8. A method of controlling a digital television, the method comprising: displaying, via a display unit, a keypad including a plurality of key buttons assigned with different alphabet characters, respectively; receiving, via a controller, a first selection of a first key button of the plurality of key buttons; inputting, via the controller, a first alphabet character assigned to the first key button in a text input box of the display unit; predicting, via the controller, a word that starts with the first alphabet character; generating, via the controller, a first sub key button assigned with a second alphabet character of the predicted word on the keypad, wherein the first sub key button is displayed at a location to adjoin the first key button on the keypad, the first sub key button partially overlapping a second key button neighboring to the first key button; receiving, via the controller, a second selection of the first sub key button; inputting, via the controller, the second alphabet character next to the first alphabet character in the text input box; and generating, via the controller, a second sub key button assigned with a third alphabet character of the predicted word, wherein the second sub key button is displayed at the same location as the first sub key button to adjoin the first key button on the keypad, the second sub key button partially overlapping the same second key button neighboring to the first key button.
8. A method of controlling a digital television, the method comprising: displaying, via a display unit, a keypad including a plurality of key buttons assigned with different alphabet characters, respectively; receiving, via a controller, a first selection of a first key button of the plurality of key buttons; inputting, via the controller, a first alphabet character assigned to the first key button in a text input box of the display unit; predicting, via the controller, a word that starts with the first alphabet character; generating, via the controller, a first sub key button assigned with a second alphabet character of the predicted word on the keypad, wherein the first sub key button is displayed at a location to adjoin the first key button on the keypad, the first sub key button partially overlapping a second key button neighboring to the first key button; receiving, via the controller, a second selection of the first sub key button; inputting, via the controller, the second alphabet character next to the first alphabet character in the text input box; and generating, via the controller, a second sub key button assigned with a third alphabet character of the predicted word, wherein the second sub key button is displayed at the same location as the first sub key button to adjoin the first key button on the keypad, the second sub key button partially overlapping the same second key button neighboring to the first key button. 9. The method of claim 8 , further comprising: displaying the first sub key button together with information about the predicted word on the display unit.