Microsoft Windows

Windows is a proprietary graphical operating system developed and marketed by Microsoft. Windows is grouped into families that cater to particular sectors of the computing industry – Windows for personal computers, Windows Server for servers, and Windows IoT for embedded systems. Windows itself is further grouped into editions that cater to different users – Home for home users, Professional for advanced users, Education for schools, and Enterprise for corporations. Windows is sold both as a consumer retail product and to computer manufacturers, who bundle and distribute it with their systems.

The first version of Windows, Windows 1.0, was released on November 20, 1985 as a graphical operating system shell for MS-DOS in response to growing interest in graphical user interfaces (GUIs). The name Windows is a reference to the windowing system in GUIs. The 1990 release of Windows 3.0 catapulted its market success and led to the launch of various other product families, including the (now-defunct) Windows Mobile, Windows Phone, and Windows CE/Embedded Compact.

Windows is the most popular desktop operating system in the world, with a 80% market share as of February 2026, and the second-most popular operating system overall, behind Android. As of August 2025, Windows 11 is the most used desktop version of Windows, with a market share of 53%.

Product line

All members of the Windows product family are, as of 2026, based on Windows NT. The first version of Windows in that product line, Windows NT 3.1, was intended for server computing and corporate workstations. It now consists of four sub-families that tend to be released almost simultaneously and share the same kernel.

• Windows (unqualified): For a consumer or corporate workstation or tablet. The latest version is Windows 11. Its main competitors are macOS by Apple and Linux for personal computers and iPadOS and Android for tablets (cf. Usage share of operating systems § Market share by category).
  • Of note: "Windows" refers to both the overall product line and this sub-family of it.
• Windows Server: For a server computer. The latest version is Windows Server 2025. Unlike its client sibling, it has adopted a strong naming scheme. The main competitor of this family is Linux. (cf. Usage share of operating systems § Market share by category)
• Windows IoT (previously Windows Embedded): For IoT and embedded computers. The latest version is Windows 11 IoT Enterprise. Like Windows Server, the main competitor of this family is Linux. (cf. Usage share of operating systems § Market share by category)
• Windows PE: A lightweight version of Windows designed to operate as a live operating system, used for installing Windows on bare-metal computers (especially on many computers at once), recovery, or troubleshooting purposes. The latest version is Windows PE 10.

These top-level Windows families are no longer actively developed:

• MS-DOS-based versions of Windows, including Windows 1.0, Windows 2.0, Windows 3.x, and Windows 9x: The original top-level family of Windows prior to Windows NT, aimed at consumers. These versions had a monolithic kernel that uses MS-DOS as a foundation, with Windows 95 and above having its own kernel. The last version was Windows Me; the family was discontinued after the release of Windows XP, with all consumer-oriented versions of Windows afterwards being based on the Windows NT kernel.
• Windows Mobile: Windows Mobile was a mobile phone and PDA operating system and the predecessor to Windows Phone. The first version was Pocket PC 2000; the third version, Windows Mobile 2003, was the first version to adopt the Windows Mobile trademark. The last published version was Windows Mobile 6.5.
• Windows Phone: Sold only to smartphone manufacturers. The first version was Windows Phone 7, followed by Windows Phone 8 and Windows Phone 8.1. It was succeeded by Windows 10 Mobile, which is also defunct.
• Windows Embedded Compact: Most commonly known by its former name, Windows CE, it is a hybrid kernel operating system optimized for low power and memory systems, with OEMs able to modify the UI to suit their needs. The final version was Windows Embedded Compact 2013, and it is succeeded by Windows IoT.

History

The term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are generally categorized as follows:

Early versions

The history of Windows dates back to 1981 when Microsoft started work on a program called "Interface Manager". The name "Windows" comes from the fact that the system was one of the first to use graphical boxes to represent programs; in the industry, at the time, these were called "windows" and the underlying software was called "windowing software." It was announced in November 1983 (after the Apple Lisa, but before the Macintosh) under the name "Windows", but Windows 1.0 was not released until November 1985. Windows 1.0 was to compete with Apple's operating system, but achieved little popularity. Windows 1.0 is not a complete operating system; rather, it extends MS-DOS. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Components included Calculator, Calendar, Cardfile, Clipboard Viewer, Clock, Control Panel, Notepad, Paint, Reversi, Terminal and Write. Windows 1.0 does not allow overlapping windows. Instead, all windows are tiled. Only modal dialog boxes may appear over other windows. Microsoft sold as included Windows Development libraries with the C development environment, which included numerous windows samples.

Windows 2.0 was released in December 1987, and was more popular than its predecessor. It features several improvements to the user interface and memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights (eventually settled in court in Microsoft's favor in 1993). Windows 2.0 also introduced more sophisticated keyboard shortcuts and could make use of expanded memory.

Windows 2.1 was released in two different versions: Windows/286 and Windows/386. Windows/386 uses the virtual 8086 mode of the Intel 80386 to multitask several DOS programs and the paged memory model to emulate expanded memory using available extended memory. Windows/286, in spite of its name, runs on both Intel 8086 and Intel 80286 processors. It runs in real mode but can make use of the high memory area.

In addition to full Windows packages, there were runtime-only versions that shipped with early Windows software from third parties and made it possible to run their Windows software on MS-DOS and without the full Windows feature set.

The early versions of Windows are often thought of as graphical shells, mostly because they ran on top of MS-DOS and used it for file system services. However, even the earliest Windows versions already assumed many typical operating system functions; notably, having their own executable file format and providing their own device drivers (timer, graphics, printer, mouse, keyboard and sound). Unlike MS-DOS, Windows allowed users to execute multiple graphical applications at the same time, through cooperative multitasking. Windows implemented an elaborate, segment-based, software virtual memory scheme, which allowed it to run applications larger than available memory: code segments and resources were swapped in and thrown away when memory became scarce; data segments moved in memory when a given application had relinquished processor control.

Windows 3.x

Windows 3.0, released in 1990, improved the design, mostly because of virtual memory and loadable virtual device drivers (VxDs) that allow Windows to share arbitrary devices between multi-tasked DOS applications. Windows 3.0 applications can run in protected mode, which gives them access to several megabytes of memory without the obligation to participate in the software virtual memory scheme. They run inside the same address space, where the segmented memory provides a degree of protection. Windows 3.0 also featured improvements to the user interface. Microsoft rewrote critical operations from C into assembly. Windows 3.0 was the first version of Windows to achieve broad commercial success, selling 2 million copies in the first six months.

Windows 3.1, made generally available on March 1, 1992, featured a facelift. In October 1992, Windows for Workgroups, a special version with integrated peer-to-peer networking features, was released. It was sold along with Windows 3.1. Support for Windows 3.1 ended on December 31, 2001.

Windows 3.2, released in 1994, is an updated version of the Chinese version of Windows 3.1. The update was limited to this language version, as it fixed only issues related to the complex writing system of the Chinese language. Windows 3.2 was generally sold by computer manufacturers with a ten-disk version of MS-DOS that also had Simplified Chinese characters in basic output and some translated utilities.