Consider the following disc Queue with requests for I/O to block on cylinders:…

2025

Consider the following disc Queue with requests for I/O to block on cylinders:
45, 81, 185, 33, 175, 99, 150, 77
(Consider that the head starts from location 58)
What shall be the 2nd request being processed by C-LOOK (Right) disc Scheduling technique for the already given request queue?

  1. A.

    81

  2. B.

    45

  3. C.

    77

  4. D.

    33

Attempted by 237 students.

Show answer & explanation

Correct answer: A

Answer: 81

Explanation:

  • Start head position: 58.

  • Under C-LOOK (Right), serve requests with cylinder numbers greater than the head in ascending order, then jump (wrap) back to the smallest pending request and continue to the right.

  • Requests greater than 58, sorted ascending: 77, 81, 99, 150, 175, 185.

  • The first request served is 77 (the closest request to the right). The second request served is the next one to the right: 81.

  • After completing 185 (the largest), C-LOOK wraps to the smallest pending requests (33, 45), which are therefore served later.

Full service order (C-LOOK Right starting at 58):

  1. 77 (first)

  2. 81 (second)

  3. 99

  4. 150

  5. 175

  6. 185

  7. 33

  8. 45

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