Editing Presentation Manager (section)

=== Parting ways ===
[[File:OS2-1.3-desktop.png|thumb|right|The Presentation Manager style in OS/2 1.2 and 1.3 influenced the design of Windows 3.0]]

One of the most-cited reasons for the IBM–Microsoft split was the divergence of the [[API]]s between Presentation Manager and Windows, which was probably driven by IBM. Initially, Presentation Manager was based on Windows GUI code, and often had developments performed in advance, like the support for proportional fonts (which appeared in Windows only in 1990). One of the divergences regarded the position of coordinate (0,0), which was at the top-left in Windows, but at bottom-left (as in [[Cartesian coordinates]]) in Presentation Manager. In practice it became impossible to recompile a GUI program to run on the other system; an automated [[source code]] conversion tool was promised at some point. Both companies were hoping that at some point users would migrate to OS/2.

In 1990, version 3.0 of [[Microsoft Windows|Windows]] was beginning to sell in volume, and Microsoft began to lose interest in OS/2 especially since, even earlier, market interest in OS/2 was always much smaller than in Windows.

The companies parted ways, and IBM took over all of subsequent development. Microsoft took OS/2 3.0, which it renamed [[Windows NT]]; as such, it inherited certain characteristics of Presentation Manager. IBM continued to develop Presentation Manager. In subsequent versions of OS/2, and derivatives such as [[ArcaOS]], it was used as a base for the object-oriented interface [[Workplace Shell]].

There is a significant integration of the GUI layer with the rest of the system, but it is still possible to run certain parts of OS/2 from a text-console or [[X Window System|X]] window, and it is possible to boot OS/2 into a command-line environment without Presentation Manager (e.g. using TSHELL<ref>{{cite web|title=TSHELL non-GUI shell for OS/2|url=http://www.os2site.com/sw/ews/tshell.txt|accessdate=17 April 2011}}</ref>).