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    Question

    In a system using the Least Recently Used (LRU) page

    replacement algorithm, which of the following statements holds true? 
    A LRU replaces the page that has been in memory the longest Correct Answer Incorrect Answer
    B LRU can be implemented efficiently using a hash map and a queue Correct Answer Incorrect Answer
    C LRU replaces the page that has been accessed the least Correct Answer Incorrect Answer
    D LRU causes high page fault rates in large systems Correct Answer Incorrect Answer
    E LRU is less efficient than FIFO in systems with a large number of processes Correct Answer Incorrect Answer

    Solution

    The Least Recently Used (LRU) page replacement algorithm replaces the page that has not been used for the longest time. It can be implemented efficiently using a hash map and a doubly linked list or queue. The hash map is used to store the pages, and the linked list is used to track the most recently used pages. This ensures O(1) time complexity for both the lookup and replacement operations. Option A (Replaces the page that has been in memory the longest): This is incorrect. LRU replaces the least recently used page, not the one that has been in memory the longest. Option C (Replaces the page that has been accessed the least): LRU doesn’t replace the least accessed page; it replaces the least recently used page. A page could be accessed frequently but not recently. Option D (Causes high page fault rates in large systems): While LRU does result in page faults, it is no worse than other algorithms. In fact, LRU minimizes page faults compared to algorithms like FIFO. Option E (Less efficient than FIFO): LRU is generally more efficient than FIFO as it better tracks page usage history, whereas FIFO might replace a page that is frequently used but just older in the queue.

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