This CVS-hosted module, available from http://tcl.sf.net/ is intended primarily to demonstrate to C developers how to write a Tcl extension in C that can be dynamically loaded as well as how to structure the directories so that someone can use configure and make to build and install said extension. In coarser perspective, think of it as a lesson in how to use C functions from Tcl.
For more information, read about TEA and TEA2. [What's the exact URL at SF?] [The exact URL of what? SampleExtension? Modules don't really have an exact URL. You visit the release page and pick up whatever happens to be latest.]