i was pretty simple with the commodore 64, just use peeks and pokes to the user port
There is peek and poke programs for the Amiga which let you set the printer port (and obviously anything else) so the Amiga didnt make things any harder.
(There was a nice piece in Amiga format about peeking and poking the Amiga's registers in a thing they did on the CIA chips, was well cool)
