I think it was something to do with one of the keyboard keys with an LED if I recall correctly, so possibly caps/numlock. Edit: seems I'm misremembering, just

I think it was something to do with one of the keyboard keys with an LED if I recall correctly, so possibly caps/numlock. Edit: seems I'm misremembering, just read - https://www.reddit.com/r/programmerchat/comments/3aknvw/prison_scene_in_cryptonomicon/ https://www.reddit.com/r/programmerchat/comments/3aknvw/pris... the LED was to output data, but they used another key to tap code