Mobile phone, notifying method of key operation valid/invalid and its program

The present invention discloses a portable telephone, which is capable of easily and low power emit the input key is valid or invalid notice, without special hardware. If the power of the portable telephone set is turned on, and then key input is detected by the key sheet, the control key assignment portion of the reference information to distinguish whether or not the input key is valid. If the input key is valid, then the control section generates a first control speaker beeps, but if the inputted key is invalid, the control section generates a second control speaker beep is different from the first beep .