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Which of the following best describes the LOOK disk scheduling algorithm?

easy🧠 Conceptual Q2 of Q15
LLD - Design — Elevator System
Which of the following best describes the LOOK disk scheduling algorithm?
AIt moves the head to the end of the disk before reversing direction
BIt always services the request closest to the current head position
CIt moves the head only as far as the last request in each direction before reversing
DIt services requests in the order they arrive without reordering
Step-by-Step Solution
Solution:

  1. Step 1: Understand LOOK algorithm behavior

    LOOK moves the head only up to the last request in the current direction, then reverses.

  2. Step 2: Compare with SCAN

    Unlike SCAN, LOOK does not go to the disk's end if no requests are there.

  3. Final Answer:

    It moves the head only as far as the last request in each direction before reversing -> Option C

  4. Quick Check:

    LOOK limits head movement to last request in direction [OK]
Quick Trick: LOOK stops at last request before reversing direction [OK]
Common Mistakes:
MISTAKES
  • Confusing LOOK with SCAN going to disk end
  • Assuming LOOK services requests randomly
  • Thinking LOOK always services closest request first

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