Question

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, the number of page transfers with an empty internal store of 3 frames is :

In question 2, if the number of page frames is increased to 4, then the number of page transfers :
a) decreases
b) increases
c) remains the same
d) None of these

Answer 1

When using FIFO page replacement with 3 frames, there are 9 page transfers, and this number decreases to 5 when the number of page frames is increased to 4, meaning that fewer page faults occur with more available memory.

Step-by-step explanation:

The student is inquiring about page replacement using the First-In-First-Out (FIFO) algorithm. With 3 frames and the given sequence of page references, the number of page transfers (page faults) will be as follows:

A, B, C

: first three pages load into the frames with 3 page transfers.

D

: replaces A, 1 more page transfer.

A

: replaces B, 1 more page transfer.

B

: replaces C, 1 more transfer.

E

: replaces D, 1 transfer.

A

: replaces A (no transfer as it's already in the frame).

B

: replaces B (no transfer),

C

: replaces E, 1 transfer.

D

: replaces A, 1 more transfer.

E

: replaces B, 1 more transfer.

Overall, that's 9 page transfers. If the number of page frames increases to 4, the number of page transfers:

• A, B, C, D: Load with 4 transfers, no replacement needed initially.
• A: Already in a frame (no transfer).
• B: Already in a frame (no transfer).
• E: Loads into the empty frame (1 transfer).
• A, B, C, D: All are already in frames (no transfers).
• E: Already in a frame (no transfer).

With 4 frames, this results in a total of 5 transfers. Therefore, the number of page transfers decreases when the number of page frames is increased from 3 to 4.