Presentation Manager
Sometimes abbreviated as PM, Presentation Manager is a GUI (graphical user interface) for the OS/2 operating system that was a joint effort between Microsoft and IBM. It was released in 1988 and shared many similarities with the desktop in Windows. In fact, the style of PM on OS/2 versions 1.2 and 1.3 significantly influenced the appearance of Windows 3.0.
Presentation Manager included many Windows-like features, such as the ability to run more than one application simultaneously in separate windows. It also had drag-and-drop functionality, a set of graphical user interface controls, and a framework for developing applications.
One significant difference between PM and Windows was the starting points for their respective coordinate systems. In Presentation Manager, the (0,0) coordinate was located in the lower-left corner, while in Windows, it was located in the upper-left corner.
The starting point difference made it impossible to recompile PM to run on another operating system. Along with IBM's strategy to compete with Microsoft Windows, that difference led to a divergence between the two GUIs. Despite its capabilities, such as utilizing proportional fonts, OS/2 never gained as much popularity as Windows in the consumer market.