CPU Scheduling

CPU Scheduling

Processes move between Not arrived, the ready queue, the CPU and Finished while the Gantt chart is drawn one time unit at a time. The table on the right shows each process’s waiting (W), turnaround (T) and response (R) time as it finishes, with the averages underneath.

How to use

• Pick an algorithm and a scenario, or edit the process table directly (name, arrival, burst, priority; + adds a process, up to 8; × removes one).
• ▶ plays; the step buttons move one time unit back or forward, or jump to the start or end. Speed sets time units per second.
• Quantum is the Round Robin time slice (1–10).
• Compare runs all six algorithms on the same processes and sweeps the RR quantum from 1 to 6; click an algorithm there to switch to it.

Algorithms

FCFS

Run in arrival order, to completion.

SJF

Shortest burst among arrived; no preemption.

SRTF

Shortest remaining time; arrivals can preempt.

Priority

Smallest number first; no preemption.

P-Priority

A strictly higher priority arrival preempts.

RR

One quantum per turn, then back of the queue.

Ties

Earlier arrival, then table order. RR: arrivals queue before the preempted process.

Metrics

T

Turnaround = completion − arrival

W

Waiting = turnaround − burst

R

Response = first run − arrival

Legend

Keys