OS / 2 ( Operating System / 2 - initially at IBM Germany also BS / 2 for OS / 2) is a multi-tasking operating system for the PC. It was originally developed jointly as the successor to DOS from IBM and Microsoft. After Microsoft 1991, the cooperation ended in order to devote himself instead of Windows development, IBM OS / 2 continued to develop alone. 2005, the distribution and the basic development of IBM were hired under the brand name eComStation operating system that can be developed by third parties.

  • 7.1 16 -bit versions
  • 7.2 32 -bit versions



In January 1983, Microsoft began development on a version of MS- DOS, which could be not only a program, but several programs simultaneously. This was later published under the name MS- DOS 4.0. However, this version of MS- DOS had some limitations. The multitasking capabilities were limited to applications that were developed specifically for this version of MS- DOS; otherwise could not simply a standard MS -DOS application to run. In addition, had, since the operating system completely ran in real mode, all applications share the conventional memory of 640 KB. Because of these limitations, this version of MS- DOS did not appear in the commercial, but was exclusively licensed to certain OEMs.

Microsoft developed the operating system subsequently. To resolve the limitations of the earlier version, the protection mode of the 80286 processor should be exploited. Microsoft signed to a contract with IBM, in which both companies agreed, the operating system, now under the name CP / DOS known to develop together. At the end of the development towards the operating system underwent a re- change of name was called the OS / 2

The 80286 had a big problem: Although the processor from real mode could switch into protection mode, the reverse path, ie to switch from protected mode back to real mode, however, was not provided. However, this was necessary in order to continue to maintain compatibility with DOS applications that can only run in real mode. This problem could only be solved when a way was found, the processor reset so that he was in real mode again.

On April 2, 1987 Microsoft and IBM announced the new operating system officially. The first version should be as DOS text-based, a later version should then contain a derivative of Microsoft Windows graphical user interface called Presentation Manager. At the same time, Microsoft announced a development kit for the new operating system, which should be available for $ 3,000. This development kit was released two months later.

OS / 2 1.x

Earlier than initially announced, IBM released the first version of OS / 2 on 4 December 1987 at a price of 325 USD. Just two weeks later also appeared Microsoft's version of OS / 2 While IBM OS / 2 sales directly, Microsoft licensed the operating system to OEMs continue to deliver up there with their computers and adapting accordingly. The system requirements of the operating system appeared on four floppy disks were a 80286 processor with at least 2 MB of RAM and 5 MB of disk space. The first version looked very similar due to the lack of graphical user interface DOS, however, including concealed a multi-tasking operating system that can manage up to 12 OS/2-Sitzungen the same time and supports up to 16 MB of memory. In addition, OS / 2, a further meeting at which most DOS applications could be executed bot. In July 1988, IBM introduced the OS / 2 Extended Edition out at the price of 795 USD, which contained additional database and communication programs.

However, there was also criticism. So be it, although given the large number of computers with 80286 processors understandable that OS / 2 has been developed for this processor, but has since been the 80386 published, the numerous advantages over the 80286 bot. In addition, the operating system lacks a powerful file system - OS / 2 continued to use the acquired from DOS FAT16 file system that did not support long file names and was limited in the former version to a maximum partition size of 32 MB. In general, it was said that OS / 2 from DOS would offer no advantages, as long as there is no software for the new operating system.

On 31 October 1988, Version 1.1 was released OS / 2, which contained the long-awaited graphical user interface for the first time. However, this was not the only novelty: OS / 2 now supported partitions that are larger than 32 MB. One of the first applications for the new interface counted Borland Sidekick software package that came from November to the operating system. The now had grown to five floppy OS / 2 1.1 had similar system for the previous version, but required 8 MB ​​of hard disk space. One widespread dissemination of the operating system were at that time mainly missing drivers in the way, especially printer drivers were available to the operating system when only very sparse.

OS / 2 1.2 was followed in September 1989 This version first offered the possibility of so-called installable file systems.; that are loaded similar to device drivers at boot time and can in principle allow access to any file systems. One of the installable file systems, HPFS is included with OS / 2 1.2: HPFS is more efficient than the previous FAT file system, it also supports long file names and partitions that are larger than 2 gigabytes. In addition, any data called extended attributes are appended to files. However, there is no backward compatibility; DOS can not access HPFS partitions and for DOS and older OS/2-Anwendungen are files that use long file names, not visible. In addition, OS / 2 1.2 includes an updated user interface and some additional applications.

The version 1.3 of OS / 2 was released in November 1990. This contained hardly any innovations, but was merely an improved version of OS / 2 1.2, which reduced system and included more drivers. However, the resonance of this version was low.

Separation of the two development partners

From the beginning, the relationship between the two companies was strained. IBM and Microsoft were two different companies that pursue different goals. Microsoft wanted to OS / 2, similar to DOS and Windows, making it available as a software platform for many different PCs, IBM, however, wanted to OS / 2 boost sales of your own computer, especially the PS/2-Produktreihe. The developers of both companies were often involved in mutual conflict. IBM took advantage of lines of code as a measure of the productivity of developers; Microsoft's developers, however, wrote a concise and efficient code and were characterized from IBM's point of view as unproductive. Microsoft's developers again complained about the bureaucracy on the part of IBM. Microsoft wanted to quickly OS / 2 adapt to the 80386 processor, but IBM stopped due to customer promise, however, and continue propagating the 80286 version.

Tensions finally erupted when Windows 3.0 was released and was a huge success. Within four years, OS / 2 sold only 300,000 copies, Windows 3.0, however, reached after a year almost 3 million copies. First it was said that IBM should have sole leadership at the next version of OS / 2, version 2.0, while Microsoft developed over the next version 3.0. Finally, Microsoft announced the development of OS / 2 to completely and used the resources to develop a new operating system called Windows NT.

OS / 2 2.x

Accompanied by a large advertising campaign now published the on his own asked IBM OS / 2 2.0 on 1 April 1992, the company called OS / 2 as "a better DOS than DOS and a better Windows than Windows" ( German: . " Better DOS than DOS and a better Windows than Windows "). OS / 2, was now a 32 -bit operating system, the capabilities of the 80386 exploited, even though the operating system also contained a large part of the 16-bit code. The operating system was first run multiple DOS applications in parallel and also the occasion to launch Windows applications in a special Win-OS/2-Umgebung, either directly embedded as a window into the OS/2-Umgebung or in full screen mode could be performed. The full screen mode was faster, but limited due to the lack of support for video card drivers to 640 × 480 and 16 colors. In addition, the Win-OS/2-Umgebung supported only the standard mode, which applications required the 386 - enhanced mode excluded.

OS / 2 2.0 replaced the presentation manager by the new Workplace Shell. The concept of the Workplace Shell follows the paradigm that everything is an object, such as icons, windows, or the desktop background, and can be adjusted by methods such as drag and drop. The user interface was considered to be extremely flexible, but at the same time to learn to be difficult. The Workplace Shell also noted the open applications on shutdown and started it again, once the operating system booted up again.


In the home OS / 2 was because of its stability and the already popular on computers with I286 processor efficient multitasking as a basis for mailboxes. The version of OS / 2 Warp 3 was the mid-1990s on the computers of some computer chains (including Vobis, Escom ) pre-installed. However, this was a largely restricted to Germany phenomenon. There, OS / 2 mid-1990s, was able to win a certain market share. Worldwide, OS / 2, however, could never prevail against Windows, because it turned included higher hardware requirements. In particular, at least 8 MiB RAM were necessary in order to really leverage the power can. This was at that time still quite expensive. Many pre-installations had the problem that the computer had only 4 MiB of RAM and therefore were very slow because the system was constantly busy with swapping to disk.

Through the bad and contradictory marketing of IBM failure was predetermined on the market; IBM applied for OS / 2 on the one hand, as a solution for young computer freaks, but on the other hand had a large part of corporate customers, who so completely different requirements. Games, there were comparatively few, useful office applications by only a few manufacturers, including Lotus 1-2-3 and StarOffice. The office applications from Microsoft were indeed available, but these were 16- bit based, much slower and less stable than their Windows counterparts.

OS / 2 should also be developed for the PowerPC processor. It is also a version was under discussion which should run on Macintosh computers from Apple. A variant should replace the elderly Mac OS, which was not able to pre-emptive multitasking. Apple is very quickly got out of this development so that a broader base for the operating system was not available. In the computer week it was said, for example: "According to InfoWorld is a change between Mac OS and OS / 2 may be possible for Power PC. Here, the kernel of the Apple operating system will be replaced and turned off those memory block that contains all Macs parts of the OS " This was then clarified: ". On Power PCs running at the time the operating systems Mac OS 7.1.2 and Windows NT, soon probably IBM's OS / 2 " that it did not come so far, was another reason for the failure of OS / 2

OS / 2 had from the outset properties that were implemented later in other PC operating systems. One example is the memory protection, which prevents a faulty application pulls another program or the entire system affected. In addition preemptive multitasking. Another example is the ability for different programs to keep multiple versions of a program library at the same time ( for compatibility reasons ). This possibility offered only with Microsoft Windows NT 3.1.

Using the operating system today

Meanwhile, OS / 2 is rarely used in the home area due to the lower supply current software, and also for banks, insurance companies and airlines is the utilization decline. New installations are usually realized with the eComStation distribution. In addition, it is still in the field of home automation and security technology use. It also fills a niche in the manufacturing industry.

So far remained OS / 2 and eComStation (eCS ) virtually spared from dangers such as viruses, Trojans and worms. However, this is less due to the system architecture and more to the small market share.

Current Situation

IBM announced in the winter of 2002 to the end of the private client sales of OS / 2. Business customers were initially continue to be supplied by IBM with OS / 2. The support of IBM finally ended on 31 December 2006. IBM advises its customers to switch to Linux.

The distribution was taken over by Serenity Systems as a licensed product under the name eComStation in 2001. However, there has no access to the source code, so that further developments of the kernel are not expected. For the working surface has been further developed, simplifies installation, renewed parts of the operating system and with the help of a dedicated community of users, the software base for eComStation and OS / 2 extended considerably.

There are also efforts to develop a compatible OS / 2 open source operating system. The project is called osFree and is still in a very early stage.

Presentation manager

The introduced with version 1.1 graphical user interface as a presentation manager (English Presentation Manager, PM ) and corresponds to the IBM SAA and CUA guidelines. From version 2.0, the work surface ( engl. Workplace Shell, WPS ) was used as an object- oriented user interface which is based on object technology SOM. The design of the WPS had a problem: There was for user input only one message queue. Blocks misapplication this, there is no way to communicate with the operating system.

A project to bring the WPS on a new operating system foundation, called Voyager.

Windows and OS / 2

OS / 2 was in addition specially developed for OS / 2 programs in multiple virtual machine MS -DOS programs, and by means of WinOS / 2 run Windows 3.1 programs. With Win32s and especially the Odin project, it is possible to use some Win32 programs within the OS/2-Umgebung. About Virtual PC that was available prior to the acquisition of Connectix by Microsoft for OS / 2, or Bochs can also start a complete Win32 environment.

For easy conversion of Windows in OS/2-Anwendungen the interface Open32 exists. There are also libraries and development tools that support the porting of Unix applications.

Revision history

16 -bit versions

  • IBM IBM OS / 2 1.0 Standard version - December 1987 Text Mode
  • Extended version - July 1988 Communication Manager and Database Manager
  • Standard version - October 1988 for the first time with presentation manager
  • Extended version - the beginning of 1989, in addition to LAN Requester
  • Standard version - November 1989 Installable File Systems, HPFS
  • Extended version - January 1990
  • Standard version - November 1990
  • Extended Version - February 1991
  • Microsoft ( OEM) Microsoft OS / 2 1.0 - November 1987
  • Microsoft OS / 2 1.1 - October 1988 with Presentation Manager
  • Microsoft OS / 2 1.2 - November 1989, support for HPFS
  • Microsoft OS / 2 1.3 - November 1990, the basis for the MS LAN Manager 2.1, already with HPFS386

32 -bit versions

  • IBM IBM OS / 2 2.0 Limited Edition - 1991 pre-release version
  • IBM OS / 2 2.0 - March 31, 1992, 32 bit, i386 -based.
  • IBM OS / 2 2.1 - May 1993
  • IBM OS / 2 2.1 for Windows - December 1993, an OS / 2 2.1, 3.0 Warp 3.1 without Windows emulation. The Original-Windows-3.1/3.11-Installation was integrated here. The same applies to OS / 2 Warp 3.0 for Windows.
  • IBM OS / 2 2.11 - February 1994
  • IBM OS / 2 Warp 3.0 - September 1994
  • IBM OS / 2 Warp 3.0 for Windows - October 1994
  • IBM OS / 2 2.11 SMP - December 1994, Supports SMP to 16 processors
  • IBM OS / 2 Warp Connect 3.0 - 1995
  • IBM OS / 2 Warp Server 4.0 Aurora - 1996, base system was OS / 2 Warp 3.0 Connect with the latest bug fixes and the latest version of the TCP / IP stack. There was a standard and an advanced version. The latter contained more network tools and the file system HPFS386.
  • IBM OS / 2 Warp 4, Merlin - September 1996 OpenGL support
  • IBM Workspace on Demand 1.0 - 1997
  • IBM Workspace on Demand 2.0 - 1999
  • IBM OS / 2 Warp Server for e -business ( 4:50 ) - 1999
  • IBM OS / 2 Warp Convenience Package 1 4:51 - December 2000
  • IBM OS / 2 Warp Convenience Package 2 4:52 - January 2002
  • EComStation 1.0 - 2001
  • EComStation 1.1 - 2003
  • EComStation 1.2 - 2004 ( revision: eComStation 1.2R - 2006)
  • EComStation 2.0 - 2010
  • EComStation 2.1 - 2011