Process State

The process state consist of everything necessary to resume the process execution if it is somehow put aside temporarily. The process state consists of at least following:

*)Code for the program.
*)Program's static data.
*)Program's dynamic data.
*)Program's procedure call stack.
*)Contents of general purpose registers.
*)Contents of program counter (PC)
*)Contents of program status word (PSW).
*)Operating Systems resource in use.

Process state:

A process goes through a series of discrete process states.
New State: The process being created.

Running State: A process is said to be running if it has the CPU, that is, process actually using the CPU at that particular instant.

Blocked (or waiting) State: A process is said to be blocked if it is waiting for some event to happen such that as an I/O completion before it can proceed. Note that a process is unable to run until some external event happens.

Ready State: A process is said to be ready if it use a CPU if one were available. A ready state process is runable but temporarily stopped running to let another process run.

Terminated state: The process has finished execution.


Process table

To keep track of all the processes that are running on the system. To do this, the operating system maintains a process table.

The process table is very simple data structure: It's a large array of structures. Each structure containts several pieces of data. Some of the
pieces of data associated with a process include:

*)The last values observed in the registers while the process was running.
*)The last value observed in the program counter while the process was running.
*)The state of the process (Is it ready to go?)
*)The current working directory of the process
*)The user ID of the user running the process