A disk has cylinders 0 to 199. The head is at 50 and is moving toward higher cylinders. The pending requests are 82, 140, 20 and 10. Under SCAN, which request will be serviced first?

Options

  • A. 20
  • B. 10
  • C. 82
  • D. More than one of the above
  • E. None of the above

Correct Answer (Detailed Explanation is Below)

C. 82

Detailed Explanation

Explanation: Since the head is initially moving toward higher-numbered cylinders, SCAN first services requests in that direction. Among the pending requests, 82 is the nearest request in the upward direction and will therefore be serviced first.

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