The sequence of pages which are to be referred by microprocessor is as follows:D,C,B,A,D,C,E,D,C,B,A,EThe number of page faults that will occur in the algorithm LRU with four page frames will be

To determine the number of page faults that will occur in the LRU algorithm with four page frames, we need to analyze the given sequence of pages: D, C, B, A, D, C, E, D, C, B, A, E.

1. Initially, all four page frames are empty.
2. The first page, D, is referenced. As the page frame is empty, a page fault occurs, and D is loaded into the frame.
3. The second page, C, is referenced. Again, a page fault occurs as the page frame is still empty. C is loaded into the frame.
4. The third page, B, is referenced. Another page fault occurs, and B is loaded into the frame.
5. The fourth page, A, is referenced. Once again, a page fault occurs, and A is loaded into the frame.
6. The fifth page, D, is referenced. This time, D is already present in the page frame, so no page fault occurs.
7. The sixth page, C, is referenced. C is also already present in the page frame, so no page fault occurs.
8. The seventh page, E, is referenced. As the page frame is full, a page fault occurs. The LRU algorithm determines that the least recently used page is B, so B is replaced with E.
9. The eighth page, D, is referenced. D is still present in the page frame, so no page fault occurs.
10. The ninth page, C, is referenced. C is also still present in the page frame, so no page fault occurs.
11. The tenth page, B, is referenced. B is no longer in the page frame since it was replaced with E earlier. Therefore, a page fault occurs, and B is loaded into the frame.
12. The eleventh page, A, is referenced. A is still present in the page frame, so no page fault occurs.
13. The twelfth page, E, is referenced. E is also still present in the page frame, so no page fault occurs.

In total, there are 4 page faults in the given sequence when using the LRU algorithm with four page frames.