The head of a moving-head disk with 200 tracks, numbered 0 to 199, has just finished a request at track 125 and is currently serving a request at track 143. The queue of requests in FIFO order is 86, 147, 91, 177, 94, 150, 102, 175, 130. What will be the total number of head movements required to satisfy these requests with the SCAN algorithm?
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Correct answer: B. 169 cylinders
Explanation
The head is moving upward (125 → 143). SCAN serves 147, 150, 175, 177, goes to the end 199 (56 cylinders), then reverses and serves 130, 102, 94, 91, 86 (199 − 86 = 113). Total = 56 + 113 = 169.More System Software and Operating System questions
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