Microsoft Windows is a computer operating system developed by Microsoft. It was first launched in 1985 as a graphical operating system built on MS-DOS. The initial version was followed by several subsequent releases, and by the early 1990s, the Windows line had split into two separate lines of releases: Windows 9x for consumers and Windows NT for businesses and enterprises. Since Windows XP, multiple further versions of Windows have been released, the most recent of which is Windows 11.