Operating Systems · Question 30 · Hard
Operating Systems question 30
A disk has cylinders 0 to 199 and the head is at cylinder 50, moving towards higher cylinder numbers. The request queue is 82, 170, 43, 140, 24, 16, 190. With SCAN (the head goes to the last cylinder, 199, before reversing), what is the total head movement?
- 314
- 332
- 391
- 208
Answer and explanation
Answer: B. 332
Explanation: The head moves 50 → 199 (149 cylinders), serving 82, 140, 170 and 190 on the way, then reverses to 16 (183 cylinders), serving 43 and 24. Total = 149 + 183 = 332. LOOK, which reverses at 190, would give 314.
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