Learn: Fetch-Decode-Execute Cycle

Welcome!Today we'll learn about the Fetch-Decode-Execute (FDE) Cycle. This is how a computer processes instructions step by step. Let's explore how it works!

What is the Fetch-Decode-Execute Cycle?The FDE cycle is the process a CPU uses to retrieve and execute instructions. It involves three main stages: fetch (getting the instruction), decode (understanding it), and execute (carrying it out). This cycle repeats constantly while the computer is running.

Fetch StageDuring the fetch stage, the CPU retrieves an instruction from memory. It uses the Program Counter (PC) to identify the address of the instruction. The instruction is then loaded into the Memory Data Register (MDR).

Decode StageIn the decode stage, the CPU interprets the fetched instruction. The Current Instruction Register (CIR) holds the instruction while the Control Unit decodes it into signals that the CPU can understand.

Execute StageDuring the execute stage, the CPU carries out the decoded instruction. This might involve performing a calculation in the Arithmetic Logic Unit (ALU), moving data between registers, or interacting with input/output devices.

Registers in the FDE CycleSeveral registers play key roles in the FDE cycle: Program Counter (PC), Memory Address Register (MAR), Memory Data Register (MDR), and Current Instruction Register (CIR). Each has a specific job in processing instructions.

Review Time!Great work! You've learned about the Fetch-Decode-Execute cycle and the roles of registers. Let's test your understanding with a few final questions.