Back in the dark ages ... the first program I wrote when I went from (ass embler) applications programming to system programming was a program to issue CP commands (via EXEC pgm=xxxxxxx,parm='cp-command") in JCL). Back then we didn't consider any sort of security necessary. (I don't know what class we ran our MVT guests. I hope it was class G.)
I remember puzzling over LRA (Load Real Address) and DIAG 8. Ah, the bad old days.
