A method and apparatus for managing computer storage devices and updating code in a computing system. The interface receives the identification information of a user-designated sheet sent from a first terminal and the position information of the first terminal. The voltage detector switches the first charging path to turn on the first switch, when the voltage value of the power storage unit 30 is lower than the threshold voltage, the power source can charge the power storage unit by the first switch, wherein the current limiting device limits the current value of first charging path to lower than a predetermined.