Operating Systems MCQs with explanation

 Which of the following is Not a criterion for page replacement from main memory?

1. First in First Out(FIFO)
2. Least Recently Used(LRU)
3. Last in First Out(LIFO)
4. None of these

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Answer:

Option C: Last in First Out

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The page replacement algorithms are 

• FIFO
• LRU
• Optimal Page Replacement 
• Most Recently Used (MRU)

As we can see there is no LIFO algorithm.

What is Demand Paging?

Actually a file is divided into pages when it loaded into main memory for execution. Some times, whole file is not loaded into main memory, only when page is needed it loaded. This is called demand paging. 

Demand paging allows swap out of the pages which are not needed (main memory to secondary memory) and swap in of the pages which are needed (secondary memory to main memory).

In Demand paging the program or process is divided into several pages. Memory (i.e Main Memory or RAM) is divided into several frames. Instead of loading the entire program into memory, only essential pages are loading into memory.

Advantages of Demand Paging