Which CPU-scheduling algorithm is inherently pre-emptive because it allocates…

Concept

Pre-emptive scheduling allows the operating system to interrupt a running process and reassign the CPU before that process finishes.

An algorithm is inherently time-sliced when every ready process receives a bounded quantum and quantum expiry triggers pre-emption.

Application

Round Robin (RR) applies this rule through a circular ready queue.

1. Suppose the ready queue contains P1 followed by P2 and the time quantum is 4 ms.

2. Run P1 for at most 4 ms. If P1 is still unfinished when the quantum expires, the scheduler pre-empts it.

3. Place the unfinished P1 at the rear of the ready queue, then give P2 the next quantum.

4. Repeat the rotation. Queue removal and reinsertion are O(1) with a deque, while the quantum length controls response time and context-switch overhead.

Cross-check

Contrast the scheduling rules:

• First-Come, First-Served normally runs the current process until it blocks or completes.

• Shortest Job First is non-pre-emptive in its basic form; its pre-emptive counterpart is Shortest Remaining Time First.

• Priority scheduling may be either pre-emptive or non-pre-emptive, so its name alone does not imply a fixed quantum.

Therefore, the uniquely time-quantum-driven pre-emptive choice is Round Robin (RR).