Editing Windows 9x (section)

===Windows 95===
{{main|Windows 95}}
[[File:Microsoft Windows 95 logo.svg|thumb|right|Wordmark logo for Windows 95]]
After [[Windows 3.1|Windows 3.11]], [[Microsoft]] began to develop a new consumer oriented version of the operating system code-named Chicago. Chicago was designed to have support for 32-bit preemptive multitasking, that of which was available in OS/2 and Windows NT, although a 16-bit kernel would remain for the sake of backward compatibility. The Win32 [[Application programming interface|API]] first introduced with Windows NT was adopted as the standard 32-bit programming interface, with Win16 compatibility being preserved through a technique known as "[[Thunk (compatibility mapping)|thunking]]". A new GUI was not originally planned as part of the release, although elements of the Cairo user interface were borrowed and added as other aspects of the release (notably Plug and Play) slipped (and indeed after Cairo was cancelled 5 years in development).

Microsoft did not change all of the Windows code to 32-bit; parts of it remained 16-bit (albeit not directly using [[real mode]]) for reasons of compatibility, performance and development time. Additionally it was necessary to carry over design decisions from earlier versions of Windows for reasons of backwards compatibility, even if these design decisions no longer matched a more modern computing environment. These factors immediately began to impact the operating system's efficiency and stability.

Microsoft marketing adopted [[Windows 95]] as the product name for Chicago when it was released on August 24, 1995.

Microsoft went on to release five different versions of Windows 95:
* Windows 95 – original release (RTM)
* Windows 95 A – included Windows 95 [[OEM Service Release 2#Editions|OSR]]1 [[Slipstream (computing)|slipstreamed]] into the installation.
* Windows 95 B – (OSR2) included several major enhancements, [[Internet Explorer]] (IE) 3.0 and full [[FAT32]] file system support.
* Windows 95 B USB – (OSR2.1) included basic [[Universal Serial Bus|USB]] support.
* Windows 95 C – (OSR2.5) included all the above features, plus IE 4.0. This was the last 95 version produced.

OSR2, OSR2.1, and OSR2.5 ("OSR" being an initialism for "OEM Service Release") were not released to the general public, rather, they were available only to [[Original equipment manufacturer|OEMs]] that would preload the OS onto computers. Some companies sold new hard drives with OSR2 preinstalled (officially justifying this as needed due to the hard drive's capacity).

The first [[Microsoft Plus!]] add-on pack was sold for Windows 95.