Andy, I went through the TurboCNC (reminds me of Turbo Pascal

) and found this website:
http://www.seanet.com/~dmauch/
it uses frames so I can't direct link, but in the menu click on "secrets of CCNC", and scroll down a bit: there is a whole section explaining how the parallel port control works and a whole lot more useful information.
Thanks again Andy!
-Leav