n The selection function: determines which process in
the ready queue is selected next for execution
n The decision mode: specifies the instants in time at
which the selection function is exercised
u Nonpreemptive
F Once a process is in the running state, it will
continue until it terminates or blocks itself for I/O
u Preemptive
F Currently running process may be interrupted and
moved to the Ready state by the OS
F Allows for better service since any one process
cannot monopolize the processor for very long