The Desktop (which also is an object), the objects that appear on the Desktop, and the underlying code supporting these objects constitute the OS/2 Workplace Shell, the default OS/2 user interface. Likewise, methods in the Workplace Shell are methods that were implemented for the creation of the Desktop object and its objects. This chapter describes Workplace Shell classes and characteristic behaviors of Workplace Shell objects. Because Workplace Shell objects are built using the IBM System Object Model (SOM), the OS/2 Workplace Shell Programming Interface requires a knowledge of SOM. It assumes a knowledge of object-oriented programming and design concepts, as well as SOM.