A system for fast, full-text entry for small electronic devices

A novel text entry system designed based on the ubiquitous 12-button telephone keypad and its adaptation for a soft keypad are presented. This system can be used to enter full text (letters + numbers + special characters) on devices where the number of keys or the keyboard area is limited. Letter-frequency data is used for assigning letters to the positions of a 3x3 matrix on keys, enhancing the entry of the most frequent Letters performed by a double-click. Less frequent letters and characters are entered based on a 3x3 adjacency matrix using an unambiguous, two-keystroke scheme. The same technique is applied to a virtual or soft keyboard layout so letters and characters are entered with taps or slides on an 11-button keypad. Based on the application of Fitts' law, this system is determined to be 67% faster than the QWERTY soft keyboard and 31% faster than the multi-tap text entry system commonly used on cell phones today. The system presented in this paper is implemented and runs on Palm OS PDAs, replacing the built-in QWERTY keyboard and Graffiti recognition systems of these PDAs.