What is Process?

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.