What does the Fetch Decode Execute cycle (FDE) do?

• A. It repeatedly fetches an instruction, decodes it, and executes it.
• B. It writes results to memory before decoding.
• C. It only fetches instructions but does not decode.
• D. It executes instructions without decoding.

Answer: (A)

This question tests how the CPU processes each instruction in a loop: fetch, decode, and execute. The processor reads an instruction from memory (fetch), analyzes its opcode and operands to determine what needs to be done (decode), and then performs the required operation using the ALU, registers, and memory (execute). This cycle repeats for every instruction, driving the flow of a program.

The described sequence is the only one that makes sense because you can’t know what to do without decoding the instruction, and you can’t perform the operation correctly without first decoding it. Simply writing results to memory before decoding would not know what to write, and executing without decoding or only fetching would skip or discard the actual work the instruction specifies.