Learn: The Fetch-Decode-Execute Cycle

Welcome!You've already learned why the CPU is essential to a computer. Now, let's build on that by exploring how the CPU processes instructions using the fetch-decode-execute cycle.

What is the Fetch-Decode-Execute Cycle?The fetch-decode-execute cycle is the process the CPU follows to carry out instructions. It is repeated continuously to ensure the computer operates correctly. Each cycle involves fetching instructions, decoding them, and executing them.

Step 1: FetchThe CPU retrieves the next instruction from memory. The Program Counter (PC) stores the address of the next instruction, while the Memory Address Register (MAR) sends the location to memory. The instruction is then loaded into the Memory Data Register (MDR).

Step 2: DecodeOnce the instruction is fetched, the Control Unit (CU) decodes it. The CU interprets the instruction and determines what actions are required, such as arithmetic operations or data transfers.

Step 3: ExecuteFinally, the CPU carries out the decoded instruction. The Arithmetic Logic Unit (ALU) performs calculations or logical operations, and results are stored in the Accumulator. If data needs to be moved, the CU coordinates this.

How Does This Cycle Keep Running?The CPU repeats this cycle continuously while the computer is on. By doing so, it ensures that all instructions in a program are processed in sequence, enabling the computer to function smoothly.

Review Time!Great work! Let's review what you've learned about the fetch-decode-execute cycle with a few questions.