Difference between Paging and Segmentation

Paging and Segmentation are two memory management techniques used by operating systems to efficiently allocate memory to processes. Paging divides memory into fixed-size blocks, while segmentation divides it into variable-size logical units.

Paging

Paging is a memory management technique in which a process address space is broken into fixed-size blocks called pages (typically a power of 2, between 512 bytes and 8192 bytes). Main memory is similarly divided into fixed-size blocks called frames, with frame size equal to page size. This ensures optimum utilization of main memory and avoids external fragmentation.

Segmentation

Segmentation is a memory management technique in which each process is divided into several segments of different sizes, one for each logical module (main function, utility functions, data structures, etc.). Each segment represents a different logical address space. Segments are loaded into non-contiguous memory, but each individual segment occupies a contiguous block. The OS maintains a segment map table storing the starting address and length of each segment.

Key Differences

Conclusion

Paging divides memory into equal fixed-size blocks for simple and fast allocation but may cause internal fragmentation. Segmentation divides memory into variable-size logical units matching program structure but may cause external fragmentation. Many modern operating systems combine both techniques (segmented paging) to get the benefits of each.