Day 01 Part 17(A)- Schedulers in operating system long term, short term and midium term schedulers.

Day 01 Part 17(A)- Schedulers in operating system long term, short term and midium term schedulers

 Schedulers in Operating System (OS) – Long-Term, Short-Term & Medium-Term Schedulers

Schedulers in an Operating System (OS) are responsible for managing process execution by selecting processes to run in the CPU. There are three types of schedulers:

Long-Term Scheduler (Job Scheduler)
Short-Term Scheduler (CPU Scheduler)
Medium-Term Scheduler (Swapper)

 Long-Term Scheduler (Job Scheduler)

Function: Selects which processes should be admitted into the ready queue from the job pool.
Frequency: Runs infrequently (e.g., once every few seconds or minutes).
Main Purpose: Controls degree of multiprogramming (number of processes in memory).
Works in: Batch Systems (e.g., old mainframe systems).
Example: If there are 100 processes in the job pool, the long-term scheduler chooses 10 to bring into RAM.

Key Role: Determines which programs enter execution.

 Short-Term Scheduler (CPU Scheduler)

Function: Selects which process will execute next in the CPU from the ready queue.
Frequency: Runs very frequently (millisecond level).
Main Purpose: Decides which process gets CPU time for execution.
Works in: All systems (Batch, Time-Sharing, Real-Time).
Example: A process in the ready queue gets scheduled every few milliseconds for execution.

Key Role: Improves CPU utilization & response time.

 Medium-Term Scheduler (Swapper)

Function: Removes some processes from memory (swaps out) and brings them back later (swaps in).
Frequency: Runs occasionally, based on memory needs.
Main Purpose: Reduces memory load and improves CPU efficiency.
Works in: Time-Sharing & Virtual Memory Systems.
Example: If RAM is full, it moves an inactive process to disk (swap space) and loads an active process.

Key Role: Manages swapping of processes to optimize RAM usage.

 Comparison of Schedulers

 Key Points to Remember

Long-Term Scheduler → Decides which jobs enter execution
Short-Term Scheduler → Decides which job gets CPU time
Medium-Term Scheduler → Decides which jobs to swap (suspend/resume)

Would you like examples of scheduling algorithms like FCFS, Round Robin, or Priority Scheduling?

Day 01 Part 17(A)- Schedulers in operating system long term, short term and midium term schedulers.