Question

Which one of the following CPU scheduling algorithms cannot be preemptive?

• A. Shortest Remaining Time First (SRTF) Scheduling
• B. First Come First Serve (FCFS) Scheduling
• C. Round Robin Scheduling
• D. Priority Scheduling

Hint:

Preemptive algorithms can interrupt a running process mid-execution; FCFS by definition runs each process to completion once started.

Answer 1

The Correct Option is B

Preemption means the CPU can be taken away from a running process before it finishes. SRTF constantly compares remaining times and switches to a shorter job, Round Robin switches processes every time quantum, and Priority scheduling can switch to a higher priority arrival, so all three support a preemptive version. FCFS, however, is defined purely by arrival order: once a process gets the CPU it keeps it until it completes or blocks itself, with no mechanism to interrupt it for another process. That rigid, non-interruptible nature is exactly why FCFS cannot be made preemptive, so the answer is option B.