OK ... OK ... here are the answers:

They were ALL legitimate commands:

=========================================================

Which of the following were legitimate MPE commands, and
what do they do?

:SETLOCK        Set a file lockword.
:LOADER         Invoke the loader subsystem.
:CHART          Flowcharter.
:WAITOP         Wait for a reply message from the operator.
:SHOWCHARGES    Show resources used for chargebacks.
:USE            Use a user command dictionary.
:CEASE          Cease using a user command dictionary.
:LISTCOM        List the commands in a dictionary.
:BUILDCOM       Build a dictionary.
:ADDCOM         Add a command to the dictionary.
:PURGECOM       Purge the dictionary.
:TASK           Didn't you know MPE was a real-time tasking OS too?
:SHOWTASK       Show those real-time tasks.
:ABORTTASK      Abort it when it runs away with the CPU.
:LOADINT        Load an interrupt routine.
:UNLOADINT      Unload the interrupt routine.
:DISCONNECT     Suspend an online session with the intention of returning.