This directory and its descendants contain the sources and documentation for Tcl, an embeddable scripting language. The information here corresponds to release 8.0.5, which is the fifth patch update for Tcl 8.0. The compiler introduces many new C-level APIs, but the old APIs are still supported. See below for more details.
Binary releases are much easier to install than source releases.
Also, check in the FTP directory from which you retrieved the base distribution. Look in the FTP directory from which you retrieved this distribution to see if it has been updated with patches. Patch releases fix bugs without changing any features, so you should normally use the latest patch release for the version of Tcl that you want. Patch releases are available in two forms. A file like tcl8.0.5.tar.