Process Control Block in OS

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process control block diagram in operating system, process block
Process Control Block

A Process Control Block also called PCB in an operating system. Each process is represented in the operating system by its own PCB. A PCB is a data block. It consists of all information of a special process.


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What is PCB?

The PCB is a central store of information that allows the operating system to locate all the key information about the process. The operating system uses this information and performs the operations in the process. The operations include suspending a process, resuming a process, change the process priority, dispatch a process, name the process and so on.

Process Termination

The process terminates from the running state includes so many causes. Generally, the process terminates when execution is finished. Some other causes are-

  1. Time slot expired
  2. Memory boundary violation
  3. Input/Output failure
  4. Parent termination
  5. Parent request
  6. Invalid instruction

Operations on Process

A system that manages process must be able to perform certain operations and with the process. These include 7 state process model.

  1. Create a process
  2. Destroy a process
  3. Resume a process(Restart the process)
  4. change the priority of a process
  5. Block of process
  6. wake up a process
  7. Enable a process to communicate with other processes

Changing the priority of the process involves nothing more than modifying the priority value in the PCB. The operation resumes a process means to submit the process from "suspended" state to ready state.

Process Creation

Concurrent Process

Two processes are ‘serial’ if the execution of one must be completed before the execution of other starts. If the two processes said to be concurrent, they are not serial, and their execution can overlap in time.

Concurrent Process Model
Concurrent Process

Here the example of a concurrent process in an operating system. Let's assume there are three process P1, P2 and P3 and execution time is T. According to the figure, the execution time of P1, P2, and P3 overlapped, so these called concurrent process model.

I hope you have cleared about A Process Control Block in the operating system.