Q35,p3,j14. Consider a program that consists of 8 pages (from 0 to 7) and we have 4 page frames in the physical memory for the pages. The page reference string is : 1 2 3 2 5 6 3 4 6 3 7 3 1 5 3 6 3 4 2 4 3 4 5 1 The number of page faults in LRU and optimal page replacement algorithms are respectively (without including initial page faults to fill available page frames with pages) :

(A) 9 and 6

(B) 10 and 7

(C) 9 and 7

 (D) 10 and 6

Answer B.

 

Explanation.

In optimal page replacement theory, remove the page from frame, is not required in nearest future.

The page reference string is :

1 2 3 2 5 6 3 4 6 3 7 3 1 5 3 6 3 4 2 4 3 4 5 1

Optimal page replacement.

Page read	Page fault.	Frame(size=4)
1	0	1
2	0	12
3	0	123
2	0	123
5	0	1235
6	1	1356
3	1	1356
4	2	1364
6	2	1364
3	2	1364
7	3	1367
3	3	1367
1	3	1367
5	4	1365
3	4	1365
6	4	1365
3	4	1365
4	5	1345
2	6	2345
4	6	2345
3 4 5	6	2345
1	7	1345.

Similarly  LRU,FIFO