Which sequence describes the basic instruction execution cycle of a CPU?

Which sequence describes the basic instruction execution cycle of a CPU?

• A. Decode-fetch-execute
• B. Fetch-decode-execute
• C. Execute-fetch-decode
• D. Fetch-execute-decode

Answer: (B)

The basic instruction processing cycle starts by fetching the next instruction from memory, using the program counter to locate it. Once fetched, the instruction is decoded to understand what operation is required and which operands are involved. Finally, the CPU executes that operation, carrying out the arithmetic, memory access, or control action specified. This order makes sense because you must know what to do before you can perform it, and you must have an instruction to decode in order to determine the appropriate action. While real CPUs can overlap these steps through pipelining, the simple, foundational cycle is fetch, then decode, then execute.

The basic instruction processing cycle starts by fetching the next instruction from memory, using the program counter to locate it. Once fetched, the instruction is decoded to understand what operation is required and which operands are involved. Finally, the CPU executes that operation, carrying out the arithmetic, memory access, or control action specified.

This order makes sense because you must know what to do before you can perform it, and you must have an instruction to decode in order to determine the appropriate action. While real CPUs can overlap these steps through pipelining, the simple, foundational cycle is fetch, then decode, then execute.