sold in both MS-DOS and CP/M-86 versions until MS-DOS became preponderant (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS originally supported the simple .COM, which was modeled after a similar but binary incompatible format known from CP/M-80. CP/M-86 instead supported a relocatable format using the file extension.CMD to avoid name conflicts with CP/M-80 and MS-DOS .COM files. MS-DOS version 1.0 added a more advanced relocatable .EXE executable file format.

Most of the machines in the early days of MS-DOS had differing system architectures and there was a certain degree of incompatibility, and subsequently vendor lock-in. Users who began using MS-DOS with their machines were compelled to continue using the version customized for their hardware, or face trying to get all of their proprietary hardware and software to work with the new system.

In the business world the 808x-based machines that MS-DOS was tied to faced competition from the Unix operating system which ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called Xenix.

In the emerging world of home users, a variety of other computers based on various other processors were in serious competition with the IBM PC: the Apple II, early Apple Macintosh, the Commodore 64 and others did not use the 808x processor; many 808x machines of different architectures used custom versions of MS-DOS. At first all these machines were in competition. In time the IBM PC hardware configuration became dominant in the 808x market as software written to communicate directly with the PC hardware without using standard operating system calls ran much faster, but on true PC-compatibles only. Non-PC-compatible 808x machines were too small a market to have fast software written for them alone, and the market remained open only for IBM PCs and machines that closely imitated their architecture, all running either a single version of MS-DOS compatible only with PCs, or the equivalent IBM PC DOS. Most clones cost much less than IBM-branded machines of similar performance, and became widely used by home users, while IBM PCs had a large share of the business computer market.

Microsoft and IBM together began what was intended as the follow-on to MS-DOS/PC DOS, called OS/2. When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that "DOS is Dead" and stating that version 4 was the last full release. OS/2 was designed for efficient multi-tasking (as was standard in operating systems since 1963) and offered a number of advanced features that had been designed together with similar look and feel; it was seen as the legitimate heir to the "kludgy" DOS platform.

MS-DOS had grown in spurts, with many significant features being taken or duplicated from Microsoft's other products and operating systems. MS-DOS also grew by incorporating, by direct licensing or feature duplicating, the functionality of tools and utilities developed by independent companies, such as Norton Utilities, PC Tools (Microsoft Anti-Virus), QEMM expanded memory manager, Stackerdisk compression, and others.

During the period when Digital Research was competing in the operating system market some computers, like Amstrad PC1512, were sold with floppy disks for two operating systems (only one of which could be used at a time), MS-DOS and CP/M-86 or a derivative of it. Digital Research produced DOS Plus, which was compatible with MS-DOS 2.11, supported CP/M-86 programs, had additional features including multi-tasking, and could read and write disks in CP/M and MS-DOS format.

While OS/2 was under protracted development, Digital Research released the MS-DOS compatible DR DOS 5.0, which included features only available as third-party add-ons for MS-DOS. Unwilling to lose any portion of the market, Microsoft responded by announcing the "pending" release of MS-DOS 5.0 in May 1990. This effectively killed most DR DOS sales until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR DOS 6.0, which sold well until the "pre-announcement" of MS-DOS 6.0 again stifled the sales of DR DOS.

Microsoft had been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD (fear, uncertainty, and doubt) regarding DR DOS. For example, in October 1990, shortly after the release of DR DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in InfoWorld and PC Week. Brad Silverberg, then Vice President of Systems Software at Microsoft and general manager of its Windows and MS-DOS Business Unit, wrote a forceful letter to PC Week (November 5, 1990), denying that Microsoft was engaged in FUD tactics ("to serve our customers better, we decided to be more forthcoming about version 5.0") and denying that Microsoft copied features from DR DOS:

"The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn't be surprising that DRI has heard some of the same requests from customers that we have." – (Schulman et al. 1994).^[69]

The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Much of Microsoft's further contributions to OS/2 also went into creating a third GUI replacement for DOS, Windows NT.

IBM, which had already been developing the next version of OS/2, carried on development of the platform without Microsoft and sold it as the alternative to DOS and Windows.

Legal issues[edit]

As a response to Digital Research's DR DOS 6.0, which bundled SuperStor disk compression, Microsoft opened negotiations with Stac Electronics, vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft part of the Stacker source code. Stac was unwilling to meet Microsoft's terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft's DoubleDisk, using it as the core for its DoubleSpace disk compression.^[70]

MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had disk compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code.

Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages in the Caldera v. Microsoft lawsuit. It was believed that the settlement ran in the order of $150 million, but was revealed in November 2009 with the release of the Settlement Agreement to be $280 million.^[71]

Use of undocumented APIs[edit]

Microsoft also used a variety of tactics in MS-DOS and several of their applications and development tools that, while operating perfectly when running on genuine MS-DOS (and PC DOS), would break when run on another vendor's implementation of DOS. Notable examples of this practice included:

• Microsoft's QuickPascal released in early 1989 was the first MS product that checked for MS-DOS by modifying the program's Program Segment Prefix using undocumented DOS functions, and then checked whether or not the associated value changed in a fixed position within the DOS data segment (also undocumented). This check also made it into later MS products, including Microsoft QuickC v2.5, Programmer's Workbench and Microsoft C v6.0.^[69]
• The AARD code, a block of code in the windows launcher (WIN.COM) and a few other system files of Windows 3.1. It was XOR encrypted, self-modifying, and deliberately obfuscated, using various undocumented DOS structures and functions to determine whether or not Windows really was running on MS-DOS.^[69] 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.^[69]

Demise[edit]

As of 2011^[update], MS-DOS is still used in some enterprises to run legacy applications, such as this US Navy food service management system.

The introduction of Windows 3.0 in 1990, with an easy-to-use graphical user interface, marked the beginning of the end for the command-line driven MS-DOS. With the release of Windows 95 (and continuing in the Windows 9x product line through to Windows Me), an integrated version of MS-DOS was used for bootstrapping, troubleshooting, and backwards-compatibility with old DOS software, particularly games, and no longer released as a standalone product.^[72] 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.

In contrast to the Windows 9x series, the Windows NT-derived 32-bit operating systems developed alongside the 9x series (Windows NT, 2000, XP and newer) do not contain MS-DOS as part of the operating system, as NT is not built as a subsystem running on DOS but an entirely different independent operating system,^[72] but provide a subset of DOS emulation to run DOS applications and provide DOS-like command prompt windows. 64-bit versions of Windows NT line do not provide DOS emulation and cannot run DOS applications natively.^[73]Windows XP contains a copy of the Windows Me boot disk, stripped down to bootstrap only. This is accessible only by formatting a floppy as an "MS-DOS startup disk". Files like the driver for the CD-ROM support were deleted from the Windows Me bootdisk and the startup files (AUTOEXEC.BAT and CONFIG.SYS) no longer had content. This modified disk was the base for creating the MS-DOS image for Windows XP. Some of the deleted files can be recovered with an undelete tool.^[74] When booting up an MS-DOS startup disk made with Windows XP's format tool, the version reports as "Windows Millennium," and not "MS-DOS 8.0" (which was used as the base for Windows Me but never released as a stand-alone product). With Windows Vista the files on the startup disk are dated April 18, 2005 but are otherwise unchanged, including the string "MS-DOS Version 8 Copyright 1981–1999 Microsoft Corp" inside . Starting with Windows 10, the ability to create a DOS startup disk has been removed and so either a virtual machine running MS-DOS or an older version (in a virtual machine or dual boot) must be used to format a floppy disk, or an image must be obtained from an external source. Other solutions include using DOS compatible alternatives, such as FreeDOS or even copying the required files and boot sector themselves.

MS-DOS 6.22 was the last standalone version produced by Microsoft for Intel 8088, Intel 8086, and Intel 80286 processors, which remain available for download via their MSDN,^[75] volume license, and OEM license partner websites, for customers with valid login credentials. MS-DOS is still used in embedded x86 systems due to its simple architecture and minimal memory and processor requirements, though some current products have switched to the still-maintained open-source alternative FreeDOS.

In 2018, Microsoft released the source code for MS-DOS 1.25 and 2.0 on GitHub. The purpose of this, according to Microsoft, is mainly for education and experimentation with historic operating systems and for new programmers to gain an understanding of how low-level software works, both historic and current.

Due to the historical nature of the software, Microsoft will not accept any pull requests to the code; only pull requests for modified and translated documentation will be accepted. Users, however, are allowed and fully encouraged to fork the repository containing the MS-DOS source code and make their own modifications, and do whatever they like with it.

Windows command-line interface[edit]

All versions of Microsoft Windows have had an MS-DOS-like command-line interface (CLI) called Command Prompt. This could run many DOS and variously Win32, OS/2 1.x and POSIX command line utilities in the same command-line session, allowing piping between commands. The user interface, and the icon up to Windows 2000, followed the native MS-DOS interface.

The 16-bit versions of Windows (up to 3.11) ran as a Graphical User Interface (GUI) on top of MS-DOS. With Windows 95, 98, 98 SE and Me, the MS-DOS part was (superficially) integrated, treating the MS-DOS operating system and the Windows GUI as a complete package, though the DOS component could actually stand alone. The command line accessed the DOS command line (usually ) through a Windows module (WINOLDAP.MOD).^{[clarification needed]}

A new line of Windows, (Windows NT), 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 Windows can launch character-mode sessions.

The command session permits running of 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 is done through the NTVDM (NT Virtual DOS Machine). This is a modified SoftPC (a former product similar to VirtualPC), running a modified MS-DOS 5 (NTIO.SYS and NTDOS.SYS). The output is handled by the console DLLs, so that the program at the prompt (, , ), can see the output. 64-bit Windows does not have either the DOS emulation, or the DOS commands EDIT, DEBUG, 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 and other 16-bit commands run in an NTVDM with and initialisation determined by , optionally permitting the use of Win32 console applications and internal commands with an directive.

Win32 console applications use as their command prompt shell. This confusion does not exist under OS/2 because there are separate DOS and OS/2 prompts, and running a DOS program under OS/2 will launch a separate DOS window to run the application.

All versions of Windows for Itanium (no longer sold by Microsoft) and x86-64 architectures no longer include the NTVDM and can therefore no longer natively run DOS or 16-bit Windows applications. There are alternatives in the form of virtual machine emulators such as Microsoft's own Virtual PC, as well as VMware, DOSBox, and others.

Legacy compatibility[edit]

From 1983 onwards, various companies worked on graphical user interfaces (GUIs) capable of running on PC hardware. However, this required duplicated effort and did not provide much consistency in interface design (even between products from the same company).

Later, in 1985, Microsoft Windows 1.0 was released as Microsoft's first attempt at providing a consistent user interface (for applications). The early versions of Windows ran on top of MS-DOS. At first Windows met with little success, but this was also true for most other companies' efforts as well, for example GEM. After version 3.0, Windows gained market acceptance.

Windows 9x used the DOS boot process to launch into protected mode. Basic features related to the file system, such as long file names, were only available to DOS when running as a subsystem of Windows. Windows NT runs independently of DOS but includes NTVDM, a component for simulating a DOS environment for legacy applications.

Related systems[edit]

MS-DOS compatible systems include:

Microsoft manufactured IBM PC DOS for IBM. It and MS-DOS were identical products that eventually diverged starting with MS-DOS version 6.0. Digital Research did not follow Microsoft's version numbering scheme. For example, MS-DOS 4, released in July 1988, was followed by DR DOS 5.0 in May 1990. MS-DOS 5.0 came in April 1991, and DR DOS 6.0 was released the following June.^[76]

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.^[69] Digital Research had to release interim releases to circumvent Windows limitations inserted artificially,^[69] designed specifically to provide Microsoft with a competitive advantage.^[69]

See also[edit]

Notes[edit]

References[edit]

Review

I was riveted: this is a fascinating social history., Nigella Lawson

A magnificent book… what a story this is. Endlessly fascinating., Jewish Chronicle

This story of the family behind the Lyons Corner Houses and many other ventures, its rise and its business demise, is endlessly fascinating and hard to put down. I read it all in one sitting, enjoying the colour and grandeur, whilst spitting with fury at how women were kept out of the financial loop. Full of character and characters, this is a tour de force. -- Rabbi Julia Neuberger

Enthralling... fascinating. Nearly half a century on, the Lyons name and Corner Houses have faded, quite forgotten. I dream of them still., Observer

Five stars. History on a scale at once intimate and grand… extremely readable., The Telegraph

About the Author

Thomas Harding is an author and journalist who has written for the Financial Times, the Sunday Times, the Washington Post and the Guardian, among other publications. He co-founded a television station in Oxford, England, and for many years was an award-winning documentary maker. He also ran a local newspaper in West Virginia, winning the West Virginia Association of Justice’s Journalist of the Year Award, before moving back to England in 2011, where he now lives with his family. He is the author of Hanns and Rudolf, a Sunday Times bestseller and winner of the JQ-Wingate Prize; the internationally acclaimed Kadian Journal: A Father’s Story; The House by the Lake, a Costa Biography Award and Orwell Prize nominee; and Blood on the Page, winner of the 2018 Golden Dagger Award for Non-Fiction.

Microsoft Windows was announced by Bill Gates on November 10, 1983.^[1]Microsoft introduced Windows as a graphical user interface for MS-DOS, which had been introduced a couple of years earlier. In the 1990s, the product line evolved from an operating environment into a fully complete, modern operating system over two lines of development, each with their own separate codebase.

The first versions of Windows (1.0 through to 3.11) were graphical shells that ran from MS-DOS. Later on, Windows 95, though still being based on MS-DOS, was its own operating system, using a 16-bit DOS-based kernel and a 32-bituser space. Windows 95 introduced many features that have been part of the product ever since, including the Start menu, the taskbar, and Windows Explorer (renamed File Explorer in Windows 8). In 1997, Microsoft released Internet Explorer 4 which included the (at the time) controversial Windows Desktop Update. It aimed to integrate Internet Explorer and the web into the user interface and also brought many new features into Windows, such as the ability to display JPEG images as the desktop wallpaper and single window navigation in Windows Explorer. In 1998, Microsoft released Windows 98, which also included the Windows Desktop Update and Internet Explorer 4 by default. The inclusion of Internet Explorer 4 and the Desktop Update led to an anti-trust case in the United States. Windows 98 also includes plug and play, which allows devices to work when plugged in without requiring a system reboot or manual configuration, and USB support out of the box. Windows Me, the last DOS-based version of Windows, was aimed at consumers and released in 2000. It introduced System Restore, Help and Support Center, updated versions of the Disk Defragmenter and other system tools.

In 1993, Microsoft released Windows NT 3.1, the first version of the newly-developed Windows NT operating system. Unlike the Windows 9x series of operating systems, it is a fully 32-bit operating system. NT 3.1 introduced NTFS, a file system designed to replace the older File Allocation Table (FAT) which was used by DOS and the DOS-based Windows operating systems. In 1996, Windows NT 4.0 was released, which includes a fully 32-bit version of Windows Explorer written specifically for it, making the operating system work just like Windows 95. Windows NT was originally designed to be used on high-end systems and servers, however with the release of Windows 2000, many consumer-oriented features from Windows 95 and Windows 98 were included, such as the Windows Desktop Update, Internet Explorer 5, USB support and Windows Media Player. These consumer-oriented features were continued and further extended in Windows XP, which introduced a new theme called Luna, a more user-friendly interface, updated versions of Windows Media Player and Internet Explorer, and extended features from Windows Me, such as the Help and Support Center and System Restore. Windows Vista focused on securing the Windows operating system against computer viruses and other malicious software by introducing features such as User Account Control. New features include Windows Aero, updated versions of the standard games (e.g. Solitaire), Windows Movie Maker, and Windows Mail to replace Outlook Express. Despite this, Windows Vista was critically panned for its poor performance on older hardware and its at-the-time high system requirements. Windows 7 followed two and a half years later, and despite technically having higher system requirements,^[2][3] reviewers noted that it ran better than Windows Vista.^[4] Windows 7 also removed many extra features, such as Windows Movie Maker, Windows Photo Gallery and Windows Mail, instead requiring users download a separate Windows Live Essentials to gain those features and other online services. Windows 8 and Windows 8.1, a free upgrade for Windows 8, introduced many controversial changes, such as the replacement of the Start menu with the Start Screen, the removal of the Aero glass interface in favor of a flat, colored interface as well as the introduction of "Metro" apps (later renamed to Universal Windows Platform apps) and the Charms Bar user interface element, all of which received considerable criticism from reviewers.^[5][6][7]

The current version of Windows, Windows 10, reintroduced the Start menu and added the ability to run Universal Windows Platform apps in a window instead of always in full screen. Windows 10 was well-received, with many reviewers stating that Windows 10 is what Windows 8 should have been.^[8][9][10] Windows 10 also marks the last version of Windows to be traditionally released. Instead, "feature updates" are released twice a year with names such as "Creators Update" and "Fall Creators Update" that introduce new capabilities.

Windows 1.x[edit]

The first independent version of Microsoft Windows, version 1.0, released on November 20, 1985, achieved little popularity. The project was briefly codenamed "Interface Manager" before the windowing system was implemented - contrary to popular belief that it was the original name for Windows and Rowland Hanson, the head of marketing at Microsoft, convinced the company that the name Windows would be more appealing to customers.^[11]

Windows 1.0 was not a complete operating system, but rather an "operating environment" that extended MS-DOS, and shared the latter's inherent flaws and errors.

The first version of Microsoft Windows included a simple graphics painting program called Windows Paint; Windows Write, a simple word processor; an appointment calendar; a card-filer; a notepad; a clock; a control panel; a computer terminal; Clipboard; and RAM driver. It also included the MS-DOS Executive and a game called Reversi.

Microsoft had worked with Apple Computer to develop applications for Apple's new Macintosh computer, which featured a graphical user interface. As part of the related business negotiations, Microsoft had licensed certain aspects of the Macintosh user interface from Apple; in later litigation, a district court summarized these aspects as "screen displays". In the development of Windows 1.0, Microsoft intentionally limited its borrowing of certain GUI elements from the Macintosh user interface, to comply with its license. For example, windows were only displayed "tiled" on the screen; that is, they could not overlap or overlie one another.

Windows 2.x[edit]

Microsoft Windows version 2 came out on December 9, 1987, and proved slightly more popular than its predecessor. Much of the popularity for Windows 2.0 came by way of its inclusion as a "run-time version" with Microsoft's new graphical applications, Excel and Word for Windows. They could be run from MS-DOS, executing Windows for the duration of their activity, and closing down Windows upon exit.

Microsoft Windows received a major boost around this time when AldusPageMaker appeared in a Windows version, having previously run only on Macintosh. Some computer historians^[who?] date this, the first appearance of a significant and non-Microsoft application for Windows, as the start of the success of Windows.

Versions 2.0x used the real-modememory model, which confined it to a maximum of 1 megabyte of memory. In such a configuration, it could run under another multitasker like DESQview, which used the 286protected mode.

Later, two new versions were released: Windows/286 2.1 and Windows/386 2.1. Like prior versions of Windows, Windows/286 2.1 used the real-mode memory model, but was the first version to support the High Memory Area. Windows/386 2.1 had a protected mode kernel with LIM-standard EMSemulation. All Windows and DOS-based applications at the time were real mode, running over the protected mode kernel by using the virtual 8086 mode, which was new with the 80386 processor.

Version 2.03, and later 3.0, faced challenges from Apple over its overlapping windows and other features Apple charged mimicked the ostensibly copyrighted "look and feel" of its operating system and "embodie[d] and generated a copy of the Macintosh" in its OS. Judge William Schwarzer dropped all but 10 of Apple's 189 claims of copyright infringement, and ruled that most of the remaining 10 were over uncopyrightable ideas.^{[citation needed]}

Windows 3.0[edit]

Windows 3.0, released in May 1990, improved capabilities given to native applications. It also allowed users to better multitask older MS-DOS based software compared to Windows/386, thanks to the introduction of virtual memory.

Windows 3.0's user interface finally resembled a serious competitor to the user interface of the Macintosh computer. PCs had improved graphics by this time, due to VGA video cards, and the protected/enhanced mode allowed Windows applications to use more memory in a more painless manner than their DOS counterparts could. Windows 3.0 could run in real, standard, or 386 enhanced modes, and was compatible with any Intel processor from the 8086/8088 up to the 80286 and 80386. This was the first version to run Windows programs in protected mode, although the 386 enhanced mode kernel was an enhanced version of the protected mode kernel in Windows/386.

Windows 3.0 received two updates. A few months after introduction, Windows 3.0a was released as a maintenance release, resolving bugs and improving stability. A "multimedia" version, Windows 3.0 with Multimedia Extensions 1.0, was released in October 1991. This was bundled with "multimedia upgrade kits", comprising a CD-ROM drive and a sound card, such as the Creative LabsSound Blaster Pro. This version was the precursor to the multimedia features available in Windows 3.1 (first released in April 1992) and later, and was part of Microsoft's specification for the Multimedia PC.

The features listed above and growing market support from application software developers made Windows 3.0 wildly successful, selling around 10 million copies in the two years before the release of version 3.1. Windows 3.0 became a major source of income for Microsoft, and led the company to revise some of its earlier plans. Support was discontinued on December 31, 2001.^[12]

OS/2[edit]

During the mid to late 1980s, Microsoft and IBM had cooperatively been developing OS/2 as a successor to DOS. OS/2 would take full advantage of the aforementioned protected mode of the Intel 80286 processor and up to 16 MB of memory. OS/2 1.0, released in 1987, supported swapping and multitasking and allowed running of DOS executables.

IBM licensed Windows's GUI for OS/2 as Presentation Manager, and the two companies stated that it and Windows 2.0 would be almost identical.^[13] Presentation Manager was not available with OS/2 until version 1.1, released in 1988. Its API was incompatible with Windows. Version 1.2, released in 1989, introduced a new file system, HPFS, to replace the FAT file system.

By the early 1990s, conflicts developed in the Microsoft/IBM relationship. They cooperated with each other in developing their PC operating systems, and had access to each other's code. Microsoft wanted to further develop Windows, while IBM desired for future work to be based on OS/2. In an attempt to resolve this tension, IBM and Microsoft agreed that IBM would develop OS/2 2.0, to replace OS/2 1.3 and Windows 3.0, while Microsoft would develop a new operating system, OS/2 3.0, to later succeed OS/2 2.0.

This agreement soon fell apart however, and the Microsoft/IBM relationship was terminated. IBM continued to develop OS/2, while Microsoft changed the name of its (as yet unreleased) OS/2 3.0 to Windows NT. Both retained the rights to use OS/2 and Windows technology developed up to the termination of the agreement; Windows NT, however, was to be written anew, mostly independently (see below).

After an interim 1.3 version to fix up many remaining problems with the 1.x series, IBM released OS/2 version 2.0 in 1992. This was a major improvement: it featured a new, object-oriented GUI, the Workplace Shell (WPS), that included a desktop and was considered by many to be OS/2's best feature. Microsoft would later imitate much of it in Windows 95. Version 2.0 also provided a full 32-bit API, offered smooth multitasking and could take advantage of the 4 gigabytes of address space provided by the Intel 80386. Still, much of the system had 16-bit code internally which required, among other things, device drivers to be 16-bit code as well. This was one of the reasons for the chronic shortage of OS/2 drivers for the latest devices. Version 2.0 could also run DOS and Windows 3.0 programs, since IBM had retained the right to use the DOS and Windows code as a result of the breakup.

Windows 3.1x[edit]

In response to the impending release of OS/2 2.0, Microsoft developed Windows 3.1 (first released in April 1992), which included several improvements to Windows 3.0, such as display of TrueType scalable fonts (developed jointly with Apple), improved disk performance in 386 Enhanced Mode, multimedia support, and bugfixes. It also removed Real Mode, and only ran on an 80286 or better processor. Later Microsoft also released Windows 3.11, a touch-up to Windows 3.1 which included all of the patches and updates that followed the release of Windows 3.1 in 1992.

In 1992 and 1993, Microsoft released Windows for Workgroups (WfW), which was available both as an add-on for existing Windows 3.1 installations and in a version that included the base Windows environment and the networking extensions all in one package. Windows for Workgroups included improved network drivers and protocol stacks, and support for peer-to-peer networking. There were two versions of Windows for Workgroups, WfW 3.1 and WfW 3.11. Unlike prior versions, Windows for Workgroups 3.11 ran in 386 Enhanced Mode only, and needed at least an 80386SX processor. One optional download for WfW was the "Wolverine" TCP/IP protocol stack, which allowed for easy access to the Internet through corporate networks.

All these versions continued version 3.0's impressive sales pace. Even though the 3.1x series still lacked most of the important features of OS/2, such as long file names, a desktop, or protection of the system against misbehaving applications, Microsoft quickly took over the OS and GUI markets for the IBM PC. The Windows API became the de facto standard for consumer software.

Windows NT 3.x[edit]

Meanwhile, Microsoft continued to develop Windows NT. The main architect of the system was Dave Cutler, one of the chief architects of VMS at Digital Equipment Corporation (later acquired by Compaq, now part of Hewlett-Packard).^[14] Microsoft hired him in October 1988 to create a successor to OS/2, but Cutler created a completely new system instead. Cutler had been developing a follow-on to VMS at DEC called Mica, and when DEC dropped the project he brought the expertise and around 20 engineers with him to Microsoft. DEC also believed he brought Mica's code to Microsoft and sued.^[15] Microsoft eventually paid US$150 million and agreed to support DEC's Alpha CPU chip in NT.

Windows NT Workstation (Microsoft marketing wanted Windows NT to appear to be a continuation of Windows 3.1) arrived in Beta form to developers at the July 1992 Professional Developers Conference in San Francisco.^[16] Microsoft announced at the conference its intentions to develop a successor to both Windows NT and Windows 3.1's replacement (Windows 95, codenamed Chicago), which would unify the two into one operating system. This successor was codenamed Cairo. In hindsight, Cairo was a much more difficult project than Microsoft had anticipated and, as a result, NT and Chicago would not be unified until Windows XP—albeit Windows 2000, oriented to business, had already unified most of the system's bolts and gears, it was XP that was sold to home consumers like Windows 95 and came to be viewed as the final unified OS. Parts of Cairo have still not made it into Windows as of 2020: most notably, the WinFS file system, which was the much touted Object File System of Cairo. Microsoft announced that they have discontinued the separate release of WinFS for Windows XP and Windows Vista^[17] and will gradually incorporate the technologies developed for WinFS in other products and technologies, notably Microsoft SQL Server.

Driver support was lacking due to the increased programming difficulty in dealing with NT's superior hardware abstraction model. This problem plagued the NT line all the way through Windows 2000. Programmers complained that it was too hard to write drivers for NT, and hardware developers were not going to go through the trouble of developing drivers for a small segment of the market. Additionally, although allowing for good performance and fuller exploitation of system resources, it was also resource-intensive on limited hardware, and thus was only suitable for larger, more expensive machines.

However, these same features made Windows NT perfect for the LAN server market (which in 1993 was experiencing a rapid boom, as office networking was becoming common). NT also had advanced network connectivity options and NTFS, an efficient file system. Windows NT version 3.51 was Microsoft's entry into this field, and took away market share from Novell (the dominant player) in the following years.

One of Microsoft's biggest advances initially developed for Windows NT was a new 32-bit API, to replace the legacy 16-bit Windows API. This API was called Win32, and from then on Microsoft referred to the older 16-bit API as Win16. The Win32 API had three levels of implementation: the complete one for Windows NT, a subset for Chicago (originally called Win32c) missing features primarily of interest to enterprise customers (at the time) such as security and Unicode support, and a more limited subset called Win32s which could be used on Windows 3.1 systems. Thus Microsoft sought to ensure some degree of compatibility between the Chicago design and Windows NT, even though the two systems had radically different internal architectures. Windows NT was the first Windows operating system based on a hybrid kernel.

As released, Windows NT 3.x went through three versions (3.1, 3.5, and 3.51), changes were primarily internal and reflected back end changes. The 3.5 release added support for new types of hardware and improved performance and data reliability; the 3.51 release was primarily to update the Win32 APIs to be compatible with software being written for the Win32c APIs in what became Windows 95.

Windows 95[edit]

After Windows 3.11, Microsoft began to develop a new consumer oriented version of the operating system codenamed Chicago. Chicago was designed to have support for 32-bit preemptive multitasking like OS/2 and Windows NT, although a 16-bit kernel would remain for the sake of backward compatibility. The Win32 API first introduced with Windows NT was adopted as the standard 32-bit programming interface, with Win16 compatibility being preserved through a technique known as "thunking". A new object oriented GUI was not originally planned as part of the release, although elements of the Cairo user interface were borrowed and added as other aspects of the release (notably Plug and Play) slipped.

Microsoft did not change all of the Windows code to 32-bit, parts of it remained 16-bit (albeit not directly using real mode) for reasons of compatibility, performance, and development time. Additionally it was necessary to carry over design decisions from earlier versions of Windows for reasons of backwards compatibility, even if these design decisions no longer matched a more modern computing environment. These factors eventually began to impact the operating system's efficiency and stability.

Microsoft marketing adopted Windows 95 as the product name for Chicago when it was released on August 24, 1995. Microsoft had a double gain from its release: first, it made it impossible for consumers to run Windows 95 on a cheaper, non-Microsoft DOS, secondly, although traces of DOS were never completely removed from the system and MS DOS 7 would be loaded briefly as a part of the booting process, Windows 95 applications ran solely in 386 enhanced mode, with a flat 32-bit address space and virtual memory. These features make it possible for Win32 applications to address up to 2 gigabytes of virtual RAM (with another 2 GB reserved for the operating system), and in theory prevented them from inadvertently corrupting the memory space of other Win32 applications. In this respect the functionality of Windows 95 moved closer to Windows NT, although Windows 95/98/Me did not support more than 512 megabytes of physical RAM without obscure system tweaks.

IBM continued to market OS/2, producing later versions in OS/2 3.0 and 4.0 (also called Warp). Responding to complaints about OS/2 2.0's high demands on computer hardware, version 3.0 was significantly optimized both for speed and size. Before Windows 95 was released, OS/2 Warp 3.0 was even shipped pre-installed with several large German hardware vendor chains. However, with the release of Windows 95, OS/2 began to lose market share.

It is probably impossible to choose one specific reason why OS/2 failed to gain much market share. While OS/2 continued to run Windows 3.1 applications, it lacked support for anything but the Win32s subset of Win32 API (see above). Unlike with Windows 3.1, IBM did not have access to the source code for Windows 95 and was unwilling to commit the time and resources to emulate the moving target of the Win32 API. IBM later introduced OS/2 into the United States v. Microsoft case, blaming unfair marketing tactics on Microsoft's part.

Microsoft went on to release five different versions of Windows 95:

• Windows 95 - original release
• Windows 95 A - included Windows 95 OSR1 slipstreamed into the installation.
• Windows 95 B - (OSR2) included several major enhancements, Internet Explorer (IE) 3.0 and full FAT32 file system support.
• Windows 95 B USB - (OSR2.1) included basic USB support.
• Windows 95 C - (OSR2.5) included all the above features, plus IE 4.0. This was the last 95 version produced.

OSR2, OSR2.1, and OSR2.5 were not released to the general public, rather, they were available only to OEMs that would preload the OS onto computers. Some companies sold new hard drives with OSR2 preinstalled (officially justifying this as needed due to the hard drive's capacity).

The first Microsoft Plus! add-on pack was sold for Windows 95.

Windows NT 4.0[edit]

Windows NT 4.0 was the successor of 3.5 (1994) and 3.51 (1995). Microsoft released Windows NT 4.0 to manufacturing in July 1996, one year after the release of Windows 95. Major new features included the new Explorer shell from Windows 95, scalability and feature improvements to the core architecture, kernel, USER32, COM and MSRPC.^[18]

Windows NT 4.0 came in four versions:

• Windows NT 4.0 Workstation
• Windows NT 4.0 Server
• Windows NT 4.0 Server, Enterprise Edition (includes support for 8-way SMP and clustering)
• Windows NT 4.0 Terminal Server

Windows 98[edit]

On June 25, 1998, Microsoft released Windows 98 (code-named Memphis). It included new hardware drivers and the FAT32 file system which supports disk partitions that are larger than 2 GB (first introduced in Windows 95 OSR2). USB support in Windows 98 is marketed as a vast improvement over Windows 95. The release continued the controversial inclusion of the Internet Explorer browser with the operating system that started with Windows 95 OEM Service Release 1. The action eventually led to the filing of the United States v. Microsoft case, dealing with the question of whether Microsoft was introducing unfair practices into the market in an effort to eliminate competition from other companies such as Netscape.^[19]

In 1999, Microsoft released Windows 98 Second Edition, an interim release. One of the more notable new features was the addition of Internet Connection Sharing, a form of network address translation, allowing several machines on a LAN (Local Area Network) to share a single Internet connection. Hardware support through device drivers was increased and this version shipped with Internet Explorer 5. Many minor problems that existed in the first edition were fixed making it, according to many, the most stable release of the Windows 9x family.^[20]

Windows 2000[edit]

Microsoft released Windows 2000 on February 17, 2000. It has the version number Windows NT 5.0. Windows 2000 has had four official service packs. It was successfully deployed both on the server and the workstation markets. Amongst Windows 2000's most significant new features was Active Directory, a near-complete replacement of the NT 4.0 Windows Server domain model, which built on industry-standard technologies like DNS, LDAP, and Kerberos to connect machines to one another. Terminal Services, previously only available as a separate edition of NT 4, was expanded to all server versions. A number of features from Windows 98 were incorporated also, such as an improved Device Manager, Windows Media Player, and a revised DirectX that made it possible for the first time for many modern games to work on the NT kernel. Windows 2000 is also the last NT-kernel Windows operating system to lack product activation.

While Windows 2000 upgrades were available for Windows 95 and Windows 98, it was not intended for home users.^[21]

Windows 2000 was available in four editions:

• Windows 2000 Professional
• Windows 2000 Server
• Windows 2000 Advanced Server
• Windows 2000 Datacenter Server

Windows Me[edit]

In September 2000, Microsoft released a successor to Windows 98 called Windows Me, short for "Millennium Edition". It was the last DOS-based operating system from Microsoft. Windows Me introduced a new multimedia-editing application called Windows Movie Maker, came standard with Internet Explorer 5.5 and Windows Media Player 7, and debuted the first version of System Restore – a recovery utility that enables the operating system to revert system files back to a prior date and time. System Restore was a notable feature that would continue to thrive in all later versions of Windows.

Windows Me was conceived as a quick one-year project that served as a stopgap release between Windows 98 and Windows XP. Many of the new features were available from the Windows Update site as updates for older Windows versions (System Restore and Windows Movie Maker were exceptions). Windows Me was criticized for stability issues, as well as for lacking real mode DOS support, to the point of being referred to as the "Mistake Edition."^[22] Windows Me was the last operating system to be based on the Windows 9x (monolithic) kernel and MS-DOS.

Windows XP, Server 2003 series and Fundamentals for Legacy PCs[edit]

On October 25, 2001, Microsoft released Windows XP (codenamed "Whistler"). The merging of the Windows NT/2000 and Windows 95/98/Me lines was finally achieved with Windows XP. Windows XP uses the Windows NT 5.1 kernel, marking the entrance of the Windows NT core to the consumer market, to replace the aging Windows 9x branch. The initial release was met with considerable criticism, particularly in the area of security, leading to the release of three major Service Packs. Windows XP SP1 was released in September 2002, SP2 was released in August 2004 and SP3 was released in April 2008. Service Pack 2 provided significant improvements and encouraged widespread adoption of XP among both home and business users. Windows XP lasted longer as Microsoft's flagship operating system than any other version of Windows, from October 25, 2001 to January 30, 2007 when it was succeeded by Windows Vista.

Windows XP is available in a number of versions:

• Windows XP Home Edition, for home desktops and laptops - lacked features such as joining Active Directory Domain, Remote Desktop Server and Internet Information Services Server.
• Windows XP Professional, for business and power users contained all features in Home Edition.
  • Windows XP Professional N, as above, but without a default installation of Windows Media Player, as mandated by a European Union ruling
• Windows XP Media Center Edition (MCE), released in October 2002 for desktops and notebooks with an emphasis on home entertainment. Contained all features offered in Windows XP Professional and the Windows Media Center. Subsequent versions are the same but have an updated Windows Media Center.
  • Windows XP Media Center Edition 2003
  • Windows XP Media Center Edition 2004
  • Windows XP Media Center Edition 2005, released on October 12, 2004. Included Windows XP Service Pack 2, the Royale Windows Theme and joining a Windows Active Directory Domain is disabled. The Aquarium, Da Vinci, Nature and Space themes are retained from Windows XP Plus!
• Windows XP Tablet PC Edition, for tablet PCs
  • Windows XP Tablet PC Edition 2005
• Windows XP Embedded, for embedded systems
• Windows XP Starter Edition, for new computer users in developing countries
• Windows XP Professional x64 Edition, released on April 25, 2005 for home and workstation systems utilizing 64-bit processors based on the x86-64 instruction set originally developed by AMD as AMD64; Intel calls their version Intel 64. Internally, XP x64 was a somewhat updated version of Windows based on the Server 2003 codebase.
• Windows XP 64-bit Edition, is a version for Intel's Itanium line of processors; maintains 32-bit compatibility solely through a software emulator. It is roughly analogous to Windows XP Professional in features. It was discontinued in September 2005 when the last vendor of Itanium workstations stopped shipping Itanium systems marketed as "Workstations".

Windows Server 2003[edit]

Windows Server 2003 Desktop

On April 25, 2003, Microsoft launched Windows Server 2003, a notable update to Windows 2000 Server encompassing many new security features, a new "Manage Your Server" wizard that simplifies configuring a machine for specific roles, and improved performance. It has the version number NT 5.2. A few services not essential for server environments are disabled by default for stability reasons, most noticeable are the "Windows Audio" and "Themes" services; users have to enable them manually to get sound or the "Luna" look as per Windows XP. The hardware acceleration for display is also turned off by default, users have to turn the acceleration level up themselves if they trust the display card driver.

In December 2005, Microsoft released Windows Server 2003 R2, which is actually Windows Server 2003 with SP1 (Service Pack 1), together with an add-on package. Among the new features are a number of management features for branch offices, file serving, printing and company-wide identity integration.

Windows Server 2003 is available in six editions:

• Web Edition (32-bit)
• Enterprise Edition (32 and 64-bit)
• Datacenter Edition (32 and 64-bit)
• Small Business Server (32-bit)
• Storage Server (OEM channel only).

Windows Server 2003 R2, an update of Windows Server 2003, was released to manufacturing on December 6, 2005. It is distributed on two CDs, with one CD being the Windows Server 2003 SP1 CD. The other CD adds many optionally installable features for Windows Server 2003. The R2 update was released for all x86 and x64 versions, except Windows Server 2003 R2 Enterprise Edition, which was not released for Itanium.

Windows XP x64 and Server 2003 x64 Editions[edit]

On April 25, 2005, Microsoft released Windows XP Professional x64 Edition and Windows Server 2003, x64 Editions in Standard, Enterprise and Datacenter SKUs. Windows XP Professional x64 Edition is an edition of Windows XP for x86-64 personal computers. It is designed to use the expanded 64-bit memory address space provided by the x86-64 architecture.^[23]

Windows XP Professional x64 Edition is based on the Windows Server 2003 codebase, with the server features removed and client features added. Both Windows Server 2003 x64 and Windows XP Professional x64 Edition use identical kernels.^[24]

Windows XP Professionalx64 Edition is not to be confused with Windows XP 64-bit Edition, as the latter was designed for IntelItanium processors.^[25][26] During the initial development phases, Windows XP Professional x64 Edition was named Windows XP 64-Bit Edition for 64-Bit Extended Systems.^[27]

Windows Fundamentals for Legacy PCs[edit]

Windows Fundamentals for Legacy PCs Desktop

In July 2005, Microsoft released a thin-client version of Windows XP Service Pack 2, called Windows Fundamentals for Legacy PCs (WinFLP). It is only available to Software Assurance customers. The aim of WinFLP is to give companies a viable upgrade option for older PCs that are running Windows 95, 98, and Me that will be supported with patches and updates for the next several years. Most user applications will typically be run on a remote machine using Terminal Services or Citrix.

While being visually the same as Windows XP, it has some differences. For example, if the screen has been set to 16 bit colors, the Windows 2000 recycle bin icon and some XP 16-bit icons will show. Paint and some games like Solitaire aren't present too.

Windows Home Server[edit]

Windows Home Server (code-named Q, Quattro) is a server product based on Windows Server 2003, designed for consumer use. The system was announced on January 7, 2007 by Bill Gates. Windows Home Server can be configured and monitored using a console program that can be installed on a client PC. Such features as Media Sharing, local and remote drive backup and file duplication are all listed as features. The release of Windows Home Server Power Pack 3 added support for Windows 7 to Windows Home Server.

Windows Vista and Server 2008[edit]

Windows Vista was released on November 30, 2006 to business customers - consumer versions followed on January 30, 2007. Windows Vista intended to have enhanced security by introducing a new restricted user mode called User Account Control, replacing the "administrator-by-default" philosophy of Windows XP. Vista was the target of much criticism and negative press, and in general was not well regarded, this was seen as leading to the relatively swift release of Windows 7.

One major difference between Vista and earlier versions of Windows, Windows 95 and later, is that the original start button was replaced with the Windows icon in a circle (called the Start Orb). Vista also features new graphics features, the Windows AeroGUI, new applications (such as Windows Calendar, Windows DVD Maker and some new games including Chess, Mahjong, and Purble Place),^[28]Internet Explorer 7, Windows Media Player 11, and a large number of underlying architectural changes. Windows Vista has the version number NT 6.0. Since its release, Windows Vista has had two service packs.

Windows Vista ships in six editions:^[29]

• Starter (only available in developing countries)
• Home Basic
• Home Premium
• Business
• Enterprise (only available to large business and enterprise)
• Ultimate (combines both Home Premium and Enterprise)

All editions (except Starter edition) are currently available in both 32-bit and 64-bit versions. The biggest advantage of the 64-bit version is breaking the 4 gigabyte memory barrier, which 32-bit computers cannot fully access.

Windows Server 2008[edit]

Windows Server 2008, released on February 27, 2008, was originally known as Windows Server Codename "Longhorn". Windows Server 2008 builds on the technological and security advances first introduced with Windows Vista, and is significantly more modular than its predecessor, Windows Server 2003.

Windows Server 2008 ships in ten editions:

• Windows Server 2008 Standard Edition (32-bit and 64-bit)
• Windows Server 2008 Enterprise Edition (32-bit and 64-bit)
• Windows Server 2008 Datacenter Edition (32-bit and 64-bit)
• Windows HPC Server 2008
• Windows Web Server 2008 (32-bit and 64-bit)
• Windows Storage Server 2008 (32-bit and 64-bit)
• Windows Small Business Server 2008 (64-bit only)
• Windows Essential Business Server 2008 (32-bit and 64-bit)
• Windows Server 2008 for Itanium-based Systems
• Windows Server 2008 Foundation Server

Windows 7 and Server 2008 R2[edit]

Windows 7 was released to manufacturing on July 22, 2009, and reached general retail availability on October 22, 2009.^[30][31] It was previously known by the codenames Blackcomb and Vienna. Windows 7 has the version number NT 6.1. Since its release, Windows 7 has had one service pack.

Some features of Windows 7 are faster booting, Device Stage, Windows PowerShell, less obtrusive User Account Control, multi-touch, and improved window management.^[32] Features included with Windows Vista and not in Windows 7 include the sidebar (although gadgets remain) and several programs that were removed in favor of downloading their Windows Live counterparts.

Windows 7 ships in six editions:^[33]

• Starter (available worldwide)
• Home Basic
• Home Premium
• Professional
• Enterprise (available to volume-license business customers only)
• Ultimate

In some countries (Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, United Kingdom, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, and Switzerland)^{[citation needed]}, there are other editions that lack some features such as Windows Media Player, Windows Media Center and Internet Explorer - these editions were called names such as "Windows 7 N." Microsoft focuses on selling Windows 7 Home Premium and Professional. All editions, except the Starter edition, are available in both 32-bit and 64-bit versions. Unlike the corresponding Vista editions, the Professional and Enterprise editions are supersets of the Home Premium edition.

At the Professional Developers Conference (PDC) 2008, Microsoft also announced Windows Server 2008 R2, as the server variant of Windows 7. Windows Server 2008 R2 ships in 64-bit versions (x64 and Itanium) only.

Windows Thin PC[edit]

In 2010, Microsoft released Windows Thin PC or WinTPC, which is a feature-and size-reduced locked-down version of Windows 7 expressly designed to turn older PCs into thin clients. WinTPC is available for software assurance customers and relies on cloud computing in a business network. Wireless operation is supported since WinTPC has full wireless stack integration, but wireless operation may not be as good as the operation on a wired connection.^[34][35]

Windows Home Server 2011[edit]

Windows Home Server 2011 code named 'Vail'^[36] was released on April 6, 2011.^[37] Windows Home Server 2011 is built on the Windows Server 2008 R2 code base and removed the Drive Extender drive pooling technology in the original Windows Home Server release.^[38] Windows Home Server 2011 is considered a "major release".^[36] Its predecessor was built on Windows Server 2003. WHS 2011 only supports x86-64 hardware.

Microsoft decided to discontinue Windows Home Server 2011 on July 5, 2012 while including its features into Windows Server 2012 Essentials.^[39] Windows Home Server 2011 was supported until April 12, 2016.^[40]

Windows 8 and Server 2012[edit]

On October 26, 2012, Microsoft released Windows 8 to the public. One edition, Windows RT, runs on some system-on-a-chip devices with mobile 32-bitARM (ARMv7) processors. Windows 8 features a redesigned user interface, designed to make it easier for touchscreen users to use Windows. The interface introduced an updated Start menu known as the Start screen, and a new full-screen application platform. The desktop interface is also present for running windowed applications, although Windows RT will not run any desktop applications not included in the system. On the Building Windows 8 blog, it was announced that a computer running Windows 8 can boot up much faster than Windows 7.^[41] New features also include USB 3.0 support, the Windows Store, the ability to run from USB drives with Windows To Go, and others. Windows 8 was given the kernel number NT 6.2, with its successor 8.1 receiving the kernel number 6.3. So far, neither has had any service packs yet, although many consider Windows 8.1 to be a service pack for Windows 8.

Windows 8 is available in the following editions:

• Windows 8
• Windows 8 Pro
• Windows 8 Enterprise
• Windows RT

The first public preview of Windows Server 2012 and was also shown by Microsoft at the 2011 Microsoft Worldwide Partner Conference.^[42]

Windows 8 Release Preview and Windows Server 2012 Release Candidate were both released on May 31, 2012.^[43] Product development on Windows 8 was completed on August 1, 2012, and it was released to manufacturing the same day.^[44] Windows Server 2012 went on sale to the public on September 4, 2012. Windows 8 went on sale October 26, 2012.

Windows 8.1 and Windows Server 2012 R2 were released on October 17, 2013. Windows 8.1 is available as an update in the Windows store for Windows 8 users only and also available to download for clean installation.^[45] The update adds new options for resizing the live tiles on the Start screen.^[46]

Windows 10 and Server 2016[edit]

Windows 10 is the current release of the Microsoft Windows operating system. Unveiled on September 30, 2014, it was released on July 29, 2015.^[47] It was distributed without charge to Windows 7 and 8.1 users for one year after release. A number of new features like Cortana, the Microsoft Edge web browser, the ability to view Windows Store apps as a window instead of fullscreen, virtual desktops, revamped core apps, Continuum, and a unified Settings app were all features debuted in Windows 10. Microsoft has announced that Windows 10 will be the last major version of its series of operating systems to be released. Instead, Microsoft will release major updates to the operating system via download or in Windows Update, similar to the way updates are delivered in macOS.^[48]

So far, nine major versions of Windows 10 have been released, with the version 19H2 being the latest stable release, and 20H2 as the latest preview version.

Stable releases[edit]

• Version 1507 (codenamed Threshold 1) was the original version of Windows 10 and released in July 2015.^[49]
• Version 1511, announced as the November Update and codenamed Threshold 2. It was released in November 2015. This update added many visual tweaks, such as more consistent context menus and the ability to change the color of window titlebars. Windows 10 can now be activated with a product key for Windows 7 and later, thus simplifying the activation process and essentially making Windows 10 free for anyone who has Windows 7 or later, even after the free upgrade period ended. A "Find My Device" feature was added, allowing users to track their devices if they lose them, similar to the Find My iPhone service that Apple offers. Controversially, the Start menu now displays "featured apps". A few tweaks were added to Microsoft Edge, including tab previews and the ability to sync the browser with other devices running Windows 10.^[50][51] Kernel version number: 10.0.10586.
• Version 1607, announced as the Anniversary Update and codenamed Redstone 1. It was the first of several planned updates with the "Redstone" codename. Its version number, 1607, means that it was supposed to launch in July 2016, however it was delayed until August 2016. Tons of new features were included in the version, including more integration with Cortana, a dark theme, browser extension support for Microsoft Edge, click-to-play Flash by default, tab pinning, web notifications, swipe navigation in Edge, and the ability for Windows Hello to use a fingerprint sensor to sign into apps and websites, similar to Touch ID on the iPhone. Also added was Windows Ink, which improves digital inking in many apps, and the Windows Ink Workspace which lists pen-compatible apps, as well as quick shortcuts to a sticky notes app and a sketchpad. Microsoft, through their partnership with Canonical, integrated a full Ubuntu bash shell via the Windows Subsystem for Linux. Notable tweaks in this version of Windows 10 include the removal of the controversial password-sharing feature of Microsoft's Wi-Fi Sense service, a slightly redesigned Start menu, Tablet Mode working more like Windows 8, overhauled emoji, improvements to the lock screen, calendar integration in the taskbar, and the Blue Screen of Death now showing a QR code which users can scan to quickly find out what caused the error.^[52] This version of Windows 10's kernel version is 10.0.14393.
• Version 1703, announced as the Creators Update and codenamed Redstone 2. Features for this update include a new Paint 3D application, which allows users to create and modify 3D models, integration with Microsoft's HoloLens and other "mixed-reality" headsets produced by other manufacturers, Windows My People, which allows users to manage contacts, Xbox game broadcasting, support for newly developed APIs such as WDDM 2.2, Dolby Atmos support, improvements to the Settings app, and more Edge and Cortana improvements. This version also included tweaks to system apps, such as an address bar in the Registry Editor, Windows PowerShell being the default command line interface instead of the Command Prompt and the Windows Subsystem for Linux being upgraded to support Ubuntu 16.04.^[53] This version of Windows 10 was released on April 11, 2017 as a free update.^[54]
• Version 1709, announced as the Fall Creators Update and codenamed Redstone 3. It introduced a new design language - the Fluent Design System and incorporates it in UWP apps such as Calculator. It also added new features to the photos application, which were once available only in Windows Movie Maker.
• Version 1803, announced as the April 2018 Update and codenamed Redstone 4 introduced Timeline, an upgrade to the task view screen such that it has the ability to show past activities and let users resume them. The respective icon on the taskbar was also changed to reflect this upgrade. Strides were taken to incorporate Fluent Design into Windows, which included adding Acrylic transparency to the Taskbar and Taskbar Flyouts. The Settings App was also redesigned to have an Acrylic left pane. Variable Fonts were introduced.
• Version 1809, announced as the Windows 10 October 2018 Update and codenamed Redstone 5 among new features, introduced Dark Mode for File Explorer, Your Phone App to link Android phone with Windows 10, new screenshot tool called Snip & Sketch, Make Text Bigger for easier accessibility, and Clipboard History and Cloud Sync.
• Version 1903, announced as the Windows 10 May 2019 Update, codenamed 19H1. It added many new features including the addition of a light theme to the Windows shell and a new feature known as Windows Sandbox, which allows users to run programs in a throwaway virtual window.
• Version 1909, announced as the Windows 10 November 2019 Update, codenamed 19H2. It unlocked many features that were already present, but hidden or disabled, on 1903, such as an auto-expanding menu on Start while hovering the mouse on it, One Drive integration on Windows Search and creating events from the taskbar's clock. Some PCs with version 1903 had already enabled these features without installing 1909.
• Version 2004, named the Windows 10 May 2020 Update, codenamed 20H1. It introduces several new features such as renaming virtual desktops, GPU temperature control and type of disk on task manager, chat-based interface and window appearance for Cortana, cloud reinstalling and quick searches (depends from region) for search home.

Preview versions[edit]

• Version 20H2, expected to be released on the second half of 2020. It includes a graphic mode for Calculator, process architecture view on task manager's Details pane, optional drivers delivery from Windows Update and an updated in-use location icon on taskbar.
• Dev Channel, it flights new features from the "RS_PRERELEASE" branch and isn't tied to any specific release of Windows 10.

Windows Server 2016[edit]

Windows Server 2016 is a release of the Microsoft Windows Server operating system that was unveiled on September 30, 2014. Windows Server 2016 was officially released at Microsoft's Ignite Conference, September 26–30, 2016.^[55]

Windows Server 2019[edit]

Windows Server 2019 is a release of the Microsoft Windows Server operating system.

Windows Server 2019 was announced on March 20, 2018, and the first Windows Insider preview version was released on the same day. It was released for general availability on October 2, 2018.