For a solid working knowledge of Tcl, study Chapters 1—8. After that continue with Chapter 9 or skip to Chapter 11. When you have finished Chapter 19, you will have a solid working knowledge of Tk. You can add on the other topics as you need them.

In many chapters, there are sections which add no new facts about Tcl/Tk. These sections are useful because they provide examples that help you to develop a style for programming in Tcl/Tk that fits the language. However, they can be skipped on first reading. You can recognize these sections because their names are italicized.

The book is written for looking things up but do not expect all things to be present. Use your on-line manual if you do not see what you need in the book. Look for additional commands and look for additional ways of using commands that are in the book. There are two reasons you must do this: First, I have omitted some things to prevent the book from becoming deadly dull. Second, Tcl/Tk is constantly changing.

Here and there in the book, are script boxes which contain example Tcl or Tk scripts. For your convenience, the scripts in these boxes are also available in downloadable form. You can find them from this book's home page. The names of the downloadable files are the same as the names of the corresponding boxed scripts. The names, for example, "S4.5a" and "S10.7b," are chosen to identify the sections in which the script boxes are found – the final letter of a name differentiates between multiple script boxes in the same section.

The same home page indexes scripts which solve exercises. Although all exercises are solved in this book, only some solutions are also available at the Web site. Example names for on-line exercise scripts are "ES5.8c" and "ES24.4bW." Strip these names of the capital letters and you have the exercise that the script solves. The additional "W" at the end of "ES24.4bW" indicates that this "script" is a C program that has been prepared for compilation on a Windows system.

All exercise numbers and script numbers end with lowercase letters. Remove this lowercase letter and you have the section where the exercise or script may be found.

Index entries are to just one place in the text. When other places in the text provide important additional information, there are cross references.

Conventions for Procedures

Here is a pattern that shows how a Tcl procedure is invoked:

PROC_NAME ARG1 ARG2 ... ARGn 

Each of ARG1, ARG2, and so on, must match up with a variable found in the definition of the procedure, for example,

proc PROC_NAME {VAR1 VAR2 ... VARn}  { ... }

This kind of matching is done in almost all programming languages, but the terms to describe it are not universal. In this book each of ARG1, ARG2, and so on, is called an argument and each of the corresponding variables, VAR1, VAR2, and so on, is called a parameter.

Tcl procedures and commands always return a value. When that value is always an empty string, the description in this book is not likely to mention it.