OS/2 was intended as a protected mode successor of PC-DOS. Notably, basic system calls were modeled after MS-DOS calls; their names even started with "Dos" and it was possible to create "Family Mode" applications: text mode applications that could work on both systems. Because of this heritage, OS/2 is like Windows in many ways, but it also shares similarities with Unix and Xenix. IBM made a deal with Commodore to license the Amiga technology IBM OS/2 Warp History. . for OS/2 2.0 and above, and OS/2 still has some Amiga GUI code in Workplace Shell as a result as well as third party code not written by IBM.
OS/2 is also remembered for being one of the first major operating system to have its own advocacy group. Team OS/2 was a grassroots, ad-hoc organization of volunteers, who promoted and supported the operating system and applications designed for it.
OS/2 1.0 was announced in April 1987 and released in December as a text mode-only OS. However, it featured a rich API for controlling the video display (VIO) and handling keyboard and mouse events so that programmers writing for protected-mode no longer had to call the BIOS or access hardware directly. In addition, development tools included a subset of the video and keyboard APIs as linkable libraries so that family mode programs were able to run under MS-DOS. A task-switcher named Program Selector was available through the Ctrl-Esc hotkey combination, allowing the user to select among multitasked text-mode sessions (or screen groups; each could run multiple programs).
The promised GUI, Presentation Manager, was introduced with OS/2 1.1 in October, 1988. It had an almost identical user interface to Windows 2.1.
The Extended Edition of 1.1 sold only through IBM sales channels introduced distributed database support to IBM database systems and SNA communications support to IBM mainframe networks.
Version 1.2 introduced Installable Filesystems and notably the HPFS filesystem. HPFS provided a number of improvements over the older FAT filesystem, including long filenames and a form of alternate data streams called Extended Attributes. In addition, extended attributes were also added to the FAT filesystem.
OS/2 and Windows-related books of the late 1980s acknowledged the existence of both systems and promoted OS/2 as the system for the future.
Given these issues, Microsoft started to work in parallel on a version of Windows which was more future-oriented and more portable. The hiring of Dave Cutler, former VMS architect, in 1988 created an immediate competition with the OS/2 team, as Cutler did not think much of the OS/2 technology and wanted to build on his work at Digital rather than creating a "DOS plus". His "NT OS/2," was a completely new architecture.
IBM grew concerned about the delays in development of OS/2 2.0 and the diversion of IBM funds earmarked for OS/2 development towards Windows. Initially, the companies agreed that IBM would take over maintenance of OS/2 1.0 and development of OS/2 2.0, while Microsoft would continue development of OS/2 3.0. In the end, Microsoft decided to recast NT OS/2 3.0 as Windows NT, leaving all future OS/2 development to IBM. From a business perspective, it was logical to concentrate on a consumer line of operating systems based on DOS and Windows, and to prepare a new high-end system in such a way as to keep good compatibility with existing Windows applications. While waiting for this new high-end system to develop, Microsoft would still receive licensing money from Xenix and OS/2 sales. Windows NT's OS/2 heritage can be seen in its initial support for the HPFS filesystem, text mode OS/2 1.x applications, and OS/2 LAN Manager network support. Some early NT materials even included OS/2 copyright notices embedded in the software. One example of NT OS/2 1.x support is in the WIN2K resource kit. OS/2 support also includes Presentation Manager support with the addition of the Windows NT Add-On Subsystem for Presentation Manager.
OS/2 2.0 was, unlike its predecessor, a hybrid 16-bit/32-bit operating system although performance did not notably degrade on the Pentium Pro, an Intel CPU renowned for poor 16-bit performance at the time. The graphics subsystem (Gre) and multimedia (MMPM/2) were updated in a servicepack (and bundled into OS/2 2.1), Warp 3 brought about a fully 32-bit Windowing system, whilst Warp 4 introduced the object-oriented 32-bit GRADD display driver model.
Like most 32-bit environments, OS/2 could however not run protected-mode DOS programs using the older VCPI interface, unlike the Standard mode of Windows 3.1; it only supported programs written according to DPMI. (Microsoft discouraged the use of VCPI under Windows 3.1, however, due to performance degradation.)
Unlike Windows NT, OS/2 also always gave DOS programs the possibility of masking real hardware interrupts, so any DOS program could deadlock (crash) the machine this way. OS/2 could however use a hardware watchdog on selected machines (notably IBM machines) to break out of such a deadlock. Later, release 3.0 leveraged the enhancements of newer Intel 486 and Intel Pentium processors—the Virtual Interrupt Flag—to solve this problem.
Because OS/2 only ran the user-mode system components of Windows, it was not compatible with Windows device drivers (VxDs) and applications needing them.
Multiple Windows applications ran in a single Windows process, just as they would under native Windows. To achieve true isolation between Windows 3.x programs, OS/2 could run multiple copies of Windows in parallel. This approach required considerable system resources, especially memory. It was possible to use DDE between OS/2 and Windows applications, and OLE between Windows applications only.
OS/2 version 3.0, released in 1994, was labelled as "OS/2 Warp" to highlight the new performance benefits, and generally to freshen the product image. "Warp" had originally been the internal IBM name for the release: IBM claimed that it had used Star Trek terms as internal names for past OS/2 releases, and that this one seemed appropriate for external use as well.
OS/2 Warp offered a host of benefits over OS/2 2.1, notably broader hardware support, greater multimedia capabilities, Internet-compatible networking, and it included a basic office application suite known as IBM Works. It was released in two versions: the less expensive "Red Spine" and the more expensive "Blue Spine" (named for the color of their boxes). "Red Spine" was designed to support Microsoft Windows applications by finding and using Windows already installed on the computer's hard drive. "Blue Spine" included Windows support in its own installation, and so could support Windows applications without a Windows installation. As most computers were sold with Microsoft Windows pre-installed, "Red Spine" was the far more popular product. OS/2 Warp Connect, which had full LAN client support built-in, followed in mid-1995. Warp Connect only came with Windows support built in as well and was nicknamed "Grape."
In 1996, Warp 4 added Java and speech recognition software. IBM also released server editions of Warp 3 and Warp 4 which bundled IBM's LAN Server product directly into the operating system installation. A personal version of Lotus Notes was also included, with a number of template databases for contact management, brainstorming, and so forth. The UK-distributed free demo CD-ROM of OS/2 Warp essentially contained the entire OS and was easily, even accidentally, cracked, meaning that even people who liked it didn't have to buy it. This was seen as a backdoor tactic to increase the number of OS/2 users, in the belief that this would increase sales and demand for third-party applications, and thus strengthen OS/2's desktop numbers. This suggestion was bolstered by the fact that this demo version had replaced another which was not so easily cracked, but which had been released with trial versions of various applications. In 2000 the July edition of Australian Personal Computer magazine bundled software CD-ROMs, included a full version of Warp 4 that required no activation and was essentially a free release.
IBM also released a version of OS/2 that ran on its PowerPC workstations, and promised to produce low-cost PC style machines with the PowerPC processor. However, the PowerPC version of OS/2 was dropped less than a month after its release, and plans for supporting machines were scuttled. Such moves were seen in the industry as indicative of IBM's lack of long-term commitment to the operating system. Ironically, Microsoft Windows NT provided support for PowerPC — a chip co-developed and promoted by IBM — for over 5 years.
Warp 4 was the last widely distributed version of OS/2, and IBM soon announced the end of marketing the operating system to individual users.
Although IBM began indicating shortly after the release of Warp 4 that OS/2 would eventually be withdrawn, the company did not end support until 2006-12-31. Sales of OS/2 stopped on 2005-12-23. 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 stable version is 1.2, released in 2004. Version 2.0 was due for release early in 2007, but release candidate 4 for version 2.0 was not released until December 2007.
IBM is still delivering defect support for a fee. 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 migration to a different operating system, suggesting Linux as an alternative.
A side effect of this is that it is difficult to run OS/2 inside of the popular VMware software product. A beta of VMWare Workstation 2.0 released in January 2000 was the first hypervisor which could run OS/2 at all. Later, the company decided to drop official OS/2 support, presumably because it would require serious work that cannot be economically justified. It is still possible to boot OS/2 by setting guestOS = "os2experimental" in the .vmx file of the VM (checked with VMware Workstation 3.0 and 5.5), but trying to run different versions of OS/2 leads to frustrating problems most of the time. Specifically, one can run OS/2 Warp 4 at Fixpack 5, but installing later Fixpacks will make the virtual machine unusable. eComStation 1.2 and 2.0 beta 4 will not install. Versions 1.x will crash immediately with a "TRAP 0000". Versions 2.x are too ancient to recognize the simulated IDE CD-ROM, do not recognize the virtual SCSI hardware and can crash with "TRAP 000C" after some operations.
Version 3.0 (Red) and Version 4.0 (Warp 4) seems to work fine under VMWare Server 1.04, however the 'guestOS = "os2experimental"' will flash an error and change the vmx file to guestOS = "other". This seems to work just fine for both of these versions.
The lack of official VMware support for running OS/2 created the opportunity for a new virtualization company. A large German bank needed a way to use OS/2 on newer hardware that OS/2 did not support. As virtualization software is an easy way around this, it desired to run OS/2 under a hypervisor. Once it was determined that VMware was not a possibility, it hired some Russian software developers to write a host-based hypervisor that would officially support OS/2. Thus the Parallels, Inc. company and their Parallels Workstation was born.
Microsoft continues to support OS/2 as a hosted operating system in its Virtual PC product. OS/2 and eComStation can both be installed in Microsoft VirtualPC (checked with VPC 2004) although a virtual machine built in VPC 2004 would not run in VPC 2007.
VirtualBox from Sun Microsystems currently supports OS/2 Warp 3, 4 and 4.5 as well as EComStation as guests. Innotek (now part of Sun) also developed the “additions” code in both Virtual PC and Virtual Server which greatly improves host-guest OS interactions in OS/2.
QEMU and Bochs also support running OS/2 as they're full x86 system emulators and not virtualization software, and thus emulates the entire x86 architecture instead of relying on the host CPU, essentially allowing OS/2 unrestricted access to Ring 2, albeit an emulated one.
Diebold Incorporated initially shipped XP Embedded Edition exclusively but following extensive pressure from customer Banks to support a common OS had them switch to support XP Professional to match their primary competitor NCR Corporation.
Version 2.0 had such a long design cycle that its design started while OS/2 1.1 was still under development, and thus, portions of it were developed in conjunction with Microsoft, even though Microsoft never released a branded version of 2.0 (although they did release a beta in their name). IBM's contribution to versions 1.2 and earlier mostly resides in the GUI components; however, bug fixes and substantial performance changes to the entire system in 1.3 were made by IBM , and much more of the overall system (including the kernel) for 2.0 was developed by IBM.
The aborted PowerPC port did not involve Microsoft at all, and has been proposed as the basis for an open-source 64-bit version of OS/2.
Still, the community has suggested that, even if only the IBM portion of it is made open, the missing parts could be written by the same community to form a next-generation version of the OS. Code could perhaps be integrated from the Wine or ReactOS projects. Many developers believe that these missing parts include many of the legacy 16-bit components not revised since OS/2 1.x, and are exactly the parts that should be rewritten anyway. There is an ongoing petition to open parts of the OS arranged by OS2World.com.
With the possibility of an open-source future for OS/2, the OS may be given a new lease of life. IBM's current and heavy involvement with several open source projects indicate that opening parts of OS/2 will not be difficult for the company. But until then, OS/2's future remains in limbo.
Hardware vendors were reluctant to support device drivers for alternative operating systems including OS/2 and Linux, leaving users with few choices from a select few vendors. To relieve this issue for video cards, IBM licensed a reduced version of the Scitech display drivers, allowing users to choose from a wide selection of cards supported through Scitech's modular driver design.
WPS 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 radical advancement in application development with compound document technology called OpenDoc, which was developed with Apple. OpenDoc proved interesting as a technology, but was not widely used or accepted by users or developers. OpenDoc is also no longer being developed.
The multimedia capabilities of OS/2 are accessible through Media Control Interface commands. The last update (bundled with the IBM version of Netscape Navigator plugins) added support for MPEG files. Support for newer formats like PNG, progressive JPEG, DivX, Ogg, MP3 comes from third parties. Sometimes it is integrated with the multimedia system, but in other offers it comes as standalone applications.
During the next 10 years, millions of programmers and users will utilize this system. Bill Gates, November 1988 (in the Foreword to the Inside OS/2 book by Gordon Letwin, Microsoft's architect for OS/2).
This quotation could be compared with another one, by Dave Cutler and coming from his introduction to the Inside Windows NT book:
However, as "Inside Windows NT" says in chapter one, section 1.1, "An Operating System for the 1990s":