Saturday, 30 March 2013

Difference Between Paging and Segmentation

Characteristics
Paging
Segmentation
Definition
Paging breaks physical memory Into fixed-sized blocks called frames and logical memory into blocks of the same size called pages. When a process is to be  executed, its pages
are loaded into any available memory frames from the backing store. The backing store is divided into fixed sized blocks that are of the same size as the memory frames.
Segmentation is the division of computer’s primary memory into segments or sections. In segmentation, a reference to a memory location includes a value that identifies a segment and an offset within that  segment.
Length
All pages are divided into equal length.
The size of a memory segment is generally not fixed and may be as small as a single byte.
Logical Address Space
The user specifies only a single address, which is Partitioned by the hardware into a page number and an offset.
The addresses specify both the segment name And the offset within the segment. The user therefore specifies each address by two quantities: a segment name and an offset.
Fragmentation
Internal Fragmentation
External Fragmentation
Uses
To have more address space without having to buy more physical memory.
To allow programs and data to be broken up into independent address spaces and to aid sharing and protection.
Linking
Static Linking
Dynamic Linking

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