IEEE Bushy Tree

OS/2 1.1 was a major release of OS/2 which appeared in late 1988. Presentation Manager, the main GUI was first implemented in this version. The GUI takes a strong resemblance to Windows 2.x and IBM's own mainframe graphical system, GDDM. The program paradigm also strongly resembles Windows. There were noted differences between both systems:

  • A different coordinate system. While in Windows the 0,0 coordinate was located in the upper left corner, in Presentation Manager, it was in the lower left corner.
  • In Windows all drawing operations went to the Device Context. Presentation Manager also used DCs but there was an added level of abstraction called Presentation Space (PS).
  • OS/2 had much more powerful drawing functions in its Graphics Programming Interface which was borrowed from GDDM. Some of the GPI concepts were incorporated into later versions of Windows
  • The OS/2 programming model was much cleaner. There was no need to explicitly export the window procedure, no WinMain, no nonstandard function prologs and epilogs.

IBM had written support on how programmers from Microsoft can port code and programs from Windows to OS/2. However, it's said that a lack of organization between Microsoft and IBM, and a lack of a clear strategy resulted in late releases of programs (such as Word 5.x and Excel) which happened to work in Microsoft's favor. However, a lot of the languages developed by Microsoft, such as assembler, Pascal, and COBOL were fully supported by OS/2, as were Microsoft's networking efforts (before the release of NT).

"Large" FAT support (a theoretical limit of 2 gigabytes) was added in version 1.1.

Compared with the then current version of Windows and Mac OS, OS/2 1.1 was technically superior as Mac and Windows had yet to introduce preemptive multitasking, multithreading or virtual memory. However, OS/2 1.1 had no graphics support beyond CGA, EGA and VGA, and had minimal printer support. Major business applications were scarce for this OS, but applications such as Microsoft Excel were proven to be powerful.

In late 1989, IBM and Microsoft released OS/2 version 1.2. This was a highly important event in OS/2 history because version 1.2 implemented most features promised for OS/2 before it even appeared. The most important of these being the first Installable File System, the High Performance File System (HPFS), designed by Gordon Letwin. A version of HPFS would later be included with the Microsoft LAN Manager.

OS/2 1.2 features a new look and feel, which was carried over into OS/2 1.3. Of note, is how the Presentation Manager resembled and felt like Windows 3.0, which was released a few months later. Many applications written for OS/2 1.2 were backwards compatible with OS/2 1.3, but were incompatible with OS/2 1.1. There were other major differences between OS/2 1.2 and Windows 3.0:

  • Windows 3.0 ran on top of DOS
  • Windows 3.0 carried a wide variety of drivers and applets, compared to OS/2 1.2.
  • OS/2 1.2 appeared to be geared towards businesses, while Windows 3.0 gained a wider acceptance among end users.[1]

In December of 1990, IBM released OS/2 version 1.3 after a split with Microsoft. The appearance was similar to that of OS/2 1.2, but with added optimizations and enhancements. It is important to note that Microsoft had released it's version of OS/2 1.3 along with IBM. Microsoft's version included different drivers, along with some SCSI drivers (This version was geared as Microsoft's server OS, before NT) IBM's EE version of OS/2 1.3 contained Communications Manager, Database Manager (a predecessor of DB2/2) and LAN Requester (This version was geared specifically towards corporations).

OS/2 1.3 carried the following features:

  • Preemptive multitasking
  • Multithreading
  • Fully protected memory
  • No 640K memory limit for OS/2 apps
  • Theoretical virtual memory of up to 1GB
  • Windowed and fullscreen OS/2 sessions
  • Support for REXX

Because it was designed to run on a 286 processor, OS/2 1.3 carried the following limitations:

  • Support for only 16MB of physical memory
  • Support for 16-bit apps only
  • Only one single fullscreen DOS session with not very good compatibility[2]
OS/2 Warp 4.0 Branch
Preceded by
IBM OS/2 1.0
IBM OS/2 1.x Followed by
IBM OS/2 2.x
Xerox Star (8010) branch
Influenced by
Xerox Star (8010)
IBM OS/2 1.x Influenced
Windows XP Branch
Influenced by
IBM OS/2 1.x Influenced
Mac OS X Branch
Influenced by
IBM OS/2 1.x Influenced