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Difference between Demand Paging and Segmentation

Last Updated : 24 Mar, 2023
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Demand Paging: Demand paging is identical to the paging system with swapping. In demand paging, a page is delivered into the memory on demand i.e., only when a reference is made to a location on that page. Demand paging combines the feature of simple paging and implement virtual memory as it has a large virtual memory. Lazy swapper concept is implemented in demand paging in which a page is not swapped into the memory unless it is required. Segmentation: Segmentation is the arrangement of memory management. According to the segmentation the logical address space is a collection of segments. Each segment has a name and length. Each logical address have two quantities segment name and the segment offset, for simplicity we use the segment number in place of segment name. The difference between Demand Paging and Segmentation are as follows:

S.No. Demand Paging Segmentation
1. In demand paging, the pages are of equal size. While in segmentation, segments can be of different size.
2. Page size is fixed in the demand paging. Segment size may vary in segmentation as it grants dynamic increase of segments.
3. It does not allows sharing of the pages. While segments can be shared in segmentation.
4. In demand paging, on demand pages are loaded in the memory. In segmentation, during compilation segments are allocated to the program.
5. Page map table in demand paging manages record of pages in memory. Segment map table in segmentation demonstrates every segment address in the memory.
6. It provides large virtual memory and have more efficient use of memory. It provides virtual memory and maximum size of segment is defined by the size of memory.
7. Virtual memory is divided into pages. Virtual memory is divided into segments.
8. Size of Unit of demand Paging  Pages can be of equal or variable size. Size of Unit of segmentation Segments are variable in size.
9. Memory allocation of Pages are allocated dynamically. Memory allocation of Segments are allocated at the process start.
10. Memory access is  Page-level protection. Memory access is  segment-level protection.
11. Memory wastage is Internal fragmentation. Memory wastage is external  fragmentation.
12. Paging algorithm is Demand Paging. Paging algorithm is non- demand Paging(Fixed Allocation).

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