Learn: Program Counter - Tracking the Next Instruction

Welcome!Great to see you again! You've already learned a lot about how the CPU works, including the fetch-decode-execute cycle and the role of registers like the MAR and MDR. Today, we're diving into the Program Counter, an essential part of the CPU responsible for keeping track of what instruction needs to be executed next. Let's get started!

What is the Program Counter?The Program Counter (PC) is a register in the CPU that holds the memory address of the next instruction to be executed. This helps the CPU keep track of where it is in the sequence of program instructions, making sure it processes commands in the correct order.

How does the Program Counter work?During the fetch-decode-execute cycle, the Program Counter is checked to find the memory address of the next instruction. After the CPU fetches the instruction from memory, the Program Counter automatically updates to point to the address of the next instruction, ensuring a smooth flow of processing.

Why is the Program Counter important?The Program Counter ensures the sequence of instructions is followed correctly during program execution. Without it, the CPU wouldn't know which instruction to process next, leading to errors or inefficient execution.

How does the Program Counter interact with other registers?When the CPU starts executing instructions, the Program Counter sends the address of the next instruction to the Memory Address Register (MAR). The MAR uses this address to fetch the instruction from memory. After fetching, the Program Counter is incremented to point to the next instruction, ensuring the process continues seamlessly.

Incrementing the Program CounterAfter the CPU fetches an instruction, the Program Counter is incremented. This means its value increases by 1 so that it points to the address of the next instruction in memory. If the program includes a jump instruction, the Program Counter updates to a new address instead of incrementing.

Jump Instructions and the Program CounterSometimes, a program needs to jump to a specific instruction instead of following the sequence. This is where jump instructions come in. When a jump instruction is executed, the Program Counter is updated to a new address instead of incrementing, allowing the CPU to 'jump' to another part of the program.

Review Time!Great work so far! You've learned about the role of the Program Counter, its importance, and how it interacts with other registers. Now let's test your understanding with a few questions.

Well done!You've successfully completed the lesson on the Program Counter. Keep practising, and you'll master how the CPU tracks and executes instructions in no time!