An AST is an "asynchronous system trap",
otherwise known as an interrupt
routine.
Rob's absolutely right about what the acronym means, but I always found
the idea of an "asynchronous trap" to be an oxymoron. When I was in school,
"traps" were synchronous with instruction execution, and "interrupts"
were
asynchronous. It should be a "SST', not an "AST". It was always one
of my
pet peeves about VMS J
Bob