Learn: The Fetch-Decode-Execute Cycle

Welcome!You've already learned why the CPU is essential to a computer. Now, let's dive into how it processes instructions using the fetch-decode-execute cycle. This is a crucial process that enables the CPU to perform tasks.

What is the Fetch-Decode-Execute Cycle?The fetch-decode-execute cycle is the process the CPU follows to retrieve, understand, and act on instructions. It consists of three main steps: fetching the instruction, decoding what it means, and executing it. This cycle happens billions of times per second in modern CPUs.

Step 1: FetchIn the fetch step, the CPU retrieves the next instruction from memory. The Program Counter (PC) holds the address of the next instruction, and this address is sent to the Memory Address Register (MAR). The instruction is then fetched into the Memory Data Register (MDR).

Step 2: DecodeOnce the instruction has been fetched, the CPU decodes it in the Control Unit (CU). The CU translates the instruction into signals that the CPU can understand. This step ensures the CPU knows what operation to perform next.

Step 3: ExecuteIn the execute step, the CPU carries out the decoded instruction. For example, it might perform a calculation in the Arithmetic Logic Unit (ALU), move data between registers, or interact with memory. This is where the actual task happens.

The Role of RegistersRegisters are small, fast storage areas inside the CPU. Key registers include:Program Counter (PC): Holds the address of the next instruction.Memory Address Register (MAR): Stores the address of the data or instruction in memory.Memory Data Register (MDR): Holds the actual data or instruction fetched from memory.Accumulator: Stores intermediate results of calculations.

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

Well Done!You've completed the lesson on the fetch-decode-execute cycle. This process is essential to understanding how the CPU operates. Keep practising to solidify your knowledge!