Plot-10 was a callable library, correct.
Other commands could also be used to talk to this terminal directly,
in a different language, simpler. Plot-10 was meant to work with
whole ranges of Tek devices. I have good docs on a 4107 (probably
very similar) and can fish up info for you from there. At this escape
sequence level it was very much like a DEC VT125, (only faster,
sharper and more functional) if you've ever been there.
John A.