Presentation Manager
| Company type | Software component |
|---|---|
| Industry | Computer software |
| Founded | 1988 |
| Founder | IBM, Microsoft |
| Headquarters | United States |
| Products | Graphical user interface for OS/2 |
Presentation Manager (PM) represents the graphical user interface (GUI) introduced jointly by IBM and Microsoft within version 1.1 of their operating system OS/2 during the late months of 1988.
History
The inception of a graphic user interface (GUI) by Microsoft began in 1981, leading to IBM's involvement in the project. Between 1987 and 1988, Presentation Manager (PM; internally known as Winthorn) was collaboratively created by Microsoft and IBM's Hursley Laboratory, combining elements from Microsoft Windows and IBM’s mainframe graphical environment (GDDM). Although PM shared a message-driven architecture akin to Windows, featuring comparable user interactions and application frameworks, maintaining source compatibility with Windows was not prioritized. For Microsoft, developing PM provided an opportunity to rectify architectural shortcomings found in Windows. Both corporations aimed to keep PM and Windows 2.0 closely synchronized.
Among the principal technical distinctions was the coordinate origin: Windows utilized a top-left corner starting point (0,0), whereas PM adopted a bottom-left origin. Both platforms employed Device Contexts (DC) for rendering graphics; however, PM introduced an additional abstraction layer termed Presentation Space (PS). The Graphics Programming Interface (GPI) within OS/2 offered enhanced drawing capabilities, some of which were later integrated into Windows NT. The programming paradigm in OS/2 was regarded as more refined, doing away with the necessity for explicit window procedure exports, WinMain entry points, and non-standard function prologues and epilogues.
Separation
One critical element precipitating the IBM–Microsoft division was the increasing divergence between Presentation Manager’s and Windows’ APIs, a shift largely influenced by IBM’s direction. Initially, Presentation Manager leveraged Windows GUI code but incorporated innovations such as proportional font support earlier than Windows did (Windows introduced this feature in 1990). A significant contrast lay in their coordinate systems: Windows used a top-left origin, while Presentation Manager’s coordinate system began at the bottom-left, complicating cross-platform recompilation despite promises of automated conversion utilities. Both companies expected users to transition toward OS/2.
By 1990, with Windows 3.0 achieving substantial market success, Microsoft's enthusiasm for OS/2 diminished due to its comparatively limited adoption. This led to a formal split: IBM assumed exclusive responsibility for developing OS/2 and Presentation Manager, whereas Microsoft adapted OS/2 version 3.0 into Windows NT, incorporating select aspects of Presentation Manager. IBM persisted in advancing Presentation Manager technology, which served as the foundation for the object-oriented Workplace Shell interface found in subsequent OS/2 releases and derivatives such as ArcaOS.
Although the GUI layer was tightly integrated with the operating system, OS/2 components could operate independently from a text console or within an X session. Furthermore, it is possible to boot OS/2 into a command-line mode without launching Presentation Manager—for instance, by using TSHELL.
Presentation Manager on Unix
During the late 1980s, a collaboration between Hewlett-Packard and Microsoft focused on porting Presentation Manager to Unix platforms utilizing X11. This initiative yielded two main parts: CXI (Common X Interface), encompassing a toolkit, window manager, and style guidelines; alongside PM/X, an implementation of the Presentation Manager API tailored for Unix environments. Both components were proposed to the Open Software Foundation as contenders for establishing a new standard Unix user interface, which eventually developed into Motif. The OSF ultimately endorsed CXI but selected Digital Equipment Corporation's XUI API over PM/X.
Following Motif's release, Microsoft and HP continued refining PM/X. Microsoft incorporated this work into a collaborative plan with SCO aimed at unifying user interfaces across OS/2 and SCO’s Unix offerings; however, this project was ultimately discontinued.
Technical details
PM complies with the interface guidelines established by Common User Access and incorporates mouse chording functionality to facilitate rapid text copying and pasting.
One significant obstacle involved the single input queue limitation, which could cause the entire interface to become unresponsive if an application stopped responding. Windows NT tackled this problem by displaying such applications as inactive blocks, subsequently enabling users to move or conceal them. In contrast, OS/2 addressed the issue through a FixPack update that implemented a timer mechanism to identify applications that were not responding.