Consider a real - time weapons control system aboard a fighter aircraft. Discuss which of the following events would be considered synchronous and which would be considered asynchronous to the real - time computing system.

(a) A 5-ms, externally generated clock interrupt.

(b) An illegal - instruction - code (trap) interrupt.

(c) A built - in - test memory failure.

(d) A discrete signal generated by the pilot pushing a button to fi re a missile.

(e) A discrete signal indicating “ low on fuel. ”