Many complex components come together to make a computer system work seamlessly. One such essential element is the program counter. There is a register in a PC (program counter) processor that contains the address of the next instruction to be executed from memory.
In this article we learn what program counter is, how it works and many more. So, let’s start –
Before going to the direct topic, let us discuss some primary terminologies such as:
CPU (Central Processing Unit)
The full name of the CPU is Central Processing Unit. It is also known as a processor. CPU is the brain of the computer system.
It is an electronic microchip that processes the data and converts it into useful information based on the instructions given and controls all the functions of the computer system.
Instructions
Computer instructions are a group of machine language instructions and they are executed by a specific computer processor. Whatever instruction we give to the computer, it will work on its basis.
Memory
Computer memory is a device that is used to store data and information. In other words, “Computer memory is an important part of the computer in which data is stored, without memory the computer does not work.” .Memory includes RAM and ROM.
What is Program Counter?
There is a register in a PC (program counter) processor that contains the address of the next instruction to be executed from memory.
It is a 16-bit register and is also called instruction counter, instruction pointer, and instruction address register (IAR). PC (program counter) is a digital counter that is needed to execute tasks quickly and track the current execution point.
All the instructions and data present in memory have a special address. As each instruction is processed, the program counter is updated to the address of the next instruction to be fetched. When a byte (machine code) is fetched, the PC is incremented by one. So that it can fetch the next instruction. If the computer is reset or restarted, the program counter returns to zero value.
For example, suppose the content of the PC is 8000H. This means that the processor wants to fetch the instruction byte on 8000H. After fetching the byte at 8000H, the PC automatically increments by one (1). In this way, the processor becomes ready to fetch the next byte of the instruction or to fetch the next opcode.
FAQs on Program Counter
Q.1: Can the program counter be modified?
Answer:
Yes, the program counter can be modified by certain instructions or events during program execution(prosecution). For illustration, raying instructions can change the program counter to deflect the inflow of prosecution to a different part of the program.
Q.2: What happens when the program counter is modified?
Answer:
When the program counter is modified, the central processing unit( CPU) will cost the instruction from the new address specified by the modified program counter. This allows for non-sequential execution(prosecution) and enables features like circles, conditionals, and function calls in programming languages.
Q.3: Is the program counter the same as a memory address?
Answer:
No , The program counter points to the coming instruction to be executed, whereas a memory address refers to a specific position in memory where data or instructions are stored.
Q.4: Can the program counter go backwards?
Answer:
In utmost cases, the program counter moves forward in a successful manner. still, there are certain instructions, similar as circles or jumps, that can beget the program counter to move backward or to a different position in memory.
Q.5: What happens if the program counter points to an invalid address?
Answer:
still, it can lead to a program crash or an error, If the program counter points to an invalid address. The central processing unit( CPU) may essay to cost an instruction from an invalid memory position, performing in undetermined behavior or an exception.