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

Step 1: Recall the definition of preemptive scheduling: a running process can be forcibly removed from the CPU before it finishes or voluntarily blocks.
Step 2: Check each option. SRTF compares the remaining burst time of the running process with newly arrived processes and can preempt, so it is preemptive. Round Robin preempts a process when its time quantum expires, so it is preemptive. Priority Scheduling can be implemented in a preemptive form where a higher priority process arriving later preempts the running one.
Step 3: First Come First Serve, FCFS, always runs a process to completion, or until it blocks, once it starts; by definition it never preempts a running process, so FCFS cannot be preemptive.
Final Answer: FCFS Scheduling (Option B)