Scheduler : It is a software of Operating System , which decides which process will go for execution and which process will go to ready state . Or It is a software which manages the process.
There are three types of schedulers :
- Long term scheduler (LTS) .
- Short term scheduler (STS).
- Medium term scheduler (MTS).
Long Term Scheduler : Long Term Scheduler is used to select process from the queue and loads them into the memory when the process change the state from new to ready , then there is use of LTS . In a simple way we can say that a scheduler which is used to select the process from secondary memory and transfer to the main memory is known as Long Term Scheduler .
Short Term Scheduler : Short Term Scheduler is also known as CPU scheduler or Dispatcher . Short Term Scheduler selects the process among the processes ,that are in ready state which are ready to execute and STS allocates the process to the CPU . which means STS decides which process will go for execution .
Medium Term Scheduler : It is a part of swapping . understand it with an example . a CPU select a process for execution and allocates the CPU . but that process needs peripheral (input output device) resource input . Then the CPU swap out the process from execution . and after the completion of input process will come back . which is swap in . and then it go for the execution .
