In operating system, we have three types of schedulers-

  1. Long Term Scheduler(Job Term Scheduler)
  2. Short Term Scheduler(CPU Scheduler)
  3. Mid Term Scheduler(Medium Term Scheduler)
  1. Long Term Scheduler(LTS)- It is responsible for creating and bringing the new processor into the system.
  2. Short Term Scheduler(STS)- It is responsible for selecting one of the process from ready state onto scheduling to run state.
  3. Mid Term Scheduler(MTS)- it is responsible for suspending and resuming the process. The job done by MTS is called swapping.


  • Spooles- It is a special software to create job queue.
  • Dispatches- It is responsible for saving and loading the context of the process. The context switching will be done by dispatches. It is a slave of short term scheduler. Time spent on swapping of context switching is called  switching time or dispatch letancy. It is as much as reduce.


  1. Operating system process-  e.g schedulers, they are the processes written in operating system.
  2. User process-  e.g C programs / java programs.



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