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<Paper uid="C02-1149">
  <Title>Entering Text with A Four-Button Device</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Electronic machinery is becoming smaller;; recent developmentsin palmtop andmobile-phone technologies oer dramatic examples of this process. Since smaller machines are more portable, their users have freer access to information. Here, however, the user interface is a major issue.</Paragraph>
    <Paragraph position="1"> If a machine is being used as a medium for person-to-person communications, a natural interface might be speech-based. Forother tasks, however,like browsing through Internet pages or looking up databases, the most natural tool for control and data entry is still the keyboard.</Paragraph>
    <Paragraph position="2"> Mobile machines oer little surface space, so only a few buttons are available for the entry of text. The most representativeformistheuseof10keys for text entry on mobile phones. However, even smaller machines continue to appear, suchaswatch-sized computers. It might not be possible to equip such machines with more than four or ve buttons. Questions then arise. Is it possible to enter text with a small number of buttons? What about four buttons? How ecient can wemake this? Other potential applications for text entry with four buttons include the control panels of oce machines and household machines. Although these machines increasingly contain functions that allow access to the Internet, sucient surface space for a full keyboard is often not available. Another potential application is in text-entry interfaces for elderly and disabled people. A report (of Advanced Design of Integrated Information Society, 2000) indicates that keyboard operation is the highest hurdletotheuseof computers by the aged. The situation is even worse for people with hand-related disabilities. A text-entry device with four largebuttons might facilitate human-machine communications bysuch people.</Paragraph>
    <Paragraph position="3"> The idea of decreasing the number of keys on the keyboard in itself is not new. The oldest realization of this idea is the stenotype keyboards.</Paragraph>
    <Paragraph position="4"> With the recent popularity of mobile machines, researchers have become increasingly interested in onehanded keyboards(Mathias et al., 1996). Most of the work to date in this eld has been related to mobile phones. Text entry on current-generation devices remains cumbersome, so innovative companies(Tegic 9, 2000)(ZI-Corp., 2000)(Slangsoft, 2000) have proposed predictive methods for the more eciententry of text by implementing a method that had rst been proposed some years earlier(Rau and Skiena, 1994).</Paragraph>
    <Paragraph position="5"> The results of several studies have veried its eciency(James and Reischel, 2001)(Tanaka-Ishii et al., 2000), so the technology looks promising in the context of mobile phones.</Paragraph>
    <Paragraph position="6"> Our study goes further in decreasing the number of buttons than the above-cited studies. In our study, we tried various text-entry methods and found the predictive method to be the best. As far as we know, no other study that includes the application of a language model has yet been carried out in this context;; neither has the eciency of this approach been examined. Additionally, the major contribution is our study of the potential power of a language model by examining its actual eciency on a device with few buttons.</Paragraph>
    <Paragraph position="7"> In the next section, we rst show how text is entered via our TouchMeKey4 keypad.</Paragraph>
  </Section>
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