Explain Three types of process schedulers?

1. Long-term scheduler: The long-term scheduler, also known as the admission scheduler, is responsible for selecting which processes from the job pool should be loaded into the ready queue for execution. It determines the degree of multiprogramming by deciding how many processes can be in the ready queue at a given time. The long-term scheduler is typically invoked less frequently compared to other schedulers, as its main goal is to maintain a balance between the degree of multiprogramming and system performance.

2. Short-term scheduler: The short-term scheduler, also known as the CPU scheduler, is responsible for selecting which process from the ready queue should be executed next by the CPU. It makes decisions on a very frequent basis, often multiple times per second, to ensure that processes are executed in a fair and efficient manner. The short-term scheduler is crucial for optimizing CPU utilization and minimizing response time for processes.

3. Medium-term scheduler: The medium-term scheduler, also known as the swapping scheduler, is responsible for deciding which processes should be swapped out of main memory and onto the disk to free up space for other processes. This scheduler is invoked when the system is under memory pressure and needs to free up memory for new processes. The medium-term scheduler helps in preventing thrashing and ensures that the system can efficiently manage its memory resources.

1. Long-Term Scheduler (Job Scheduler)

- Selects processes to be brought into the ready queue from the pool of available processes.
- Considers factors such as process priority, resource requirements, fairness, and load balancing across multiple CPUs.
- Aims to maximize overall system throughput and minimize average waiting time.

2. Medium-Term Scheduler (Swap Scheduler)

- Controls the swapping of processes between memory and disk.
- Decides which processes to swap out to disk to make room for incoming processes that require more memory.
- Balances the need to keep frequently used processes in memory with the need to accommodate new processes.

3. Short-Term Scheduler (CPU Scheduler)

- Selects which ready process to run on the CPU next.
- Uses a scheduling algorithm to decide the order of execution, such as:
- First-Come-First-Served (FCFS): Processes are executed in the order they arrive in the ready queue.
- Shortest Job First (SJF): Process with the shortest estimated execution time is executed next.
- Round-Robin: Processes are executed in a circular fashion, giving each process a fixed time quantum to run.
- Priority Scheduling: Processes with higher priority are given preferential treatment.