Learn: What Registers Do (Big Picture)

Welcome!Welcome back! You've already learned about why the CPU is essential and how the fetch-decode-execute cycle works. Today, we'll dive deeper into an important part of the CPU: registers. Let's explore their role and why they're important!

What are Registers?Registers are small, fast storage areas inside the CPU. They temporarily hold data or instructions that the CPU is currently working on. Registers are essential because they allow the CPU to work quickly and efficiently.

Why are Registers Important?During the fetch-decode-execute cycle, the CPU needs to store certain values like memory addresses, instructions, or data. Registers help by providing a fast and accessible space for these values. This speeds up processing because registers are faster than other types of memory, like RAM.

Types of RegistersDifferent registers in the CPU have specific roles:Program Counter (PC) — Stores the memory address of the next instruction the CPU will fetch.Memory Address Register (MAR) — Holds the address of the memory location that the CPU is currently accessing.Memory Data Register (MDR) — Stores the actual data being fetched from or written to memory.Accumulator — Holds the results of calculations or logic operations performed by the CPU.

Program Counter (PC)The Program Counter (PC) is essential for keeping the CPU organised. It tells the CPU where to find the next instruction in memory during the fetch-decode-execute cycle. After fetching an instruction, the PC automatically updates to the address of the next instruction.

Memory Address Register (MAR) and Memory Data Register (MDR)The Memory Address Register (MAR) holds the address of the memory location the CPU wants to access. The Memory Data Register (MDR) stores the actual data fetched from memory or data that needs to be written to memory. Together, these registers help the CPU interact with the computer's memory.

AccumulatorThe Accumulator is used for storing intermediate results of calculations or logic operations performed by the CPU. For example, when adding two numbers, the accumulator holds the sum before the CPU moves to the next step.

Review Time!Great work! You've learned about registers and their roles in the CPU during the fetch-decode-execute cycle. Let's test your understanding with a few final questions.