Have you ever found yourself helpless when loading a file and waiting for your system to respond in operating with a file or program. And then you start wondering whether or not there is a better and more efficient method of obtaining images by computers more quickly and smoothly.
In this blog, let us learn how segmentation in operating system can help us solve our problems quickly.
What is Segmentation in Operating Systems?
Segmentation in Operating system is a process that divides memory into logical parts called segments and each segment is listed with a unique identifier called segment number. The segmentation is used to locate the segment in the computer memory. Segmentation prevents one program from accessing the segment part of the other programs.
You can share multiple programs to share the same segment and can also be used to implement virtual memory. It is a memory management technique which can divide an application virtual address space into unique sections.
Why Is Segmentation Needed In Operating System?
Segmentation in operating system is essential for efficient memory management and program execution. Before segmentation, a large program is treated as a single entity, making memory allocation rigid and less organized.
After segmentation in operating system, the program is divided into smaller, manageable segments, improving organization and modularity. In terms of efficiency and speed, the operating system previously had to search the entire memory space to locate data, whereas with segmentation, it can quickly identify the relevant segment and retrieve the data efficiently. Memory usage also becomes more flexible since, before segmentation, all programs were allocated the same amount of memory, leading to wastage.
After segmentation, memory is allocated dynamically based on the program’s needs, optimizing utilization. Another major advantage is the prevention of internal fragmentation before segmentation, memory fragmentation occurred frequently, leading to inefficient space usage, while segmentation minimizes or eliminates internal fragmentation.
As a result, system performance improves because memory allocation and deallocation, which were previously slow and inefficient, now become faster and more effective. Lastly, security and isolation are significantly enhanced, as before segmentation, programs could access each other’s memory, potentially leading to security risks. With segmentation, programs are isolated, preventing unauthorized access and modifications, ensuring a more secure computing environment.
Read more: What is Fragmentation in Operating System?
Paging Vs Segmentation in Operating System
Let us check some of the major differences between the paging and operating system below.
| Paging | Segmentation |
| In Paging memory is divided into fixed-size blocks called pages. | In segmentation memory is divided into variable-sized blocks called segments. |
| In Paging pages have a fixed size (e.g., 4KB, 8KB). | Segmentation segments have a variable size based on program needs. |
| The Paging process divides process memory into equal-sized pages. | Segmentation divides process memory into logical segments like code, data, and stack. |
| It uses a page number and offset. | It uses a segment number and offset. |
| Paging causes internal fragmentation due to fixed page size. | Segmentation in operating system causes external fragmentation, but no internal fragmentation. |
| It is less flexible since pages are fixed in size. | It is more flexible as segments vary in size based on program structure. |
| Paging parses a page table to map logical to physical addresses. | It uses a segment table to map logical to physical addresses. |
| Paging is used in virtual memory for efficient memory allocation. | It is used when programs need logical division (e.g., code, stack, heap). |
| It has faster access due to uniform page sizes. | It may take longer due to varying segment sizes. |
| It is harder to implement specific access control for individual data sections. | It is easier to enforce access control on different segments (e.g., read-only code). |
How Does Segmentation Work In Operating System?
Segmentation is a memory management technique used to divide a memory into local segments unlike paging where memory is divided into fixed size pages.
1. Dividing the Program into Segments
- A program is logically divided into segments such as code, data, stack, and heap.
- Each segment has a variable size, depending on the amount of memory required.
2. Assigning Segment Numbers
- Each segment is assigned a segment number for identification.
- The OS maintains a Segment Table that records segment details.
3. Logical to Physical Address Translation
- A logical address in segmentation consists of:
- Segment Number (identifies the segment)
- Offset (distance within the segment)
- The OS uses the Segment Table to map the segment number to its base address in physical memory.
- The final physical address is calculated as:
Physical Address=Base Address+OffsetPhysical Address=Base Address+Offset
4. Memory Allocation and Access
- The OS allocates memory dynamically to each segment as needed.
- When a process needs to access data, the OS looks up the Segment Table, finds the base address, and adds the offset to access the exact location.
5. Protection and Isolation
- The OS applies access permissions to each segment (e.g., read-only for code, read-write for data).
- This prevents unauthorized access between processes, enhancing security.
Let us understand the working of Segmentation in operating system with the help of a simple example below. Consider a process divided into the following segments:
| Segment | Function | Size (KB) | Base Address |
| 0 | Code | 10 KB | 1000 |
| 1 | Data | 5 KB | 2000 |
| 2 | Stack | 8 KB | 3000 |
If a process requests data from Segment 1 (Data Segment) at Offset 3 KB, the OS calculates the physical address as:
Physical Address=Base Address of Segment 1+Offset=
2000+3000=5000
The OS retrieves the data from memory location 5000.
Advantages of Segmentation in Operating System
Let us check some of the major advantages of segmentation in the operating system below.
- Segmentation divides a program into logical sections (e.g., code, data, stack), making it easier to manage and understand.
- Unlike paging, where fixed-size pages cause wasted memory (internal fragmentation), segmentation allocates only the required memory, minimizing waste.
- Each segment is allocated only as much space as it needs, reducing memory wastage.
- Each segment has separate access rights (e.g., code segment is read-only, data segment is read-write).
- Since segments are independent, they can be loaded, modified, or shared separately.
- Segmentation allows multiple processes to share common code (e.g., system libraries) while keeping separate data segments.
Challenges of Segmentation in Operating System
Apart from the many advantages, segmentation in the operating system also offers many challenges in the operating system below.
- Segmentation suffers from external fragmentation which prevents efficient allocation in the memory.
- It also leads to complex memory management where keeping track of segment sizes, locations and free memory gets complex.
- In paging, physical addresses are quickly mapped using a page table which slows down the access time.
- Some segments can overwrite adjacent segments which can cause frequent crashes and data corruption.
- Each process requires a Segment Table to store information about segment locations, access permissions, and sizes.
- Some CPU architectures and operating systems do not support segmentation natively.
- While segmentation improves security by isolating different segments, shared code segments (e.g., libraries) can create vulnerabilities if not properly protected.
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Segmentation in Operating System FAQs
Q1. What is Segmentation in operating system?
Ans: Segmentation in an Operating system is a process that divides memory into logical parts called segments and each segment is listed with a unique identifier called segment number.
Q2. What is the use of Segmentation in operating system?
Ans: The segmentation is used to locate the segment in the computer memory. It prevents one program from accessing the segment part of the other programs.
Q3. What is the best advantage of segmentation?
Ans: Segmentation is faster, flexible, and secure as compared to paging in operating system.
Q4. What is the importance of segmentation in operating system?
Ans: Segmentation in operating system is essential for efficient memory management and program execution. Before segmentation, a large program is treated as a single entity, making memory allocation rigid and less organized.
