What are Schedulers in an Operating System? Detail the three primary types of…

Concept of OS Schedulers

Schedulers are specialized system software modules within an Operating System that manage process scheduling. Their main goal is to select processes from various system queues and determine how they allocate resources like Main Memory and the CPU.

Types of Schedulers

1. Long-Term Scheduler (Job Scheduler)

• Core Role: It selects processes from the job pool on the disk and loads them into the main memory's Ready Queue.

• Key Function: It directly controls the Degree of Multiprogramming (how many processes remain in memory at once).

• Frequency: It runs very slowly and infrequently, aiming to keep a balanced mix of CPU-bound and I/O-bound jobs.

2. Short-Term Scheduler (CPU Scheduler)

• Core Role: It selects an active process from the main memory's Ready Queue and allocates the CPU to it.

• Key Function: It maximizes CPU utilization and handles rapid context switching between processes.

• Frequency: It is the fastest scheduler in the system, executing continuously and rapidly in milliseconds.

3. Medium-Term Scheduler (Swapper)

• Core Role: It manages processes that get blocked or suspended due to I/O bottlenecks or memory shortages.

• Key Function: It removes active processes from main memory to the disk (Swapping Out) and brings them back (Swapping In) when memory is free.

• Frequency: It executes intermittently, focusing entirely on reducing memory congestion.

Technical Comparison Matrix