Windows is the operating system sold by the Seattle-based company Microsoft. Microsoft, originally christened "Traf-O-Data" in 1972, was renamed "Micro-soft" in November 1975, then "Microsoft" on November 26, 1976.
Microsoft entered the marketplace in August 1981 by releasing version 1.0 of the operating system Microsoft DOS (MS-DOS), a 16-bit command-line operating system
The first version of Microsoft Windows (Microsoft Windows 1.0) came out in November 1985. It had a graphical user interface, inspired by the user interface of the Apple computers of the time. Windows 1.0 was not succesful with the public, and Microsoft Windows 2.0, launched December 9, 1987, did not do much better.
It was on May 22, 1990 that Microsoft Windows became a success, with Windows 3.0, then Windows 3.1 in 1992, and finally Microsoft Windows for Workgroups, later renamed Windows 3.11, which included network capabilities. Windows 3.1 cannot be considered an entirely separate operating system because it was only a graphical user interface running on top of MS-DOS.
On August 24, 1995, Microsoft launched the operating system Microsoft Windows 95. Windows 95 signified Microsoft's willingness to transfer some of MS-DOS's capabilities into Windows, but this new version was based more heavily on 16-bit DOS and retained the limitations of the FAT16 file system, so that it was not possible to use long file names.
After minor revisions of Microsoft Windows 95, named Windows 95A OSR1, Windows 95B OSR2, Windows 95B OSR2.1 and Windows 95C OSR2.5, Microsoft released the next version of Windows on June 25, 1998: Windows 98. Windows 98 natively supported features other than those of MS-DOS but was still based upon it. What's more, Windows 98 suffered from poor memory handling when multiple applications were running, which could cause system malfunctions. A second edition of Windows 98 came out on February 17, 2000; it was named Windows 98 SE (for "Second Edition").
On September 14, 2000, Microsoft released Windows Me (for Millennium Edition), also called Windows Millennium. Windows Millennium was based largely on Windows 98 (and therefore on MS-DOS), but added additional multimedia and software capabilities. Furthermore, Windows Millennium included a system-restore mechanism for returning to a previous state in the event of a crash.
Concurrent with these releases, Microsoft had been selling (since 1992) an entirely 32-bit operating system (which therefore was not based on MS-DOS) for professional use, at a time when business primarily used mainframes. It was Windows NT (for Windows "New Technology"). Windows NT was not a new version of Windows 95 or an improvement on it, but an entirely different operating system
On May 24, 1993, the first version of Windows NT was released. It was called Windows NT 3.1, and was followed by Windows NT 3.5 in September 1994 and Windows 3.51 in June 1995. With Windows NT 4.0, launched for sale on August 24, 1996, Windows NT finally became a true success.
In July 1998, Microsoft released Windows NT 4.0 TSE (Terminal Server Emulation), the first Windows system that allowed terminals to be plugged into a server, i.e. use thin clients to open a session on the server.
On February 17, 2000, the next version of NT 4.0 was renamed Windows 2000 (instead of Windows NT 5.0) in order to highlight the unification of "NT" with the "Windows 9x" systems. Windows 2000 is an entirely 32-bit system with caracteristics of Windows NT, as well as an improved task manager and full compatibility with USB and FireWire peripherals.
Then, on October 25, 2001, Windows XP arrived on the scene. This was a merger of the preceding operating systems.
Finally, on April 24, 2003, a server operating system was released by Microsoft: Windows Server 2003.