Which statement describes the CPU instruction cycle?

Which statement describes the CPU instruction cycle?

• A. An instruction cycle includes fetch, decode, execute, and write-back.
• B. An instruction cycle includes load, store, process.
• C. An instruction cycle includes compile, run, exit.
• D. An instruction cycle includes input, compute, output, reset.

Answer: (A)

Understanding the CPU instruction cycle means picturing how a processor handles a single instruction step by step. The cycle starts by fetching the next instruction from memory, using the program counter to know where to look, then decoding it so the control unit understands what operation to perform and which operands are involved. Next comes execution, where the actual operation is carried out (such as calculating a result or moving data), and finally write-back, where the result is stored back into a register or memory. This fetch-decode-execute-write-back sequence is the pattern that drives every instruction the CPU processes, enabling it to move on to the next one. That description matches the described process, while the other options refer to different activities: loading and storing are parts of memory access rather than the full per-instruction cycle; compiling, running, and exiting relate to software execution steps outside the CPU’s instruction cycle; and input, compute, output, and reset describe broader data flow or control actions rather than the per-instruction sequence. For a concrete example, consider adding two numbers: fetch the add instruction, decode it to see it’s an addition with two operands, execute the addition, and write the sum back to a register.