Operating Systems | Segmentation

A Memory Management technique in which memory is divided into variable sized chunks which can be allocated to processes. Each chunk is called a Segment.

A table stores the information about all such segments and is called Segment Table. 
Segment Table: It maps two dimensional Logical address into one dimensional Physical address.
It’s each table entry has
  • Base Address: It contains the starting physical address where the segments reside in memory.
  • Limit: It specifies the length of the segment.



Translation of Two dimensional Logical Address to one dimensional Physical Address.


Address generated by the CPU is divided into:
  • Segment number (s): Number of bits required to represent the segment.
  • Segment offset (d): Number of bits required to represent the size of the segment.
Advantages of Segmentation:
  • No Internal fragmentation.
  • Segment Table consumes less space in comparison to Page table in paging.
Disadvantage of Segmentation:
  • As processes are loaded and removed from the memory, the free memory space is broken into little pieces, causing External fragmentation.

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source and credits.
source and credits: http://www.geeksforgeeks.org
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