A program in execution is called Process.The most central concept of operating system is the process. The term process was first introduce by Multics system in 1960s.
A program does not perform any task itself. However,when a program run on the computer it performs an action. Probably, the difference between process and program is process is active entity.While, program is static entity.
Processes in the operating system are in following states:
- New : The process is create.
- Ready: The process is waiting to be assign to a processor.
- Running: Instructions are execute.
- Waiting: The process is waiting for some event to occur(such as an I/O completion or reception of a signal).
- Terminate: The process finish execution.
Transition between process states
Actually the major states of the process are Block, Running,Ready and Terminated. Here, New state only describe the creation of process.
In this transition, when a new process is select by CPU scheduler. Then the process is send to the ready queue. After that,it is send for execution towards CPU.
This transition is made when a running process need some I/O operation.Then the process is send to block state.The process is also send to block state when there is a system call.
Here, this transition occurs when scheduler decides that the running process has use its time slice.Then the process is send to ready state again.
In this, the program after execution is terminate.when the process is complete successfully then it is terminated from the queue.
In this the process after getting its requirement like I/O operation it is send to ready state.