Generally, a variety of control operations of entertainment devices such as video game machines are performed by using control apparatuses.  Therefore, a plurality of control buttons are provided on the control apparatuses and the user controls those buttons, thereby controlling the entertainment devices.  As an example, the user can control a character which is displayed on a television receiver. 
Conventionally, according to the thus-constructed control apparatuses, in many cases, cross-shaped or circular directional control buttons having are disposed at the front-left thereof and a plurality of multi-purpose buttons are disposed at the front-right thereof. 
The directional control buttons and the multipurpose buttons comprise a tactile switch or rubber switch.  Since the switch is tuned on/off, the character id moved in a digital manner or the state of the character is changed in a digital manner. 
As explained above, the conventional entertainment device has only a function for digitally changing the character which is displayed on the television receiver by using the directional control buttons or the multi-purpose buttons, and thereby has a disadvantage in that the motion of the character and changes thereof are not gradual and the appearance thereof is poor. 
In order to overcome this disadvantage, according to a manipulation device for a game machine disclosed in Japanese Patent Laid-Open (unexamined) No.  7-88252, it is possible to control a character which is displayed on a display screen of a television receiver in an analog manner by adding an analog-type input device which comprises a track ball or joystick etc.  Japanese Patent Laid-Open (unexamined) No.  11-90042 discloses another conventional art to which an analog-type input device is added. 
However, the analog-type input device which comprises the track ball or joystick, etc.  is quite different from that of the above-described directional control buttons or multi-purpose buttons in view of the operability.  Therefore, it is expected that it takes a long time for a user who is accustomed to using the directional control buttons or multi-purpose buttons to become practiced in the operation of the analog-type input device and that the amount of fun which the entertainment device inherently provides is cut by half.