original: design philosophies two basic designs exist : event-driven -lrb- priority scheduling -rrb- designs switch tasks only when an event of higher priority needs service , called pre-emptive priority .
simplifications: pre-emptive priority is when regular work is done until a higher priority job comes in . there are two basic philosophies , or schools of thought , for design . priority scheduling is event-driven and pre-emptive priority is driven by need . event-driven designs switch tasks only when an event of higher priority needs service . philosophy basics are designed as two : event-driven : which tasks only when an event of higher priority needs service , called pre-emptive priority design philosophies . two basic designs exist : event-driven -lrb- priority scheduling -rrb- designs exchange tasks only when a more important event needs to be taken care of -lrb- called pre-emptive priority -rrb- . of the two basic design philosophies that exist , one is event-driven , and the other designs with higher priority needs service , which are called pre-emptive priority . two basic design principles exist : priority scheduling designs switch tasks when a more important event needs service . design philosophies two basic designs exist : event-driven -lrb- priority scheduling -rrb- designs switch tasks only when an event of higher priority needs service , called pre-emptive priority .