There are different implementations of course, but the most prevalent is this one:

http://en.wikipedia.org/wiki/Elevator#The_elevator_algorithm

Since in actual buildings the ground floor is usually used more frequently than others, there are also a fair amount of implementations which let the elevator return to the ground floor after a certain time of inactivity.

(On a side note, there is a telling that Donald Knuth once spent a day in an elevator just to be absolutely sure that he would describe the elevator algorithm correctly, but I can't find a reference for that.)

There are different implementations of course, but the most prevalent is this one:

https://en.wikipedia.org/wiki/Elevator#Elevator_algorithm

Since in actual buildings the ground floor is usually used more frequently than others, there are also a fair amount of implementations which let the elevator return to the ground floor after a certain time of inactivity.

(On a side note, there is a telling that Donald Knuth once spent a day in an elevator just to be absolutely sure that he would describe the elevator algorithm correctly, but I can't find a reference for that.)