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Question 19Asked in UGC NET Computer Science, June 2015 (Paper II & III, Selected Questions)

A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver…

A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?
  1. A0.984 sec
  2. B0.396 sec
  3. C0.738 sec
  4. D0.42 sec
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Correct answer: (D) 0.42 sec

Explanation

SSTF from cylinder 24: 24 → 26 (2) → 12 (14) → 8 (4) → 4 (4) → 42 (38) → 50 (8). Total distance = 70 cylinders. Seek time = 70 × 6 msec = 420 msec = 0.42 sec.

From UGC NET Computer Science PYQ, June 2015 (Paper II & III, Selected Questions)

This is question 19 of UGC NET Computer Science PYQ, June 2015 (Paper II & III, Selected Questions). See all questions of this paper with answers, or attempt the paper as a timed online test to get your score and all-India rank.