IPS (Interpreter for Process Structures) is a somewhat Forth-like language developed in the 1970s by Dr Karl Meinzer, mainly aimed at small computer systems that control equipment. It has been used for the on-board computer on several AMSAT (Amateur Radio) spacecraft (AO-10, AO-13 and AO-40), and is also planned to be used on future AMSAT spacecraft. More information about IPS is available at http://www.jrmiller.online/products/ipsbk.html and an archived copy of http://www.amsat.org/amsat/sats/ao40/ips.html.
For experimenting, testing and debugging, it can also be handy to run IPS on desktop systems. Available here is a package to run IPS on Linux (and other Unix-like) systems: ips-02.tgz.
Here's a screenshot of IPS running in an xterm, with the 'bigclock' and AO40 tracking
programs loaded: