Privileged Instructions
These instructions (NOOP excepted) should be used only by the Operating System. The designation "privileged" is purely symbolic; there is no hardware protection to prevent their use by any application.
| 000000 | NOOP | No operation |
| 000001 | HALT | (requires manual resumption from Control Panel) |
| 000002 | MASK | Never used (Hangover from Mk 2?) |
| 000003 | Acknowledge Interrupt | Loads B-Register with highest priority interrupting Device Code |
| 000004 | Interrupt ON | Enables interrupts after completion of the immediately following instruction |
| 000005 | Interrupt OFF | Disables interrupts |
| 000006 | Skip if Interrupt ON | Tests interrupt state |
| 000007 | Skip if Interrupt OFF | Tests interrupt state |
| 000010 | Skip if MAINS OFF | Tests and clears Mains Off interrupt |
| 000011 | Skip if MAINS ON | Tests and clears Mains On interrupt |
| 000012 | Skip if PARITY | Tests and clears Parity interrupt |
| 000013 | Skip if PROTECTION | Never used |
| 000014 | Skip if BOUNDARY | Never used |
| 000015 | Skip if MA=SW | Tests and clears MA=SW interrupt |
| 000016 | Skip if CONTINUOUS INTERRUPT | Tests and clear Continuous Interrupt |
| 000017 | Input/Output RESET | (allow 1 second for devices to react) |