Operating System
Paging and Segmentation
Paging and Segmentation are two important memory management techniques used by Operating Systems to efficiently allocate memory and support smooth execution of multiple processes.
Both techniques solve memory management problems in different ways: Paging focuses on fixed-size blocks, while Segmentation focuses on logical program structure.
Paging
Paging divides memory into fixed-size blocks called frames, and processes into fixed-size blocks called pages.
- Pages are mapped to frames using a page table
- Eliminates external fragmentation
- Allows non-contiguous memory allocation
- Improves memory utilization
Paging Structure
Process Pages
Memory Frames
Segmentation
Segmentation divides a program into logical units such as functions, stacks, heap, data, and code segments.
- Each segment has a different size
- Based on logical view of the program
- Easy to protect and share segments
- More natural for programmer understanding
Segmentation Structure
Paging vs Segmentation
| Paging | Segmentation |
|---|---|
| Fixed-size blocks | Variable-size segments |
| No external fragmentation | May suffer external fragmentation |
| Hardware-based mapping | Logical/program-based view |
| Simple but less flexible | More flexible and meaningful |
Key Points
- Paging uses fixed-size memory blocks called pages and frames.
- Segmentation uses logical divisions of a program.
- Paging removes external fragmentation.
- Segmentation improves logical structure and protection.
- Modern systems often combine both techniques.
Summary
Paging and Segmentation are fundamental memory management techniques. Paging focuses on efficient memory utilization using fixed-size blocks, while segmentation focuses on logical organization of programs. Together, they help operating systems achieve efficient, flexible, and scalable memory management.
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Chapter VII: Paging and Segmentation
Deep-dive quiz on paging structure, segmentation types, address translation, and how both techniques compare and combine.