WHAT IS CPU SCHEDULING?
         
             Scheduling refers to the set of policies and mechanisms that an OS support for determining the order of execution of the pending jobs and processes.

WHAT ARE THE OBJECTIVE OF CPU SCHEDULING?

            1. Fairness:
                                 Makes sure each process get it's fair of CPU.
         
            2. Efficiency:
                                   Keep the CPU busy hundred percent so that efficiency is increased.

            3. Response time:
                                       Minimize the response time.
 
            4. Through put:
                                        Minimize the through put.

            5. CPU Utilization:
                                          The CPU utilization specially on the time shared system should be maximum.

WHAT IS  SCHEDULER?

             When more than one process is runable,the OS must decide which one to be run fast. The part of the OS concerned with the decision is called scheduler, and the algorithm it uses is called the scheduling algorithm.

TYPE OF SCHEDULER:

                  1. L.T.S (Long Term Scheduler)
                  2. M.T.S(Middle Term Scheduler)
                  3. S.T.S(Short Term Scheduler) 

1. L.T.S (Long Term Scheduler):
                                                       The long term scheduler is also called the job scheduler. This scheduler determines which jobs are admitted to the system for processing. It is also called admission scheduler, because it determines which job gains admission to the system.

                    In batch processing system more jobs are spooled to a mass storage device. The Long Term Scheduler select these job from job pools and loads these into memory for execution.

2. M.T.S(Middle Term Scheduler):
                                                                 many time we need to remove a process from the main memory as this process maybe in need of some input output operation. So such processes may be removed or suspended from the main memory to the hard disk. Letter on this process can be reloaded into memory and continued from from it was left earlier. This saving of the suspended process is said to be swaped out or rolled out and this swapping is done by medium term scheduler.

               It acts as the intermediate between LTS and STS.                                                    
                                       
3. S.T.S(Short Term Scheduler) :
                                                      This scheduler is sometime called CPU scheduling, or CPU scheduler. The short term scheduler selects among the job in memory, which are ready to execute and allocate the CPU to one of them. It's main objective is to maximum CPU utilization.