Abstract: A method for controlling switch of input mode of keyboard instructions is to provide and load a program to intellectualize an auxiliary keypad without forcing any of or both the keypad and a main keyboard to retain at a specified state. In other words, the program of the keypad will read the present status flag of the keypad and the main keyboard and put them in memory. Hence, when an arbitrary key of the keypad is pressed, the program will compare whether the state of the keypad and the main keyboard are identical or not; if positive, a key code from the keypad is acceptable, otherwise, a Num Lock code will be transmitted to a host frame of a notebook computer for changing the state of the main keyboard into that of the keypad for receiving a key code from the keypad. After transmission of the key code to the host frame, the program will send the Num Lock code again to the host frame for restoring the state of the main keyboard while the keypad remains its state unchanged.