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Reviewer: Wei-Ming Hu

Tcl (tool command language) is a language for writing scripts that control program execution. Tk is a Tcl extension that allows you to construct X Windows–based user interfaces. Since the author wrote both Tcl and Tk, this book is the definitive reference on the subject. The book is divided into four parts. The first part describes the Tcl language. It describes each of the features of Tcl and gives brief examples of how they can be used. Starting with variables and expressions, the book continues with control structure, procedures, string manipulations, and so on. By the end of this section, the reader should be able to write scripts within a Tcl-based interpreter. Part 2 is on writing Tk scripts. It starts by describing the X Windows widgets (scroll bars, buttons, menus, and so on) that Tk provides. It then talks about how to control the appearances of these widgets, how to associate handlers to events, how to get user selection input, and how to pass data across windows. It also includes a small application that uses Tk. Parts 3 and 4 describe how to embed Tcl and Tk in C programs. This allows you to, for example, implement new Tcl commands and create new Tk widgets. It is also how you can use Tcl and Tk as your application's command interface. The book covers such topics as how to pass data between your application and Tcl/Tk, how to build extensions, and the programming interfaces to some of the internal support routines used by Tcl. The last section of the book gives directions for obtaining the source code to Tcl and Tk. Overall, the book is a great reference. It is comprehensive: all the features of Tcl and Tk are described. The organization of the book, centered around language and toolkit constructs, also makes it easy to look things up. The short examples associated with each feature make the usage clear. The book definitely succeeds in giving the reader a good knowledge of all the pieces of Tcl and Tk. The book helps the reader get started with Tcl and Tk. By itself, however, it does not give the reader enough information to use the language and toolkit features for sophisticated applications. What is missing are design guidelines and hints. It is easy to fall into the trap of writing Tcl-based applications that are predominantly C applications. It is much harder to design your application to minimize the amount of C code that is required. The book does cover some design issues. For example, there is a chapter on the philosophy of using Tcl in C programs. More complete examples would have helped, however. The reader should definitely take advantage of the sample applications that are available on the Internet (and with the Tcl/Tk distribution).