Learn: The Fetch-Decode-Execute Cycle

Welcome!Building on your understanding of why the CPU is essential, we will now explore the fetch-decode-execute cycle, a key process that allows the CPU to execute instructions.

What is the Fetch-Decode-Execute Cycle?The fetch-decode-execute cycle is the process the CPU uses to retrieve, understand, and carry out instructions. It ensures that the computer operates correctly and efficiently by following this repeating process for every instruction.

Step 1: FetchDuring the fetch stage, the CPU retrieves the instruction from memory. The Program Counter (PC) holds the memory address of the next instruction, and the Memory Address Register (MAR) is used to access that memory location. The data is then copied into the Memory Data Register (MDR).

Step 2: DecodeIn the decode stage, the CPU uses the Control Unit (CU) to interpret the fetched instruction. It checks the opcode (operation code) to understand what action needs to be performed and identifies the required operands (data or addresses).

Step 3: ExecuteIn the execute stage, the CPU carries out the decoded instruction. This often involves the Arithmetic Logic Unit (ALU), which performs calculations or logical operations. Results are stored in the Accumulator (ACC) or other registers.

How These Steps Work TogetherThe fetch-decode-execute cycle repeats continuously to process instructions in sequence. This cycle allows the CPU to carry out tasks efficiently, whether it’s running software, performing calculations, or managing data.

Review Time!Great work! You've learned about the fetch-decode-execute cycle and the roles of key components. Let's test your understanding with a few review questions.