Abstract: A method and an apparatus for controlling functionalities of a computer system are provided. The apparatus comprises a key, a serial input unit, and a processing unit. The key is used for enabling an adjustment function of a computer system. The serial input unit is used for generating an adjustment signal for modifying a parameter corresponding to the adjustment function. The adjustment signal is omni-directional and continuously variable. The processing unit connected to the key and the serial input unit is used for modifying the parameter according to the adjustment signal so as to execute the adjustment function when the adjustment function is enabled. As a result, a more intuitive way to control the computer system is provided so as to increase the convenience of using the computer system.