Process States and the Process State Graph

 

 

Processes

-          a program in execution (simple definition)

-          a process is an active entity, while a program is a static entity

-          at most one process can be running on the CPU (or a single processor in a multiprocessor machine) at one time

 

Process States

-          Each process is in exactly one of the following states at each instant of time:

 

-          New:  The process is being created

-          Running:  Instructions are being executed.

-          Waiting:  The process is waiting for some event to occur (such as an I/O completion)

-          Ready:  The process is ready to execute, but it must wait to be assigned to the processor

-          Terminated:  The process has finished execution.

 

Process State Graph

-          The process state graph is a conceptual model of how a process can change states. 

-          It does not correspond directly to a data structure in the operating system. 

-          It shows the valid changes that can be made to the process state and when these changes are made.