6.1 Window Concepts and Operation

In PDP++ the hierarchy of objects provides the basis for most of the gui (Graphical User Interface) interaction. To access a sub-object of a class, the best place to start is with the gui window for the parent class instance and work your way down to the sub-object. The higher levels of the hierarchy have windows which are mapped to the screen when the object is created. These windowing objects inherit from the base class WinBase. When PDP++ starts up, only one of these classes has been created and thus there is only one window on the screen. The initial object is an instance of the class PDPRoot, and is the top of the PDP hierarchy.