Disk Scheduling Calculator
SCAN sweeps to one end and back like an elevator: from cylinder 53 this queue needs 236 cylinders of head movement.
236 cylinders
- Average seek per request
- 29.5 cylinders
- Service order
- 53 → 37 → 14 → 0 → 65 → 67 → 98 → 122 → 124 → 183
Step-by-step solution
- Head starts at 53
- Order: 53 → 37 → 14 → 0 → 65 → 67 → 98 → 122 → 124 → 183
- Total = 16 + 23 + 14 + 65 + 2 + 31 + 24 + 2 + 59 = 236
Disk Scheduling Formula
total movement = Σ |cylinderᵢ₊₁ − cylinderᵢ|
SCAN goes to the disk end; LOOK turns at the last request
Worked Example
Requests 98, 183, 37, 122, 14, 124, 65, 67 with the head at 53 moving towards 0, SCAN:
- Head starts at 53
- Order: 53 → 37 → 14 → 0 → 65 → 67 → 98 → 122 → 124 → 183
- Total = 16 + 23 + 14 + 65 + 2 + 31 + 24 + 2 + 59 = 236
Service order: 53 → 37 → 14 → 0 → 65 → 67 → 98 → 122 → 124 → 183
GATE tip
Check whether the question counts the C-SCAN return seek; GATE answer keys have used both conventions, so both totals are shown.
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Frequently asked questions
What is the difference between SCAN and LOOK?
SCAN travels to the last cylinder before reversing; LOOK reverses at the last pending request, saving the extra travel.
Is the C-SCAN return jump counted?
Textbooks differ. This calculator includes it in the total and shows the movement without it as well.
Sources
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Disk Scheduling Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/disk-scheduling-calculator/
IEEE
Scientific Converters, "Disk Scheduling Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/disk-scheduling-calculator/