What is Tcl/Tk?

Tcl/Tk, as its title suggests, is actually two software packages: Tcl and Tk. Tcl, pronounced tickle, stands for tool command language and is a scripting language that provides a programming environment and programming facilities such as variables, loops, and procedures. It is designed to be easily extensible.

Tk, pronounced tee-kay, is just such an extension to Tcl which is a toolkit for windowing systems. In other words, Tk adds facilities to Tcl for creating and manipulating user interfaces based on windows and widgets within those windows.