A method to use a user interface includes when the user grips the apparatus in a standard shape, the controller identifies the griping fingers, perceives a commanded function based on the operations of the identified fingers, and executes the perceived function. Thus, a desired application or application function can be easily and quickly executed only by the operation of the fingers even when the handheld device is put in a bag or pocket, or when the user cannot check or handle the screen and buttons of the handheld device because the user is talking on the phone or in conference.