xhello is a simple hello world program using Label widget.

xgoodbye is like hello with callback on Command widget

xfarewell is like xgoodbye but adds actions to Command instead of using
callbacks - click invokes a dialog confirming exit - Shift click
exits without the confirmation.  Also demonstrates setting and 
getting resources.

xclickcount.c and xwhichbutton.c are not described in the book.
They are very similar to xfarewell.  xwhichbutton adds action so
that a Command widget executes one of three different action
depending on which button is pressed (this user interface convention
is not necessarily recommended).  \f(CWxclickcount\fP resets
the label displayed in a Command widget to indicate the number of
times the Command is clicked.  xclickcount demonstrates getting
a user-supplied resource so that the program can change a label without
erasing the user-supplied part of it.
