The conceptual model upon which a Presentation Manager application is based differs somewhat from "conventional" application models. The components of a conventional application communicate with one another via function calls and pass information in the form of parameters. The components of a Presentation Manager application are called windows, and communicate using messages which are transmitted between windows by Presentation Manager on the application's behalf.
This section will examine the conceptual application model implemented by Presentation Manager. The intent of this section is to provide the reader with an introduction only. A more detailed examination of the application model from a programmer's viewpoint is given in OS/2 Version 2.0 - Volume 4: Application Development.