To carry out operations on the widget, you define a set of procedures called methods (to use common object-oriented terminology). Each method can be declared as public or private. Public methods can be called by the application programmer. For example, if the TixArrowButton class supports the public methods invoke and invert, the application programmer can issue the commands to call these method for the widget instance .up.
In contrast, Private methods are of interests only to widget writers and cannot be called by application programmers.