What is the process in operating system

            What is the process in operating system

 An operating system executes a variety of programs:

Batch system – jobs

Time-shared systems – user programs or tasks

Textbook uses the terms job and process almost interchangeably

Process – a program in execution; process execution must progress in sequential fashion

Multiple parts

The program code, also called text section

Current activity including program counter, processor registers

Stack containing temporary data

Function parameters, return addresses, local variables

Data section containing global variables

Heap containing memory dynamically allocated during run time

As a process executes, it changes state
   new:  The process is being created

running:  Instructions are being executed

waiting:  The process is waiting for some event to occur

ready:  The process is waiting to be assigned to a processor

terminated:  The process has finished execution

 Process Control Block(PCB):

Information associated with each process also called task control block


Process state – new,running, waiting, etc

Program counter – location of instruction to next execute

CPU registers – contents of all process  center registers

CPU scheduling information- priorities, scheduling queue pointers

Memory-management information – memory allocated to the process

Accounting information – CPU used, clock time elapsed since start, time limits

I/O status information – I/O devices allocated to process, list of open files