There are three types of process scheduler.
1. Long Term or job scheduler It bring the new process to the ‘Ready State’. It controls Degree of Multi-programming, i.e., number of process present in ready state at any point of time.
2. Short term ot CPU scheduler: It is responsible for selecting one process from ready state for scheduling it on the running state. Note: Short term scheduler only selects the process to schedule it doesn’t load the process on running.
Dispatcher is responsible for loading the selected process by Short Term scheduler on the CPU (Ready to Running State) Context switching is done by dispatcher only. A dispatcher does following:
1) Switching context.
2) Switching to user mode.
3) Jumping to the proper location in the newly loaded program.
3. Medium term scheduler It is responsible for suspending and resuming the process. It mainly does swapping (moving processes from main memory to disk and vice versa).
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