Five-State Process Model States

As a process executes, it changes state. The state of a process is defined in part by the current activity of that process. A process may be in one of the following states:

Running: The currently executing process.

Waiting/Blocked: Process waiting for some event such as completion of I/O operation, waiting for other processes, synchronization signal, etc.

Ready: A process that is waiting to be executed.

New: The process that is just being created. The Program Control Block is already being made but the program is not yet loaded in the main memory. The program remains in the new state until the long-term scheduler moves the process to the ready state (main memory).

Terminated/Exit: A process that is finished or aborted due to some reason.

These names are arbitrary, and they vary across operating systems. The states that they represent are found on all systems, however. Certain operating systems also more finely delineate process states. It is important to realize that only one process can be running on any processor at any instant. Many processes may be ready and waiting, however. The state diagram corresponding to these states is presented in Figure.