Process: Any
program running in computer is a process. So there can be multiple processes
running in same computer or there can be single process running. Each and every
process will have own flow of control. In sequential execution environment, all
the process are executed in sequentially. In multiprocessor environment all the
process are switched forth and back.
Each running process has own memory range where it has
executable program, data, & stack etc… , is called Address Space/Core Image. Each process is also associated with set
of program registers, counter; stack pointer and Hardware registers etc.
When a process (A) is suspended temporarily by processor and
later when it is resumed, it must be started from the exactly the place from
where it was suspended. To do so, whole state of the process is being stored in
a table called Process Table.
A process can create another process called child processes, these child processes
can further create another child processes, through this we can have process
hierarchy.
Process
Creation:
There are 4 principal events by which a process can be
created
- System
Initialization
- A process
creates another process
- A user
request to create another process
- Initializing
batch job.
Process
termination:
There are the following main reason due to which a process
can be terminated
- Normal Exit
- Error Exit
- Fatal Error
Exit
- Killed by
another Process.