Operating Systems - Inode Structure - File Metadata & Block Pointers
A file system inode uses 12 direct pointers and one single indirect pointer. If a file size requires accessing the 300th data block, which pointer type will be used and why?
A file system inode uses 12 direct pointers and one single indirect pointer. If a file size requires accessing the 300th data block, which pointer type will be used and why?
medium🧠🧾 Concept Trace Q4 of Q15
Step-by-Step Solution
Solution:
Step 1: Calculate single indirect pointer coverage
Single indirect pointer points to a block containing multiple pointers. Assuming block size allows 256 pointers, single indirect covers blocks 13 to 268 (12 direct + 256).Step 2: Locate block 300
Block 300 is beyond single indirect coverage, so next level pointer is double indirect.Step 3: Confirm pointer type
Double indirect pointer points to blocks of pointers to data blocks, covering blocks beyond single indirect.Final Answer:
Option B -> Option BQuick Check:
Block 300 > 268, so double indirect pointer is used [OK]
Quick Trick: Single indirect covers limited blocks; double indirect covers more [OK]
Common Mistakes:
MISTAKES- Assuming single indirect covers all beyond direct pointers
Trap Explanation:
PITFALL- Candidates often overestimate single indirect pointer coverage or forget multi-level indirection.
Interviewer Note:
CONTEXT- Evaluates understanding of pointer coverage ranges and multi-level indirection.
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