Abstract: A computer system used to execute an application includes a motion sensing unit, a processor and an instruction transfer unit. The motion sensing unit senses a gesture of a human body and generates an input instruction based on the gesture. The processor executes the application (or a game). The instruction transfer unit is connected with the motion sensing unit and the processor and serves as a communication interface between the motion sensing unit and the application. The instruction transfer unit transfers the input instruction to a control command, and the processor controls and executes the application in accordance with the control command.