Multiple choice

Consider the given queue. If the disk head is initially at 53, then what will be the total head movement using FCFS disk scheduling? 98, 183, 37, 122, 14, 124, 65, 67

  1. 620 cylinders

  2. 640 cylinders

  3. 520 cylinders

  4. 540 cylinders

  5. 635 cylinders
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B Correct answer
Explanation

We are using first come first serve disk scheduling and the disk is at 53 initially. It will then move to 98, then 98 to 183, 183 to 37, 37 to 122, 122 to 14 and so on till 65 to 67. So, the disk movements will be 98 - 53 = 45, 183 - 98 = 85, 183 - 37 = 146, 122 - 37 = 85, 122 - 14 = 108, 124 - 14 = 110, 124 - 65 = 59, 67 - 65 = 2. Now adding all the results 45 + 85 + 146 + 85 + 108 + 110 + 59 + 2 = 640

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