Consider a disk queue with requests for I/O to blocks on cylinders. 98 183 37…
2024
Consider a disk queue with requests for I/O to blocks on cylinders. 98 183 37 122 14 124 65 67. Considering FCFS (first cum first served) scheduling, the total number of head movements is, if the disk head is initially at 53 is?
Answer: C. 640 — FCFS sequence (start at 53): 53 → 98 → 183 → 37 → 122 → 14 → 124 → 65 → 67 Head movements: |53−98|=45, |98−183|=85, |183−37|=146, |37−122|=85, |122−14|=108,…
- A.
600
- B.
620
- C.
640
- D.
650
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Correct answer: C
FCFS sequence (start at 53): 53 → 98 → 183 → 37 → 122 → 14 → 124 → 65 → 67 Head movements: |53−98|=45, |98−183|=85, |183−37|=146, |37−122|=85, |122−14|=108, |14−124|=110, |124−65|=59, |65−67|=2 Total = 45+85+146+85+108+110+59+2 = 640 tracks.
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