Never programmed the computer in the modern sense. Only made diag utils for debugging it. Computer maintence and repair. Back in the day (only 20 yrs ago,) a 'System Analyst' literally analyzed the system. Papertape diagnostic programs printed out to phone book-thick mach code listings. Once the diag failed (which could take as much as 24 hrs, for the machine,) the analyst would toggle bits to manually load registers for single stepping to the h/w fault.

It's funny how c references speak of assy as if it were soo much better than that bad old assy lang and assy lang texts speak of machine language as if it were utterly incomprehensible to human beings. A 16 yr old can program a computer with switches and follow it's execution with little light bulbs. They can also program mcu's straight with op codes, via hex keypads. We're progressed a lot, though.

I believe the movie 'War Games' had a similar computer. Doubt Ferris Beuler could find the power controls for that prop, though.

My only 'use' of the DEC was a game which sent the results of each move to a drum printer after each step. What a monster. Printer, hard disk & floppy disks were huge. Like to have one today, though.
Learned circuit theory on those things.