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Process Scheduling And Types of Process Schedular :-


 
      ⇰ PROCESS SCHEDULING
Process Scheduling is a task  of Operating System that schedules processes of different states like new, ready, waiting, terminated  and running.This scheduling helps in allocation of CPU time for each process, and Operating System allocates the CPU time for each procss. And the process scheduling plays important role to keep the CPU busy all the time. 
⏩   Followings are some objectives of Process Scheduling :-
 i > To increase the amount of users within acceptable response times.

  ii > To maintain the balance between response and utilization of system.

 iii > To decrease the enforce priorities and give reference to the processes holding the key resources.
  
  ⇰  PROCESS SCHEDULAR
A scheduler carries out the process scheduling work. Schedulers are often implemented so they keep all computer resources busy and allows multiple users to share system resources  to achieve  multiprogramming.
 There are  mainy three types of process scheduler :-
   i > Long Term schedular.
  ii > Short Term schedular.
 iii >  Mediam Term schedular.
  
i > Long Term   :-  It is also known as Job Schedular. This schedular selects  new process  from queue and loads into memory for  execution.  It controls Degree of Multi-programming means maintains number of process present in ready state at a particular time. The main goal of this scheduler is to offer a balanced mix of jobs, like Processor, I/O jobs., that allows managing multiprogramming.


ii > Short term schedular :- This schedular is also known as CPU scheduler.  The main goal of this scheduler is to boost the system performance according to set criteria.   It is responsible for selecting one process from ready state for scheduling it on the running state. Dispatcher is responsible for loading the process selected by Short-term scheduler on the CPU. The dispatcher gives control of the CPU to the process selected by the short term scheduler.
 A dispatcher does the following works:-
∗ Switching context.
∗ Switching to user mode.
∗ Jump to the proper location in the newly loaded program.


 iii > Medium-term scheduler :-  This schedular is an important part of swapping. It enables handling the swapped out-processes.   It is responsible for suspending and resuming the process based on I/O request of process. A running process can become suspended if it makes an I/O request. A suspended processes can't make any progress towards completion. In order to remove the process from memory and make space for other processes, the suspended process should be moved to secondary storage.
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