My definition about LRU is Replace the page which one is Long-ago Used
1) no.of pages already loaded in the memory
given reference string is 1,2,4,5,6,1,2,3..... using demand-paging said that already two pages brought in main memory 1 ,2 and 1 is brought before 2
in the reference string very first 1 and 2 are hits but not the page faults
2) which page is long-ago used
given reference string is 1,2,4,5,6,1,2,3..... think each reference is in different month first 1 is in jan, first 2 is in feb, 4 is in mar, 5 is in apr, 6 is in may, second 1 is June , second 2 is in July etc... if a hit occurs consider the page respective month is updated to new one ( 1 is June and 2 is July in this example ). if a page fault occurs replace the page with which have long-ago referred...