Operating Systems | Segmentation

3

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.

segmentation

 

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

Translation

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.

 

This article has been contributed by Vikash Kumar.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

 

 

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