Each process may be in one of the following states:

1.new.  The process is being created.

2.running. Instructions are being executed.

3.waiting.  The process is waiting for some event to occur (such as an I/O completion or reception of a signal) .

4.ready.  The process is waiting to be assigned to a processor.

5.terminated.  The process has finished execution.

      Process Control Block is a data structure in the operating system kernel containing the information needed to manage the scheduling of a particular process. The PCB is \"the manifestation of a process in an operating system.\"

      The role of the PCBs is central in process management: they are accessed and/or modified by most OS utilities, including those involved with scheduling, memory and I/O resource access and performance monitoring. It can be said that the set of the PCBs defines the current state of the operating system. Data structuring for processes is often done in terms of PCBs. For example, pointers to other PCBs inside a PCB allow the creation of those queues of processes in various scheduling states that was previously mentioned.