High Hopes-September 1998

The one-row keypad was seen as a very promising input method. Many potential benefits were identified:

  • Small size. Containing only a few keys arranged economically in a single row, the keyboard occupies very little space. The keys can be placed along the display edge, making the whole device only a little larger than the display.

  • Easy to learn. Most people know the mobile phone keypad layout. Since the character grouping (2abc, 3def, etc.) is retained, the one-row keyboard layout would be comfortable for these users. The alphabetic order of characters is also familiar.

  • Fast two-hand input. Although the one-row keyboard works to some extent with one hand, its benefits are most obvious when it is placed on a table or other flat surface. In these cases, the keypad can readily be operated with two hands. Even touch-typing would be possible!

  • Advantages over touch-screen input methods. Although devices with a one-row keyboard could also incorporate touch screens, physical push buttons have clear benefits. The keys provide an immediate tactile feedback, and can be easily used with the fingers, not requiring users to carry and find a stylus. Most touch screens can also be used with fingers, but less easily, and grease in the skin smudges the display.

  • Softkey benefits. Having the key label on the screen makes it possible to change the key function when needed. This creates flexibility in the user interface. It also makes text input easier, since the key labels are never covered by the user's fingers.

It was the last benefit, the flexibility of the softkey solution, that motivated the team to design a whole new user interface (UI) concept around the one-row keyboard. The concept included a relatively large touch screen. Text and data entry could be done either via the touch screen or the one-row keyboard, or both. In situations where the one-row keys were not needed for text entry, they remained functional as, for example, shortcuts to frequently used functions.

Preliminary usability testing was carried out with the new user interface using paper prototypes, and the results were encouraging. Besides the benefits mentioned above, some risks were also identified. For example, some team members came away with doubts about how easily the new layout could be learned. The risks were seen as small, though, compared with the long list of potential benefits, and the team was still excited about the idea.

From the very beginning, it was obvious that the width of the keyboard would be critical to the success of the whole concept. In a phone keypad, there are 15 keys that are used for text entry (the number keys 0 to 9, *, #, clear, and space, plus two arrow keys for moving the cursor). As the new keyboard was targeted primarily at touch-typing, the optimal key spacing would be about 19 mm (3⁄4 in), the measure typically used in full-size desktop keyboards. With 15 keys in a row, this spacing would increase the total width to 285 mm (111⁄4 in), which is clearly too large for a mobile, pocketable device. [The largest contemporary mobile phones were around 150 mm (6 in) long at the time.]

The team decided to cut out some keys; only the most important functions would now have dedicated keys. Less frequent functions such as symbol input could be removed from the keyboard and operated using the touch screen. It was decided that space and clear keys should be retained, based on their frequency of use and importance. The so-called next function of T9, which brings up the next most probable word match, was combined with the space key, such that pressing space repeatedly would scroll down the list of matches. These modifications cut the number of keys to 10. Still, with full 19-mm key spacing the keyboard was too wide. The hardware engineer of the group acquired several keyboards with different reduced key spacings for informal trials and comparisons. Finally, the team settled on 16 mm (5⁄8 in) key spacing. With these design changes, the width of the keyboard was reduced from the initial 285 mm (111⁄4 in) down to 160 mm (61⁄4 in). The size was regarded as a compromise. Touch-typing is not very convenient with key-spacing this narrow, especially for large fingers. On the other hand, total width was still quite large for a mobile keyboard. However, the compromise was good enough to begin user tests.

To facilitate the tests, a quick prototype was constructed. An old Toshiba 610 CT notebook computer was modified for the purpose. The function keys F1 to F10 were allocated as the 10 keys of the one-row keyboard (see Figure 7.3). All other keys were removed. Pieces of paper were pasted above the keys to present the labels. The prototype was kept very simple, taking less than a day to build. It was reasonably good for the first prototype nonetheless, and key spacing matched the required 16 mm exactly. In a matter of days, the programmer in the project was able to come up with a simple Windows text entry demo for the prototype. We were now ready to face the reactions of the users.

click to expand
Figure 7.3: The first one-row prototype. The keypad is designed for touch-typing, having a 16-mm key pitch. The total width of the keypad is 160 mm.



Mobile Usability(c) How Nokia Changed the Face of the Mobile Phone
Mobile Usability: How Nokia Changed the Face of the Mobile Phone
ISBN: 0071385142
EAN: 2147483647
Year: 2005
Pages: 142

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