The Optimal Size of Handwriting Character Input Boxes on PDAs

Abstract

This article presents an empirical study to determine the optimal size of a box for the input of handwriting characters on personal digital assistants (PDAs). The experiments involve the consideration of boxes for different kinds of characters, different box sizes and shapes (square and rectangular), different user postures, and the age differences of users. The results are assessed in terms of high performance (high character recognition rates, minimal stroke protrusions outside the character box, minimal number of error corrections, minimum writing time) and subjective ratings (e.g., ease of writing and minimum degree of fatigue). The results show that the optimal size of character boxes for the input of alphanumeric characters is 12 × 14 mm (rectangular), whereas for Kanji (Chinese characters) mixed with Kana characters and for Hiragana & Katakana characters the optimal size is 14 × 14 mm (square). We believe that knowledge of the optimal size of character input boxes will be useful for the design of user interfaces on PDAs.