Address Space

Uniprogramming: one process at a time

Multiprogramming: multiple processes, when one waits, switch to another

AS: all memory a process can address

there’s a 1-1 mapping between process and address space

• OS isolates address spaces
• One process can’t access another’s address space
• Same pointer address in different processes point to different memory

Cooperating Processes

2 Models: Message Passing and Shared Memory

• Message passing
  • Pros: All sharing is explicit, there’s less chance for error
  • Cons: Overhead, data copying, cross protection domains
• Shared Memory
  • Pros: Performance. Only need to set up shared memory once, then access without crossing protection domains
  • Cons: things can change behind your back → error prone