At the time of writing, recent Tcl/Tk versions are: 7.4/4.0, 7.5/4.1, 7.6/4.2, and 8.0/8.0. There is also a version 8.1 in alpha testing. Versions 7.4/4.0 are the earliest versions that will make lots of sense with this book.

This book is written as if you are using Tcl/Tk versions 8.0/8.0. In a few places, versions 7.6/4.2 or 8.1/8.1 are mentioned.

Tcl/Tk 8.0/8.0 have significant improvements over earlier versions. Lists are handled in a much more efficient manner. A bytecode compiler makes repetitive code much more efficient. Some support for modular scripts is now available. Any one of these improvements would be reason enough to upgrade.

All of this book's examples and exercises have been tested on a Unix and a Windows platform.