Part III introduces Tk, the toolkit for building graphical user interfaces. The Tcl command interface to Tk makes it quick and easy to build powerful user interfaces. Tk is portable and your user interface code can work unchanged on UNIX, Windows, and the Macintosh.
Chapter 21 describes the basic concepts of Tk and provides an overview of its facilities.
Chapter 22 illustrates Tk with three example programs including a browser for the examples from this book. These examples use facilities that are described in more detail in later chapters.