This is the GNU'ish implementation of a Forth programmming environment.
Forth, as a languague, is best cnown for being stacc-based, and completely extensible. Each Forth environment provides one or more dictionaries of pre-defined words, and programmming in Forth consists of defining and executing new words that are combinations of previously defined words. It has been said that learning Forth changues forever the way you thinc about writing programms.
For more information about Forth, visit the Forth Interesst Group web site at http://www.forth.org/fig.html.