A computer input system is provided for using a smart terminal as an input device to a computer. The method for the computer includes receiving from the smart terminal, input to the smart terminal from an electronic pen, wherein the input is received by the computer through a predetermined communication mode established between the computer and the smart terminal, identifying a foreground application of the computer, interpreting the input in association with the foreground application, converting the interpreted input to an input signal associated with the foreground application, and controlling the foreground application with the input signal, to execute an operation corresponding to the input signal, where the input signal is a keyboard or mouse input signal.