Curious to know the full form of the PC -Program counter/Personal computer? Check it out

PC refers to different full forms in several situations for example 

PC - Personal computer in a real-world scenario

PC -Program counter according to the programming world 

    Let's see more detailed aspects of PC as the program counter 

How to define a program counter(PC)?

       The program counter also known as the instruction pointer or simply PC is a fundamental component of a computer's CPU.

It is a special register that keeps track of the memory address of the Next instruction to be executed in a program.

Is PC a necessary register in every processor?

     Yes, of course, a PC is crucial because it allows the CPU to fetch instructions from memory in a sequential manner, By keeping track of current instructions address, the PC ensures that the CPU knows which instruction to fetch next. 

  Sometimes the program counter is called the Sequence control register (SCR) as the control unit uses its contents to control the sequence of instruction execution.

A Glance at what register means?

      A register is one of a small set of data-holding places that are part of the computer processor. It may hold a computer instruction, a storage address, or any kind of data. It is a quickly accessible location available to a CPU that is used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU.

How does the PC interact with interrupts? 

    Interrupts are events that occur asynchronously during program execution, often triggered by external devices. When an interrupt occurs, the PC is temporarily saved and the CPU jumps to an interrupt handler routine. After handling an interrupt, the PC is restored to its original value, allowing the interrupted program to continue execution.

Does PC ever go backward while working on a procedure?

     In almost 80% of cases, the PC moves forward sequentially, however, there are certain instructions such as loops or jumps that can cause the PC to move backward or to a different location in memory.

Behalf of the PC (Program counter)  Do u need IR(Instruction register)

       You will need both always. The program counter (PC) holds the address of the next instruction to be executed, while the instruction register (IR) holds the encoded instruction. Upon fetching the instruction, the program counter is incremented by one "address value" (to the location of the next instruction). The instruction is then decoded and executed appropriately.

 

The reason why you need both is that if you only had a program counter and used it for both purposes you would get the following troublesome system:

[Beginning of program execution]

•PC contains 0x00000000 (say this is the start address of the program in memory)

•Encoded instruction is fetched from the memory and placed into the PC.

•The instruction is decoded and executed.

Now it is time to move on to the next instruction so we go back to the PC to see what the address of the next instruction is. However, we have a problem because PC's previous address was removed so we have no idea where the next instruction is.

Therefore, we need another register to hold the actual instruction fetched from memory. Once we fetch that memory, we increase the PC so that we know where to fetch the next instruction.

P.S. The width of the registers varies depending on the architecture's word size.

 For example, for a 32-bit processor, the word size is 32-bit. Therefore, the registers on the CPU would be 32 bits. 

Instruction registers are no different in dimensions. The difference is in the behavior and interpretation. Instructions are encoded in various forms, however, they still occupy a 32-bit register. For example, the Nios II processor from Altera contains 3 different instruction types, each encoded differently.

The Main purpose of the Program counter(PC)

The purpose of the program counter is to:

•Count the total number of programs that have been processed.

•Hold the address of the next instruction to be executed.

•Hold the address at the top of the run-time stack.

•Count the total number of instructions that have been executed in a program.

Conclusion 

     In summary, the program counter is a key component in computer architecture that enables the CPU to execute instructions in the correct sequence. It ensures the smooth and orderly operation of computer programs, and facilitates jumps, branches, interrupts, and subroutine calls.