In Tron (1982), this background character is moving a CAD digitizer puck over an image of the solar sailer, which is how the concept art for it would have been entered into graphics workstations at the time.

this is a really cool detail!

OG Tron was on another level. I think I remember from a behind-the-scenes extra on the DVD that they shot the in-computer scenes (90% of the movie) in black and white and had to colorize all the light lines on the programs’ outfits frame by frame by hand.