Computer JE exam

Question

consider the following page reference string: 1, 2, 3, 4, 1, 2,5, 1, 2,3,4,5 if program contains 4 page frames then what is difference between page faults obtained using FIFO and optimal page replacement algorithms     

option a . 10

option b . 6

option c . 4

option d . 3

Answer 1

Answer: option c. 4

FIFO

1  5  4

2  1  5

3   2

4   3

 

No. of page faults in FIFO page replacement algorithm = 10

OPTIMAL

1   4

2

3

4   5

 

No. of page faults in OPTIMAL page replacement algorithm = 6

So the difference in the page faults = 10-6 = 4