Distinguish, differentiate, compare and explain what is the difference between Paging and Segmentation, Logical vs. Physical Address Spaces, and Internal vs. External Fragmentation. Operating Systems Guide.
Paging vs. Segmentation
| Feature |
Paging |
Segmentation |
| Block Size |
Fixed-size blocks (physical memory divided into frames; logical into pages). |
Variable-size blocks based on logical programming units (functions, arrays, stacks). |
| Programmer Visibility |
Completely invisible to the programmer; managed strictly by the OS and hardware MMU. |
Visible to the programmer; compiler breaks program into logical segments. |
| Hardware Translation |
Uses a Page Table (Page number + Offset). |
Uses a Segment Table (Segment base address + Segment limit/length). |
| Fragmentation Type |
Suffers from Internal Fragmentation (unused space in final page); zero external fragmentation. |
Suffers from External Fragmentation (scattered free memory blocks); zero internal fragmentation. |
Internal Fragmentation vs. External Fragmentation
| Parameter |
Internal Fragmentation |
External Fragmentation |
| Location of Wasted Space |
Occurs inside allocated memory blocks or pages. |
Occurs outside allocated partitions (in free space between processes). |
| Cause |
Process is assigned a fixed-size partition larger than requested data size. |
Dynamic memory allocation and deallocation leaves tiny non-contiguous holes. |
| Remedy / Solution |
Reduce page size or implement dynamic slab allocation. |
Memory Compaction, or implementing Paging / Virtual Memory. |
Logical Address Space vs. Physical Address Space
| Feature |
Logical (Virtual) Address Space |
Physical Address Space |
| Generation Source |
Generated directly by the CPU during program execution. |
Represents the actual hardwired electrical address lines on the physical RAM bus. |
| Translation |
Mapped by the Memory Management Unit (MMU) using base registers or page tables. |
Direct access to RAM capacitor storage locations. |
Tags:
