What Is Segmentation In OS

What Is Segmentation In OS

what is segmentation in os

What Is Segmentation In OS

What Is Segmentation In OS

What Is Segmentation In OS


What Is Segmentation In OS



Segmentation in OS (OS Full Form-Operating Systems) is a memory management technique that divides the main memory into logical segments. In this blog, we will explain what is segmentation in OS, explaining how it works, types of segmentation operating systems. 

What Is Segmentation In OS

Computer main memory is segmented into variable-sized units via segmentation. 

Such as: A 1000-byte computer is yours. Run a 500-byte application. Because the software doesn’t require all the RAM, loading it all at once wastes 500 bytes.

Segmentation divides the program into two parts: 

  • Code section
  • Data segment

Code and data segments hold the program’s instructions and data, respectively. Segments have segment numbers.

The OS places each segment in memory when the application is loaded. The data segment may be loaded at 500 and the code section at 0.

When the program executes, it references memory locations using a two-part address:

1) Segment number

2) offset

The segment number tells the OS which segment the memory location is in. The offset tells the OS how far from the beginning of the segment the memory location is.

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Why Segmentation Is Required

In traditional memory management, we have been using a technique called “paging”.” Paging is primarily focused on the operating system’s perspective rather than the user’s needs. It divides processes into fixed-sized pages, regardless of whether certain parts of a process should be grouped together.

It’s annoying for users since conceptually related functions may be spread across pages. This reduces system efficiency and performance.

“Segmentation” memory management is superior.  It retains a program’s logical structure and user-meaningful organization also boosts system performance by grouping similar pieces.

With segmentation, the operating system recognizes the user’s view of the process and ensures that segments are loaded together into memory when needed. This results in faster access to functions and better overall system performance.

Segmentation ensures that the user’s perspective is considered, resulting in a more effective and user-friendly memory management technique.

Types Of Segmentation

There are Two Types Of Segmentation: 

1) Simple Segmentation

Basic segmentation, or simple segmentation, splits memory into logical pieces depending on program demands. Each segment—code, data, stack, etc.—represents a process step. Processes determine segment size. Simple segmentation protects processes by preventing them from accessing each other’s memory. It simplifies code and data sharing and memory allocation.

2) Virtual Memory Segmentation

Virtual memory segmentation is a combination of segmentation and paging techniques. It involves dividing the logical address space of a process into segments and further dividing these segments into fixed-sized pages. Each segment can have multiple pages, and pages are mapped to physical memory frames using a page table. This approach provides the benefits of both segmentation and paging, allowing for efficient memory management and addressing larger address spaces than the physical memory can accommodate. Virtual memory segmentation allows processes to have more memory than physically available and enables efficient memory allocation and swapping of pages between disk and memory.

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Difference Between Paging Vs Segmentation

Basic IdeaDivides memory into fixed sized pagesDivides memory into logical segments
Memory AllocationAllocates memory in equal sized pagesAllocates memory in variable sized segments
FragmentationCan lead to external fragmentationCan lead to internal fragmentation
FlexibilityProvides flexibility in memory allocation and utilizationProvides flexibility in organizing and sharing code/data
Process ViewIndependent of the process’s logical structureConsiders the logical structure of the process
Hardware SupportRequires hardware support for page mappingRequires hardware support for segment mapping

Advantages Of Segmentation

  • Logical organization based on program structure
  • Process isolation and protection
  • Flexible memory allocation
  • Code and data sharing
  • Support for virtual memory systems
  • Enhanced program modularity and readability
  • Efficient memory utilization by dynamically adjusting segment sizes
  • Reduced redundancy through shared libraries and data.
  • Improved system performance through optimized memory access.
  • Facilitates the execution of larger programs by providing a larger address space.

Disadvantages Of Segmentation

  • Increased complexity in memory management due to the need for segment tables and segment descriptors.
  • When segments are not fully utilized, there is a possibility of internal fragmentation occurring.
  • Difficulty in handling dynamic memory allocation within segments.
  • Allocating segments non-contiguously in memory can lead to the potential for external fragmentation.
  • Overhead of managing segment registers and maintaining segment information.
  • The efficient management of a large number of segments can be limited in terms of scalability.
  • Challenges in sharing and synchronizing data across different segments.
  • Potential for increased overhead and slower performance due to frequent segment switches.
  • Complication in handling memory protection mechanisms across multiple segments.
  • Difficulty in optimizing memory access patterns due to non-contiguous segment allocation.


Segmentation in operating systems brings logical organization and flexibility to memory management. It divides processes into segments based on their components, improving program structure and readability. Understanding segmentation provides a solid foundation for diving deeper into this critical aspect of operating system functionality. I hope you get a better understanding of “What Is Segmentation In OS”.

Keep Learning, Keep Growing!!!


What Is Segmentation In Os?

Segmentation in operating systems is a memory management technique that divides the main memory into logical segments.

Why is segmentation used in OS?

Segmentation is used to simplify memory allocation and access control in OS, providing flexibility for processes.

What are the 4 types of segmentation?

The four types of segmentation are:

  • Null segment
  • Code segment
  • Data segment
  • Stack segment


What is the best use of segmentation?

Segmentation is best used for managing memory in systems where processes have varying memory requirements, as it allows for more flexible allocation and sharing.



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