Learn: The Fetch-Decode-Execute Cycle

Welcome!Building on what you've already learned about why the CPU is essential, today we'll explore how it processes instructions using the Fetch-Decode-Execute Cycle. This is a key concept for understanding how computers work!

What is the Fetch-Decode-Execute Cycle?The Fetch-Decode-Execute Cycle is the process the CPU uses to carry out instructions. It involves fetching the instruction from memory, decoding what it means, and executing it. This cycle happens repeatedly and very quickly to run programs.

Step 1: FetchThe CPU fetches the next instruction from memory. The Program Counter (PC) holds the address of this instruction, and the Memory Address Register (MAR) sends this address to memory. The instruction is then copied into the Memory Data Register (MDR).

Step 2: DecodeOnce the instruction is fetched, the Control Unit (CU) decodes it to understand what needs to be done. It identifies the operation and any data involved. This step ensures the CPU knows how to execute the instruction.

Step 3: ExecuteDuring execution, the CPU carries out the decoded instruction. This might involve performing a calculation in the Arithmetic Logic Unit (ALU), moving data, or interacting with memory. The result may be stored in the Accumulator.

How Registers Work TogetherRegisters are small, fast storage areas in the CPU. They include the Program Counter, Memory Address Register, Memory Data Register, and Accumulator. Each has a specific role in the cycle.

Review Time!Great work! You've learned how the Fetch-Decode-Execute Cycle works and how the CPU components interact. Let's test your understanding with a few questions.