up:: Fundamentals of Operating Systems prev:: Chapter 8 – Physical Memory & DRAM next:: Chapter 10 – Paging, Page Tables & Swap

Chapter 9 – Virtual Memory

Core idea

Each process sees its own private address space, regardless of physical memory layout.

Why virtual memory exists

• Solves fragmentation
• Provides process isolation
• Allows large programs to run
• Enables sharing (code, libraries)

Paging

• Memory divided into pages (usually 4 KB)
• Virtual pages mapped to physical frames
• Mapping stored in page tables
• CPU uses MMU for translation

Benefits

• Same virtual address ≠ same physical address
• Code can be shared, data isolated

Exam angles

• Virtual ≠ physical memory
• Page tables are per process