A date is given as the seed for the RNG, in a "horoscope"-like fashion.
After decompiling, it became clear that the commands to the plotter are 6 bit wide and are, in octal:
- 11 - pen up
- 12 - pen down
- 00-07, 30-37 - king-wise movements, knight-wise movements (as dealing with them is in an assembly block, it's not immediately obvious which is which, and what directions they correspond to)
I've produced the picture by replacing the pen movement routine with
if penDown then writeln(dx, dy, ' rlineto') else writeln(dx, dy, ' rmoveto');
and sending the result to GhostScript.
My question is, what plotter was accepting those commands? One likely target would be a Calcomp, probably Calcomp 565
but it could be another Calcomp model, or a Benson (those two brands were known to have been used with the BESM-6).
(The date used in the picture is the build date of the program which appears in the binary.)
Update: I've found that it was Calcomp 763 or 765 and a reference page, but I could not find an English-language reference manual for those devices.