Tag: Process Control Block

Process Control Block | Process Attributes

Process Control Block-


  • Process Control Block (PCB) is a data structure that stores information about a particular process.
  • This information is required by the CPU while executing the process.


The Process Control Block of a process looks like-



  • Each process is identified by its own process control block (PCB).
  • It is also called as context of the process.


Process Attributes-


The various attributes of process stored in the PCB are-


1. Process Id-


  • Process Id is a unique Id that identifies each process of the system uniquely.
  • A process Id is assigned to each process during its creation.


2. Program Counter-


  • Program counter specifies the address of the instruction to be executed next.
  • Before execution, program counter is initialized with the address of the first instruction of the program.
  • After executing an instruction, value of program counter is automatically incremented to point to the next instruction.
  • This process repeats till the end of the program.


3. Process State-


  • Each process goes through different states during its lifetime.
  • Process state specifies the current state of the process.


Read more- Process States in OS


4. Priority-


  • Priority specifies how urgent is to execute the process.
  • Process with the highest priority is allocated the CPU first among all the processes.


5. General Purpose Registers-


  • General purpose registers are used to hold the data of process generated during its execution.
  • Each process has its own set of registers which are maintained by its PCB.


6. List of Open Files-


  • Each process requires some files which must be present in the main memory during its execution.
  • PCB maintains a list of files used by the process during its execution.


7. List of Open Devices-


  • PCB maintains a list of open devices used by the process during its execution.


Important Notes-


  • PCB of each process resides in the main memory.
  • There exists only one PCB corresponding to each process.
  • PCB of all the processes are present in a linked list.


To gain better understanding about Process Control Block,

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Next Article- Schedulers in OS


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