With__________, a page is written out to secondary memory only when it has been selected for replacement.

Explanation

Concept: In demand cleaning only when page has been selected for replacement then the page is written out to secondary memory. In pre-cleaning policy before the page frames are needed it writes modifies pages before their so that pages can be written out in batches Important Point Demand paging suggests keeping all pages of the frames in the secondary memory until they are required. In other words, it says that do not load any page in the main memory until it is required. If the referred page is not present in the main memory then there will be a miss and the concept is called Page miss or page fault Types of Page Replacement Methods FIFO Optimal Algorithm LRU Page Replacement FIFO (First-in-first-out) is a simple implementation method. In this method, memory selects the page for a replacement that has been in the virtual address of the memory for the longest time. The optimal page replacement method selects that page for a replacement for which the time to the next reference is the longest. The full form of LRU is the Least Recently Used page. This method helps OS to find page usage over a short period of time. This algorithm should be implemented by associating a counter with an even- page.