GATE 2013 CS (CS1) – Question 39
A disk has sixteen surfaces, 16384 cylinders and 64 sectors per surface in a cylinder, with 512 bytes per sector. Address order is ⟨cylinder,surface,sector⟩. A 42797 KB file begins at ⟨1200,9,40⟩ and is contiguous. Find its last cylinder.
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Correct answer: (D) 1284
Explanation
A cylinder holds 16×64=1024 sectors, or 512 KiB. The file occupies 42797×2=85594 sectors and starts at within-cylinder sector 9×64+40=616. Its last sector’s relative index is 616+85594−1=86209. Dividing by 1024 gives floor 84. Thus the last cylinder is 1200+84=1284, D.