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,

Watch this Video Lecture

 

Next Article- Schedulers in OS

 

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