Operating Systems - Disk Scheduling - SSTF, SCAN, C-SCAN
A disk head is at track 100 moving towards higher track numbers. Pending requests are at 105, 110, 95, and 90. Using SCAN, which request will be serviced immediately after 110?
A disk head is at track 100 moving towards higher track numbers. Pending requests are at 105, 110, 95, and 90. Using SCAN, which request will be serviced immediately after 110?
medium🧠🧾 Concept Trace Q4 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand SCAN direction
Head moves up servicing 105 and 110, then reverses at the highest request or disk end.Step 2: After reaching 110, head reverses
It then services requests on the way back: 95, then 90.Step 3: Identify immediate next request after 110
First request on return is 95.Final Answer:
Option A -> Option AQuick Check:
SCAN reverses after highest request, servicing lower tracks next [OK]
Quick Trick: SCAN reverses direction after reaching highest or lowest request [OK]
Common Mistakes:
MISTAKES- Assuming SCAN skips lower requests
- Thinking SCAN revisits requests in same direction
Trap Explanation:
PITFALL- Candidates often think SCAN only moves in one direction without reversal, missing the return servicing.
Interviewer Note:
CONTEXT- Checks understanding of SCAN's bidirectional servicing behavior.
Master "Disk Scheduling - SSTF, SCAN, C-SCAN" in Operating Systems
Want More Practice?
15+ quiz questions · All difficulty levels · Free
Free Signup - Practice All QuestionsMore Operating Systems Quizzes