xbox1	simple box
xbox2	simple form
xbox3	invokes dialog, with text entry, not using XtCallbackExclusive
xbox4	simple box using static argument lists and callback lists
xbox5	invokes dialog, without text entry, using XtCallbackExclusive (callback list with PrepareDialog)

Ex3-6	Example 3-6 from book:  passing a number to a callback through client_data
Ex3-7	Example 3-7 from book:  passing a structure to a callback through client_data
