GATE CS 2015 Set 1 — Question 56

NAT+2 / -0MediumDisk Scheduling AlgorithmsI/O OrganizationComputer Organization & Architecture

Computer Organization & Architecture → I/O Organization → Disk Scheduling Algorithms

Last updated 5 September 2026

Question

Suppose the following disk request sequence (track numbers) for a disk with 100 tracks is given: 45, 20, 90, 10, 50, 60, 80, 25, 70. Assume that the initial position of the R/W head is on track 50. The additional distance that will be traversed by the R/W head when the Shortest Seek Time First (SSTF) algorithm is used compared to the SCAN (Elevator) algorithm (assuming that SCAN algorithm moves towards 100 when it starts execution) is_________tracks.

50 \to 45\,(5) \to 60\,(15) \to 70\,(10) \to 80\,(10) \to 90\,(10) \to 25\,(65) \to 20\,(5) \to 10\,(10)

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50 \to 45\,(5) \to 60\,(15) \to 70\,(10) \to 80\,(10) \to 90\,(10) \to 25\,(65) \to 20\,(5) \to 10\,(10)

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