Interval Timer:
Timer interruption is a technique that is closely related to preemption. When a process gets the CPU, a timer may be set to a specified interval. If the process is still using the CPU at the end of the interval, then it is preempted. Both timer interruption and preemption force a process to yield the CPU before its CPU burst is complete.
However, it is helpful to distinguish timer interruption from preemption caused by higher priority processes becoming ready for two reasons:
Timer interruption is a function of the particular process's own behavior. It is independent of the rest of the system.
Almost all multi-programmed operating systems use some form of timer to prevent a process from tying up the system forever. But preemption for a higher priority process is a feature that may or may not be included in a given operating system.
