On Star Trek, you got it, it was pretty much a terminal based setup. They were kind of more like smart terminals, cause they had those cool little multi-colored memory sticks they would use for presentations and reviewing recordings and such. You could always hear Spock talking about the "ship's computer is working on <insert research here>." But I can't say much about the Battlestar Galactica computers. A picture of one would be good, yea.
Nathan
/edit Found a picture, but it doesn't look much like a PET. More like an IBM something or other. Reminds me most of that huge IBM terminal they used to use at the hospital back in the day(like 1999). The insurance company said use it so we used it. had lots of extra buttons like the one in the battlestar pic, too.
http://content.answers.com/main/content/wp/en/thumb/5/55/250px-Bgpromo1.jpg
Is this what you meant??