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    Question

    A disk scheduling system receives requests for the

    following cylinders: 98, 183, 37, 122, 14, 124, 65, 67. If the current position of the disk head is at cylinder 53, and the system uses the SCAN algorithm, which cylinder is serviced immediately after 65?
    A 67 Correct Answer Incorrect Answer
    B 14 Correct Answer Incorrect Answer
    C 37 Correct Answer Incorrect Answer
    D 98 Correct Answer Incorrect Answer
    E 122 Correct Answer Incorrect Answer

    Solution

    The SCAN algorithm moves the disk head in one direction, servicing all requests until it reaches the end, then reverses direction. 1. Initial direction: upwards. 2. Sequence of servicing: 65 → 67 → 98 → 122 → 124 → (reverses) → 37 → 14. 3. After servicing 65, the next request in the upward direction is 67. Why Other Options Are Incorrect: • B) 14 & C) 37: These are serviced after the head reverses direction. • D) 98 & E) 122: These are serviced later in the upward direction, but after 67.

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