1. A method for a method for inputting different characters by multi-directionally pressing one of a plurality of keys of a key pad of a portable electronic device more than one time, each key having a plurality of protuberances on an underside and a circuit board of the portable electronic device having a plurality of pads being equal in number to the protuberances and disposed correspondingly thereto, the method comprising: determining the conduction periods of time by a control circuit of the portable electronic device, while one key being multi-directionally pressed a plurality of times to cause the protuberances to contact the corresponding pads at different conduction periods of time; and reading a corresponding character sequentially from a built-in character database by a storage device of the portable electronic device based on a longer one of the conduction periods of time.