What did computers without screens do?

Depends on what counts as a "screen". If any visible output counts, there isn't much - but I suspect you don't want to go that far. You can connect to it from other computers. I have six machines running right now with no screens on them (though four of them have the host-side hardware for a screen). You can talk to it with a terminal. If a video-display terminal counts as a screen, use a printing terminal. You can use whatever output it _does_ have. I had (I've since passed it along to someone who appreciated it more than I did) a PDP-8/f. It had a row of lights which functioned as an output device. Another machine I used in the past had a small LED display, something like one line of twenty characters (though that may count as a screen). I'm sure I've missed some options.... /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B