An operating system executes a variety of programs:
1. Batch system – jobs
2. Time-shared systems – user programs or tasks
Textbook uses the terms job and process almost interchangeably.
Process – a program in execution; process execution must progress in sequential fashion.
A process includes:
1. program counter
3. data section
As a process executes, it changes state
1. new: The process is being created.
2. running: Instructions are being executed.
3. waiting: The process is waiting for some event to occur.
4. ready: The process is waiting to be assigned to a process.
5. terminated: The process has finished execution.
Diagram of Process State
Process Control Block (PCB)
Information associated with each process.
CPU scheduling information
I/O status information
CPU Switch From Process to Process