A process refers to 5 pages A, B, C, D, E in the order: A; B; C; D; A; B; E;…

2018

A process refers to 5 pages A, B, C, D, E in the order: A; B; C; D; A; B; E; A; B; C; D; E If the page replacement algorithm is FIFO, then the number of pages which transfer from an empty internal store of 3 frames is —

  1. A.

    8

  2. B.

    10

  3. C.

    9

  4. D.

    7

Attempted by 242 students.

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Correct answer: C

FIFO algorithm with 3 frames (initially empty):

  1. Reference 1: A → Frames: [A] ; Page fault (1)

  2. Reference 2: B → Frames: [A, B] ; Page fault (2)

  3. Reference 3: C → Frames: [A, B, C] ; Page fault (3)

  4. Reference 4: D → Evict oldest (A) → Frames: [B, C, D] ; Page fault (4)

  5. Reference 5: A → Not in frames, evict oldest (B) → Frames: [C, D, A] ; Page fault (5)

  6. Reference 6: B → Not in frames, evict oldest (C) → Frames: [D, A, B] ; Page fault (6)

  7. Reference 7: E → Not in frames, evict oldest (D) → Frames: [A, B, E] ; Page fault (7)

  8. Reference 8: A → A is in frames [A, B, E] ; Hit (no page fault)

  9. Reference 9: B → B is in frames [A, B, E] ; Hit (no page fault)

  10. Reference 10: C → Not in frames, evict oldest (A) → Frames: [B, E, C] ; Page fault (8)

  11. Reference 11: D → Not in frames, evict oldest (B) → Frames: [E, C, D] ; Page fault (9)

  12. Reference 12: E → E is in frames [E, C, D] ; Hit (no page fault)

Total page transfers = 9. Each page fault causes a transfer, so transfers = 9.

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