Learn: Program Counter - Tracking the Next Instruction

Welcome!You've already learned about registers like the MAR, MDR, and Accumulator, and how they support the fetch-decode-execute cycle. Now, let's dive deeper into the Program Counter (PC) and its role in tracking the next instruction.

What is the Program Counter?The Program Counter (PC) is a register in the CPU that stores the address of the next instruction to be fetched. It ensures the CPU knows where to look next in memory, keeping the sequence of instructions organised.

Why is the Program Counter important?The PC is essential because it allows the CPU to execute instructions in the correct order. Without it, the system wouldn't know which instruction to process next, leading to chaos in program execution.

How does the Program Counter work?During the fetch-decode-execute cycle, the PC provides the memory address of the next instruction to be fetched. After the CPU fetches the instruction, the PC is updated to point to the address of the following instruction.

Updating the Program CounterAfter fetching an instruction, the PC is incremented to point to the next instruction in memory. This process ensures instructions are executed sequentially, unless a jump or branch occurs, which updates the PC directly to a new address.

Branching and the Program CounterSometimes instructions involve branching, where the program jumps to a new address instead of incrementing sequentially. In this case, the PC is directly updated to the specified address, allowing conditional or looped execution.

Review Time!Great work! You've learned about the Program Counter's role in tracking instructions, updating sequentially, and handling branching. Let's test your understanding with a few questions.