Tcl is written in C. Tcl's source code is shipped with a library of C functions which extends those used to implement Tcl in ways that support extensions of Tcl. That in a nutshell is the C/C++ connection.

Although the level of C programming skill necessary to work your way through these four chapters is not very high, to get very much use from the material herein, you must be a C/C++ programmer or be willing to work at becoming one.

This is the chapter where you learn to apply your C/C++ compiler to making Tcl commands or math functions. The few exercises ask you to do this for a trivial new command. The point is for you to take the time to get things together so you can actually create a new Tcl command. Without this practice, subsequent chapters on how to implement new commands are useless.

• Data Types in Transition
• C Procedures that Run as Tcl/Tk Commands
• Naming Conventions
• Registering Commands
• Extending Tcl with the Recompile/Relink Method
• Extending Tcl with the Load Method
• Creating Math Functions
• Tk
• Solutions to Exercises