Microsoft Windows
Screenshot of Windows Vista Ultimate (Build 6000).
Company/developer	Microsoft Corporation
OS family	MS-DOS/9x-based, Windows CE, Windows NT
Source model	Closed source / Shared source
Stable release	Client: Windows Vista SP1 NT 6.0.6001 (February 4, 2008) Server: Windows Server 2008 NT 6.0.6001 (February 27, 2008) [+/-]
Preview release	[+/-]
License	MS-EULA
Working state	Publicly released
Website	www.microsoft.com/windows The box art of Windows 1.0; the first version that Microsoft released to the public. The term Windows collectively describes any or all of several generations of Microsoft (MS) operating system (OS) products. These products are generally categorized as follows: 16-bit operating environments The early versions of Windows were often thought of as just graphical user interfaces, mostly because they ran on top of MS-DOS and used it for file system services.[3] However, even the earliest 16-bit 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) for applications. Unlike MS-DOS, Windows allowed users to execute multiple graphical applications at the same time, through cooperative multitasking. Finally, 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, and data segments moved in memory when a given application had relinquished processor control, typically waiting for user input.[citation needed] 16-bit Windows versions include Windows 1.0 (1985), Windows 2.0 (1987) and its close relatives, Windows/286-Windows/386.