Arizona State University (ASU) CSE100 Principles of Programming with C++ Midterm 1 Practice Exam

The decode phase in a CPU cycle is crucial as it translates the fetched instruction into control signals that the CPU can understand and act upon. During this phase, the instruction fetched from memory, which is typically in binary form, is interpreted by the control unit of the CPU. The control unit decodes the instruction to determine what operation needs to be performed (e.g., ADD, SUBTRACT, LOAD, STORE) and identifies the operands involved. This translation into signals allows the appropriate circuits within the CPU to execute the desired operation during the subsequent execution phase.

The other choices focus on different aspects of the CPU cycle. Executing the instruction pertains to the actual operation after the decode phase, and retrieving the instruction involves accessing memory to get the instruction before it is decoded. Storing the result of the instruction is part of the later stages in the cycle, specifically after execution, when any calculated result needs to be saved in memory or registers. Understanding the decode phase as the point of translation into actionable signals is essential for grasping how a CPU processes instructions efficiently.