There are 200 tracks on a disc platter and the pending requests have come in…
2014
There are 200 tracks on a disc platter and the pending requests have come in the order - 36, 69, 167, 76, 42, 51, 126, 12 and 199. Assume the arm is located at the 100 track and moving towards track 199. If sequence of disc access is 126, 167, 199, 12, 36, 42, 51, 69 and 76 then which disc access scheduling policy is used?
- A.
Elevator
- B.
Shortest seek-time first
- C.
C-SCAN
- D.
First Come First Served
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Correct answer: C
The disk arm starts at track 100 and moves towards higher tracks (199). It services requests in increasing order: 126, 167, 199. Upon reaching the end (199), it jumps to the lowest pending request (12) without reversing direction and continues servicing in increasing order: 36, 42, 51, 69, 76. This behavior of moving in one direction and wrapping around to the beginning is characteristic of the C-SCAN scheduling policy.
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