IBM OS/2, operating system introduced in 1987 by IBM and Microsoft to operate the second-generation line of IBM personal computers, the PS/2 (Personal System/2). Although initially IBM and Microsoft worked together on OS/2, the companies parted ways after disputes arose regarding how the system would be upgraded. Microsoft believed its Windows program would be the future of operating systems, but IBM was determined to continue work on OS/2. IBM worked alone on the project after 1992.
IBM OS/2 was intended to replace the older disk operating system (DOS), which, with the development of the Intel Corporation 80286 microchips in the mid-1980s, was growing increasingly obsolete. OS/2 combined a new graphical user interface (GUI) with features previously available only on mainframe computers. It shared similarities with other operating systems, including Microsoft Windows, UNIX, and Xenix, a variant of UNIX.
Simultaneously, Microsoft continued to develop the Windows operating system, whose popular third iteration (Windows 3.0) contained some of the GUI elements developed for OS/2. Despite later basing some Windows NT and Windows 95 developments on code written for IBM and OS/2, Microsoft soon discontinued development of further interface features for OS/2. The companies split in what observers described as a “divorce.”
With Microsoft focusing its efforts on Windows, IBM turned to Commodore Business Machines for interface development and borrowed GUI design ideas from the Commodore AmigaOS. In version OS/2 2.0, released in March 1992, the Workplace Shell desktop environment was created and became a GUI standard, and future OS/2 iterations ran Windows applications with a reliability that led IBM to label the system “crash proof.” The Workplace Shell was considered a notable improvement and featured object-oriented programming for the first time in an operating system. The Workplace Shell also introduced features such as the ability to drag and drop icons into folders, right-click on icons for more options, and drag icons to perform actions such as printing. However, because computers at the time had lower random-access memory (RAM) capacity, consumers often had to upgrade their memory to gain the full benefits of the Workplace Shell, which was a hurdle to OS/2 becoming the mainstream option.
In 1994 IBM introduced a new version, OS/2 Warp, which was the most popular version of OS/2. The system was lauded for being relatively simple and used a 32-bit OS (while still supporting DOS), unlike Windows systems, which continued to use a 16-bit DOS. OS/2, however, failed to acquire a share of the mass market. It survived in IBM-dominated niche markets such as automated teller machines (ATMs), but the company halted production in 2005 and support in 2006. A large part of its failure to become mainstream stemmed from competition with Microsoft, which aggressively sought to dominate the market with its Windows operating systems. Users and developers still loyal to OS/2 support releasing the software as open-source, but Microsoft retains rights to some of the code, and the security of ATMs could be compromised. In 2001 IBM licensed OS/2 to Serenity Systems (and later XEU.com), which sold it as eComStation, and in 2015 to Arca Noae, which sold it as ArcaOS.