PROCESS

CONTROL BLOCK

WHAT IS PROCESS CONTROL BLOCK ?

PROCESS CONTROL BLOCK

Each & every process in the operating

system is represented by PROCESS CONTROL BLOCK

Process Control Block ~ Task Control

Block or Task Struct

WHAT EXACTLY IS PCB ?

Its is a data structure in the operating

system kernel containing the information

needed to manage a particular process.

The PCB is “ the manifestation(visible) of

a process in an operating system”

PROCESS CONTROL BLOCK (PCB)

PROCESS CONTROL BLOCK (PCB)PCB consist of following information~

Pointer.

Process state.

Process number.

Program counter.

CPU register.

CPU scheduling information.

Memory management information.

Accounting information.

I/O status information.

POINTER ~ Its contains the address of another

process which is present in the ready queue

PROCESS STATE ~ Its contains the information

about the state of the process i.e.,

NEW

READY

RUNNING

WAITING

HALTED

program COUNTER ~ The counter specifies

the address of the next instruction to be

executed.

CPU REGISTERS ~ The register vary in number

and type depending in the type of computer

architecture, they include:

Accumulators, index register, stack pointer and

general purpose registers

CPU SHEDULING INFORMATION ~ This

information includes

Process priority

Pointer to scheduling queues

Other scheduling parameters.

MEMORY MANAGEMENT INFORMATION ~ This

information includes

Value of base and limit of registers

Page tables

Segment tables

Depending on the memory system used by the

operating system.

ACCOUNTING INFORMATION ~ This information includes

amount of CPU and real time used

time limit

account number

job or process number etc.

I/O STATUS INFORMATION ~ This information includes

list of I/O devices allocated to the process

list of open files etc.

Hence, the PCB serves as the repository for any information that may be vary from process to process.