1. A computer system, comprising: a voice-recognition module, receiving an external voice signal via a microphone, and determining whether the external voice signal corresponds to an operation instruction; a shared memory, configured to store shared state information; a microcontroller, setting the shared state information according to the operation instruction when the external voice signal corresponds to the operation instruction; a power-management module, generating a power-management signal according to the shared state information in the shared memory; and a central processing unit, performing a processing operation corresponding to the operation instruction according to the shared state information in the shared memory when the power-management module issues the power-management signal.