OS/2OS/2 is an operating system created by Microsoft and IBM and later developed by IBM exclusively. The name stands for "Operating System/2", because it was intended as the preferred operating system for IBM's "Personal System/2 (PS/2)" line of second-generation Personal Computers. OS/2 was intended as a protected-mode successor of MS-DOS and Windows. Notably, basic system calls were modeled after MS-DOS calls, their names even started with Dos and it was possible to link text mode applications in such a way that they could work on both systems (bound programs). Because of this heritage, in terms of look, feel and features, OS/2 is not unlike Windows in many ways; but it also shares similarities with Unix. OS/2 1.0 was released in 1987, as a text mode-only OS. It however featured a rich API for controlling the video display (VIO) and getting keyboard and mouse events, a sort of a protected-mode BIOS. Not surprisingly, the video and keyboard APIs were also available to bound programs on MS-DOS. The promised GUI was introduced with OS/2 1.1 in late 1988. The collaboration between IBM and Microsoft unravelled around the time of the development of version 1.3, when IBM took full responsibility for the project. Microsoft and IBM had originally compromised that IBM would develop OS/2 2.0, while Microsoft would develop OS/2 3.0; but the deal then completely fell apart.\nReportedly, the dispute centered on the question whether to support the Intel 80286 CPU, or the 80386 processor. Eventually, Microsoft's OS/2 3.0 project became Windows NT 3.1, which was released in 1993. Windows NT featured an OS/2 1.x compatibility layer which would let one execute text mode OS/2 1.x applications. The execution of graphical OS/2 1.x applications was possible using an add-on. This OS/2 personality existed until version 5.0, better known as Windows 2000 and was dropped in Windows XP. Microsoft released Windows 3.1 as its response to IBM's OS/2 2.0. Both Windows 95 and OS/2 eventually supported 32-bit APIs. For details and feature comparisons, see the History of Microsoft Windows page. Overall, OS/2 failed to catch on in the consumer market, and is today little used outside certain niche markets where IBM traditionally had a stronghold. For example, many banks, especially Automated Teller Machines, run OS/2 with a customized user interface; French SNCF national railways use OS/2 1.x in dozens of thousands of ticket selling machines. Nevertheless, OS/2 still maintains a small and dedicated community of followers. Although shortly after the release of Warp 4 in 1996, IBM began indicating that OS/2 would eventually be withdrawn, the company has not published a definite end of support date so far. The latest IBM version is 4.52 which was released for both desktop and server systems in December 2001. A company called Serenity Systems has been reselling OS/2 since 2001, calling it eComStation. The latest version is 1.1, released in May 2003. IBM is still delivering fixes and updates on a regular basis. IBM urges customers to migrate their often highly complex applications to e-business technologies such as Java in a platform-neutral manner. Once application migration is completed, IBM recommends to migrate to a different operating system without giving any specific recommendations. Even though some people had hoped that IBM would release OS/2 as open source, this is unlikely to happen since OS/2 contains much third-party code, much of it from Microsoft. Notably, although OS/2 2.0 is often believed to be IBM's own work, a beta version, accompanied by an SDK already had been released by Microsoft in the second half of 1990; OS/2 32-bit executable files have almost exactly the format of Windows 3.0 VxD device drivers (older 16-bit executables have the format of Windows executables). IBM seems mostly responsible for the GUI part of OS/2 (notably, the Presentation Manager API did not change in 2.0), and probably for the divergence in syntax and semantics compared to Windows. This was an underlying cause for the breakup between IBM and Microsoft when Windows 3.0 became much more successful than OS/2. However, open source operating systems such as Linux have already profited from OS/2 indirectly through IBM's release of the JFS file system, which was ported from the OS/2 code base.Technology\nThe graphic system has a layer named Presentation Manager that manages windows, fonts and icons. This is similar in functionality to a non-networked version of X11. On top of this lies the Workplace Shell (WPS), introduced in OS/2 2.0, which is an object-oriented shell allowing the user to access files and printers, and launch programs. WPS follows IBM's Common User Access user interface standards. OS/2 represents objects such as disks, folders, files, program objects, and printers using the System Object Model (SOM), which allows code to be shared among applications, possibly written in different programming languages. A distributed version called DSOM allowed objects on different computers to communicate. DSOM is based on CORBA. SOM is similar to, and a direct competitor to, Microsoft's Component Object Model. SOM and DSOM are no longer being developed. OS/2 also includes a compound document technology called OpenDoc, which was a developed with Apple. OpenDoc is also no longer being developed. The TCP/IP stack is based on the open source BSD stack.See also\n* History of the graphical user interface\n* REXXExternal links
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