Round-Robin Scheduler

Round-Robin Scheduler

A CPU scheduler built on a FIFO ready queue. The process at the FRONT runs for at most one quantum (time slice). If it still needs CPU time, it is enqueued again at the REAR; otherwise it finishes.

How to use it

• Enter a Burst (the total CPU time the process needs, 1–20) and press Add Process, or use Add Random. The simulator holds at most 6 processes.
• Quantum (1–10) is the length of one time slice.
• Run One Quantum executes a single slice; Run to End keeps going until every process has finished; Pause stops it; Reset empties the queue.
• Load Example loads a ready-made workload.

Reading the display

• Ready queue: the processes waiting for the CPU, front on the left and rear on the right.
• Running process: the process on the CPU, its remaining time and a progress bar.
• The bottom row shows the current operation, the clock, how many processes are ready and done, and the quantum.

Notes

• Every process gets the CPU at regular intervals, so none starves: the wait between two turns is at most (number of processes − 1) × quantum.
• A large quantum makes round robin behave like FCFS; a very small one causes a great many context switches.
• After a pause, the resumed process runs only for what is left of its quantum.
• Every dequeue and enqueue is O(1).