This chapter covers the fundamentals of widgets based on the Xt Intrinsics. It discusses what a widget is, what makes up a widget, the basic widgets in the Xt Intrinsics, and a new concept called the windowless object (the OSF/Motif Gadget is an example of this). it is useful to point out the two types of programmers that exist in the Xt Intrinsic Domain: widget writers (WW) and client writers (CW). A widget writer cares how the widgets are structured. He or she is quite concerned about changes to the core elements of the widget. Some vendors snatched up the source for the Athena widgets and made "minor" changes. Those programmers who tried to write portable code would often find problems moving from machine to machine — especially when they had written new widgets that were subclasses of existing widgets.