Differentiate between pre-emptive and non-pre-emptive scheduling.
Pre-emptive scheduling: in its approach, center processing unit can be taken away from a process if there is a require while in a non-pre-emptive approach if one time a process has been specified the CPU, the CPU can't be taken away from such process, unless the process leaves or completes the CPU for performing an Input and Output.
Pre-emptive scheduling is more helpful in high priority process that requires immediate response, for illustration in real time system. Whereas in non-preemptive systems, jobs are made to wait through longer jobs, but treatment of each process is fairer.