OS/2 is a multi-tasking, 32-bit, speedy operating system produced by IBM.

At its beginnings, OS/2 was a joint project by Microsoft and IBM. OS/2 by Microsoft would have Microsoft branding on it and OS/2 by IBM would have IBM branding on it. This went on until Microsoft created Windows NT, where the two parties split. This was around OS/2 version 1.3. Windows NT and OS/2 are remarkably similar, even to this day with Windows NT 5.1 (2000) and NT 5.2 (XP).

OS/2 version 1.0 was not graphical at all. Yet it allowed for multi-tasking and was compatible with most DOS applications and commands. Version 1.1 was the first version of OS/2 to have a graphical user interface, albeit an extremely simple one. The GUIs of 1.1 and 1.2 were very similar to the interfaces of Windows versions 2 and 3. This was only to be expected with the joint MS/IBM development. OS/2 version 2.0, compared to the 1.x versions, was somewhat like Windows 95 compared to Windows 3.11. Version 2 brought symmetric multiprocessing (multiple CPU support), Windows 3.x application compatibility, and a revamped user interface. Version 3 - or 'Warp' - was released with Internet support, and extensive network support. The most commonly used OS/2 version nowadays used is version 4, 'Merlin', with built-in voice dictation software, enhanced user interface, OpenGL and Java support.

OS/2 in general is an extremely nice OS, renowned for its stability, and configurable to a great degree, and many applications can be run on it, both natively, and with its Windows compatibility. Project Odin, which is in development, will support 32-bit windows applications.

OS/2 is still available from IBM.