A process control block (PCB) is a data structure used by an operating system to store information about a specific process. The main functions of a PCB include:
1. Process identification: Each PCB contains a unique identifier for the process, such as a process ID.
2. Process state: The PCB stores the current state of the process, such as running, ready, or waiting.
3. Program counter: The PCB keeps track of the address of the next instruction to be executed by the process.
4. CPU registers: The PCB stores the values of CPU registers for the process, allowing the process to be paused and resumed without losing its state.
5. Process priority: The PCB may store the priority level of the process, which is used by the operating system to determine the order in which processes are executed.
6. Memory management information: The PCB contains information about the memory allocated to the process, such as the base and limit registers.
7. I/O status information: The PCB stores information about any I/O devices that the process is using, such as open files or network connections.
Overall, the PCB plays a crucial role in managing and controlling processes within an operating system, allowing the system to efficiently schedule and execute multiple processes concurrently.