Virtual Memory
Provides illusion of very large memory
- Sum of the memory of many jobs greater than physical memory
- Address space of each job larger than physical memory
Allows available (fast and expensive) physical memory to be well utilized.
Simplifies memory management: code and data movement, protection, ... (main reason today)
Exploits memory hierarchy to keep average access time low.
Involves at least two storage levels: main and secondary
Virtual Address -- address used by the programmer
Virtual Address Space -- collection of such addresses
Memory Address -- address in physical memory also known as “physical address” or “real address”