User can input characters and numerals without mode transition on a keypad using Part-Whole Selection (PWSM). Moreover, by allocating characters having higher use frequency to lattice elements on each button in the Order of Proximity to Base Lattice Element (OPBLE), input efficiency of the PWSM is maximized, and the number of times a button is pressed in the Base Repeat Selection Method (BRSM) is minimized. Applying Control Processing Method can simplify character arrangement on a keypad. For languages such as Korean, Hindi, Myanmar and the other languages in which consonants and vowels alternately come after each other, representative consonants and vowels are uniformly assigned to buttons on a keypad, thereby minimizing ambiguity when the RSM is used in input operation. Finally, representative consonants having phonetic values are allocated to Base Lattice Elements (BLEs) on each button, so that they can be used for memorizing or naming telephone numbers and a variety of codes.