Memory Management & Paging
The OS maps logical addresses to physical memory. Paging splits memory into fixed-size frames to remove external fragmentation.
Cheat sheet
- ▸Logical address = page number + offset; page table maps page → frame.
- ▸TLB caches recent page-table entries to speed translation.
- ▸Paging → no external fragmentation, small internal fragmentation.
- ▸Segmentation → variable-sized logical units, external fragmentation.
- ▸Allocation strategies: First fit, Best fit, Worst fit.
- ▸Effective Access Time = h×(TLB + mem) + (1−h)×(TLB + 2×mem).
Paging vs Segmentation
| Aspect | Paging | Segmentation |
|---|---|---|
| Unit size | Fixed (pages) | Variable (segments) |
| Fragmentation | Internal | External |
| Visible to programmer | No | Yes (code, stack, data) |
| Table | Page table | Segment table (base, limit) |
Visual
Logical addr [ page p | offset d ]
│
Page table[p] = frame f
▼
Physical addr [ frame f | offset d ]Top 10 campus interview questions
Quick quiz
1. Paging suffers from:
2. TLB is a:
3. Page size 4 KB → offset bits:
4. Segmentation causes:
5. Compaction solves: