What is demand paging(OS-9)

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Demand paging

-Loading the entire program in the physical memory at program execution time is not so good because the user does not need the entire program in memory at a time.
-An alternative strategy is to load pages only as they are need this technique is known as demand paging.
-With demand paging virtual memory, pages are only loaded when they are demanded during program execution pages that are never accessed thus never loaded into physical memory.
  
-A demand paging system is a similar to paging system with swapping,
-But here it uses a lazy swap where it never swap a pages into memory unless that page will be need.
-In demand paging pager is more suitable than swap er. 

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