Which statement best describes the Execute stage of the FDE cycle?

• A. The instruction is decoded by the CU.
• B. The next MAR/MDR values are loaded.
• C. The instruction is performed, such as memory access, computation, or altering the program counter.
• D. The program counter is reset to zero.

Answer: (C)

The Execute stage is where the CPU applies the instruction’s effect to the machine state. After decoding, the processor carries out the operation: the ALU performs arithmetic or logical calculations, memory is read or written, and the program counter is updated to alter the flow of execution (for example, when a branch or jump is taken). In other words, this stage actually performs the instruction. For instance, an add instruction makes the ALU compute a sum, a load instruction fetches data from memory, and a branch instruction changes the next instruction by adjusting the program counter. The other options describe earlier steps or unusual reset behavior: decoding happens in the decode step, loading MAR/MDR relates to memory fetch, and resetting the PC to zero is not a normal operation during ordinary execution.