ttable is a little program that prints truth tables. It runs from the command line under Unix and has not been tested elsewhere.
TkGate is a event driven digital circuit simulator with a tcl/tk-based graphical editor. [snip] The distribution comes with a number of tutorial and example circuits which can be loaded through the "Help" menu. The example circuits include a simple CPU, programmed to run the Animals game. [snip] TkGate is free software provided with source code under the Gnu Public License.There exists at least a Debian binary package for TkGate.