Windows 95

Windows 95 (codenamed Chicago) is a consumer version of Windows released by Microsoft. It was designed to be the successor of Windows 3.1 and would be replaced by Windows 98. Microsoft ended support for Windows 95 on 2001-12-31. It improved upon 16-bit Windows by introducing a hybrid 16/32-bit kernel and eliminating the need for an existing installation of MS-DOS, making it a standalone operating system (running alongside MS-DOS). Microsoft focused on improving the usability of Windows with technologies such as Plug-and-Play, long file names (VFAT), the Start Menu, an updated Desktop, Internet Explorer and Mail, built-in networking, and virtual device drivers. Many of the paradigms introduced with Windows 95 still remain in use today.

It was a revolutionary update for Windows, and also the first concerted effort by Microsoft to listen to consumers. Although it was still built upon the solid, if out-dated, foundations of MS-DOS, the average user never saw the MS-DOS prompt unless they actually wanted to. Windows NT was too intensive for most computers of the time, and it was not until after the release of Windows 95 that Win32 applications were widely used and supported.

Development
The development of Windows 95 started in 1992 shortly after the release of Windows 3.1. Pre-release Windows for Workgroups 3.1 builds were forked into the Cougar project, which attempted to build a 32-bit protected mode kernel to be used in the next Windows-on-DOS release (at the time often called Windows 4.0 or Windows 93). The Cougar project was later merged with Jaguar (known as MS-DOS 7.0, also slated for a separate release) into Chicago, which became Windows 95. The Chicago project additionally took a few components from the Cairo project (meant for Windows NT), including the Cairo user interface, and integrated it into the Chicago shell. Internal Microsoft documents from 1992 occasionally refer to the Chicago project as Windows NT Lite.

The first two builds known to exist are the Usability Testing Builds from January 1993, seen in a Microsoft video. The first leaked build is 58s, known as PDK/M4 from August 1993, followed by 73f and 73g (PDK2/M5 from November 1993), 81 (January 1994), 90c (March 1994), and finally beta 1 builds 99, 116 and 122 (May 1994), beta 2 (October 1994) and RC (throughout 1995).