What HP OS could it be??

Ok HP experts out there One saturday my programming class in high school went on a field trip to Santa Clara University. We got to try out some of the minicomputers there. I asked the people who were with us if I could come back and use the computers any other time, they said "sure as long as you don't get in anyone's way", so for almost a year, in the dark morning hours I would go down and program in fortran.. using the card punches and seeing my output on the line printer. What OS was I running? Here's everything I remember: HP2100, Card Reader, Beehive CRT terminal, Line Printer, Flat-slip in horizontal cartridge disk drive/with fixed platter, Paper tape punch and reader, and a plotter The machine was in the engineering department of University of Santa Clara, in around 1976 Jobs were written in Algol or Fortran, and punched on cards. Job control cards had //somthing blah.... The boot loader was stored at (i think) 102077 (punch this in the switch register and hit run???) What was I using?