Question

A computer has sixteen pages of virtual address space but the size of main memory is only four frames. Initially the memory is empty. A program references the virtual pages in the order of 0, 2, 4, 5, 2, 4, 3, 11, 2, 10. How many page faults occur if LRU page replacement algorithm is used?
1. 3
2. 5
3. 7
4. 8

Answer 1

Correct Answer - Option 3 : 7

Concept:

Least Recently Used (LRU) is a page replacement technique that replaces the least recently used page first from the frame in case of a page miss.

Explanation:

Page reference: 0, 2, 4, 5, 2, 4, 3, 11, 2, 10

Page replacement algorithm: Least Recently Used (LRU)

Frames	0	0	0	0	0	0	3	3	3	3
		2	2	2	2	2	2	2	2	2
			4	4	4	4	4	4	4	10
				5	5	5	5	11	11	11
M-Miss, H-Hit	M	M	M	M	H	H	M	M	H	M

LRU = 7 miss = 7-page faults

Hence correct answer is 7.