- Virtual Machine
- hides complexity and limitations of hardware from application programmers
- Hiding Complexity
- advantages: simpler, no physical worries
- disadvantages: lack of control, false assumptions about black box
- General OS Functions
- screen display
- storage accesses
- coordination amond applications
- Coordination
- applications should not crash one another
- address space: memory addresses that an application can touch
- an application should not crash OS
- Operating System
- overcomes hardware
- protects from one another
- allocates resources
- Batch System
- collects a batch of jobs before processing
- Multiprocessing
- multiple programs can run concurrently
- Timeshare systems
- each user can afford to own terminals and interact with machines
- Multitasking
- a single user can run multiple programs on the same machine at the same time
- Multiprocessing