Microsoft Windows is a series of graphical interface operating systems developed, marketed, and sold by Microsoft.
Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). The most recent client version of Windows is Windows 8; the most recent server version is Windows Server 2008 ; the most recent mobile version is Windows Phone 7.5.
Windows 1.0, the first version, released in 1985. Windows 1.0 did not allow overlapping windows. Instead all windows were tiled. Only dialog boxes could appear over other windows.
Windows 2.0 was released in October 1987 and featured several improvements to the user interface and memory management. Windows 2.0 allowed application windows to overlap each other and also introduced more sophisticated keyboard shortcuts.
The early versions of Windows were often thought of as simply graphical user interfaces, mostly because they ran on top of MS-DOS and used it for file system services.
Windows 3.0, released in 1990. Windows 3.0 (1990) and Windows 3.1 (1992) improved the design, mostly because of virtual memory and loadable virtual device drivers (VxDs) that allowed them to share arbitrary devices between multitasked DOS windows.
Windows 95 was released in August 1995, featuring a new user interface, support for long file names of up to 255 characters, and the ability to automatically detect and configure installed hardware (plug and play).
Microsoft's next release was Windows 98 in June 1998. Microsoft released a second version of Windows 98 in May 1999, named Windows 98 Second Edition (often shortened to Windows 98 SE).
In February 2000, Windows 2000 (in the NT family) was released, followed by Windows Me in September 2000 (Me standing for Millennium Edition). Windows Me updated the core from Windows 98, but adopted some aspects of Windows 2000 and removed the "boot in DOS mode" option. It also added a new feature called System Restore, allowing the user to set the computer's settings back to an earlier date.
In October 2001, Microsoft released Windows XP, a version built on the Windows NT kernel that also retained the consumer-oriented usability of Windows 95 and its successors.
On January 30, 2007, Microsoft released Windows Vista. It contains a number of new features, from a redesigned shell and user interface to significant technical changes, with a particular focus on security features. It is available in a number of different editions, and has been subject to some criticism.
On October 22, 2009, Microsoft released Windows 7. Unlike its predecessor, Windows Vista, which introduced a large number of new features, Windows 7 was intended to be a more focused, incremental upgrade to the Windows line, with the goal of being compatible with applications and hardware which Windows Vista was not at the time. Windows 7 has multi-touch support, a redesigned Windows shell with a new taskbar, referred to as the Superbar, a home networking system called HomeGroup, and performance improvements.
On 29 February 2012, Microsoft released Windows 8 Consumer Preview, the beta version of Windows 8, build 8250. For the first time since Windows 95, the Start button is no longer available on the taskbar, though the Start screen is still triggered by clicking the bottom-left corner of the screen and by clicking Start in the Charm. Windows president Steven Sinofsky said more than 100,000 changes had been made since the developer version went public. In the first day of its release, Windows 8 Consumer Preview was downloaded over one million times. Like the Developer Preview, the Consumer Preview is expired on the 15 January 2013.