GATE CS 2002 Q1.22 — CPU Scheduling

A scheduling algorithm is non-preemptive if a process, once allocated the CPU, holds it until it voluntarily releases it (either by terminating or by transitioning to a waiting state for I/O).

• First-In First-Out (FIFO): This is a strictly non-preemptive algorithm. Processes are dispatched in the order of their arrival, and a running process executes to completion or until it blocks for I/O.
• Round Robin (RR): This is inherently preemptive. It uses a time quantum to preempt the currently running process and allocate the CPU to the next process in the ready queue.
• Multilevel Queue Scheduling & Multilevel Feedback Queue (MLFQ): These algorithms typically employ preemption to ensure that higher-priority processes can preempt lower-priority ones, or to enforce time slices across different queues.

Thus, First-In First-Out (FIFO) is the only strictly non-preemptive scheduling algorithm among the given options.