Program Counter
The program counter is a special-purpose register that keeps track of the address of the instruction that is to be executed next in a computer program. It is also known as the instruction pointer or simply the PC.

Function of Program Counter
The program counter is an essential component of the central processing unit (CPU) and plays a crucial role in the execution of instructions. It performs the following functions:

1. Sequential Execution: The program counter ensures the sequential execution of instructions in a program. It keeps track of the memory address of the next instruction, allowing the CPU to fetch the instruction from the memory and execute it.

2. Program Flow Control: The program counter is responsible for controlling the flow of the program. It determines the order in which instructions are executed by providing the address of the next instruction to be fetched and executed.

3. Branching and Jumping: In addition to sequential execution, the program counter also handles branching and jumping instructions. These instructions modify the program counter to redirect the flow of the program to a different memory address, enabling the execution of conditional statements, loops, and function calls.

4. Interrupt Handling: The program counter is involved in interrupt handling. When an interrupt occurs, the current address stored in the program counter is saved, and the program counter is loaded with the address of the interrupt service routine. After the interrupt is serviced, the saved address is restored, and the program continues from where it left off.

5. Context Switching: During context switching in a multitasking environment, the program counter is saved along with other register values of the current process. When the process is resumed, the saved program counter is loaded, allowing the program to continue execution from the point at which it was interrupted.

Conclusion
The program counter is a crucial special-purpose register that keeps track of the address of the instruction to be executed next in a computer program. It ensures the sequential execution of instructions, controls the program flow, handles branching and jumping, and plays a role in interrupt handling and context switching.