This document shows the steps of an LRU (Least Recently Used) page replacement algorithm as it processes a reference string. Each line shows the reference string and the values in the page table as pages are accessed and the least recently used page is replaced if needed.

2. Counter REF string: 1 2 3 1 1 2 5 0 0 0

3. Counter REF string: 1 2 3 1 1 2 5 1 0 0 1 (0+1) = 1

4. Counter REF string: 1 2 3 1 1 2 5 1 0 1 1 2 (0+1) = 1

5. Counter REF string: 1 2 3 1 1 2 5 1 1 1 1 2 (0+1) = 1 3

6. Counter REF string: 1 2 3 1 1 2 5 2 1 1 1 2 (1+1) = 2 3

7. Counter REF string: 1 2 3 1 1 2 5 3 1 1 1 2 (2+1) = 3 3

8. Counter REF string: 1 2 3 1 1 2 5 3 1 2 1 2 (1+1) = 2 3

9. Counter REF string: 1 2 3 1 1 2 5 3 1 2 1 2 3 (3) ?

10. Counter REF string: 1 2 3 1 1 2 5 3 1 2 1 2 3 (3) ? (2) ?

11. Counter REF string: 1 2 3 1 1 2 5 3 1 2 1 2 3 (3) ? (2) ? (1) ?

12. Counter REF string: 1 2 3 1 1 2 5 3 1 2 1 2 3 1 < 2 < 3

13. Counter REF string: 1 2 3 1 1 2 5 3 1 2 1 2 5 1 < 2 < 3