Emptive

Mike Malone recalls how the shaving of his fiancée's head was more of an “emptive” strike, since her hair was already on its way out.

Emptive priority: The service to non-priority customer is stopped as soon as a priority customer arrives.

This situation can be dealt with either in an emptive or pre-emptive fashion. In an emptive system the new entry waits for the other to be completed before beginning. In a pre-emptive system the queue can stop the current entry half way through its execution to start the new one.