How to use the Disk Scheduling Algorithm Simulator
- 1. Enter the requestsThe cylinder numbers in the queue, the head's start and the disk size.
- 2. Pick optionsOne algorithm or all six, the direction, and whether to count the C-SCAN return jump.
- 3. CompareSee each algorithm's order and total head movement.
The six algorithms
- FCFS: serve requests in arrival order. Fair, but the head may zig-zag.
- SSTF: always serve the nearest request next. Low seek time, but far requests can starve.
- SCAN (elevator): sweep one way to the end of the disk, then reverse.
- C-SCAN: sweep one way to the end, jump back to the other end, and sweep the same way again, giving more even waiting times.
- LOOK and C-LOOK: like SCAN and C-SCAN, but turn at the last request instead of going to the disk's edge.
Textbooks disagree on one detail: whether the C-SCAN and C-LOOK jump back counts as head movement. The checkbox lets you match your syllabus, and every order served is listed so you can check the total by hand.
Worked example
The sample is the standard textbook queue 98, 183, 37, 122, 14, 124, 65, 67 with the head at 53 on a 200-cylinder disk (0 to 199), moving towards higher numbers:
- FCFS: 640 cylinders.
- SSTF: 236 (53 → 65 → 67 → 37 → 14 → 98 → 122 → 124 → 183).
- SCAN: 331 (up to 199, then back down to 37 and 14).
- C-SCAN: 382 counting the jump from 199 back to 0.
- LOOK: 299; C-LOOK: 322.
SSTF wins here, with an average seek of 29.50 cylinders per request. Switch the direction to towards 0 and SCAN drops to 236 and LOOK to 208, which shows how much the starting direction matters.
Frequently asked questions
Which algorithm is best?
It depends on the load. SSTF and LOOK give low totals; C-SCAN and C-LOOK give fairer waiting times. Modern drives and SSDs schedule internally.
Is the disk size needed for LOOK?
No, but SCAN and C-SCAN go to the edge, so they need it.
Why is my answer different from my book's?
Check the direction and whether your book counts the return jump; both change the total.
Is the disk scheduling algorithm simulator free to use?
Yes, the disk scheduling algorithm simulator is free and costs nothing. Your first simulation shows a short form for your name and WhatsApp number one time; once that's done, this tool and every other Uncodemy tool open with no form.