User Input

The trouble with miniaturization is that input can be difficult without a proper keyboard. This has been a problem for PDAs ever since they first appeared, and it gets worse as devices become smaller. A typical mobile phone may have no more than 12 small buttons, while tablet-sized devices may have none at all. Mice are even harder to implement without a desk to roll them over, so even laptops large enough to accommodate a comfortable keyboard usually rely on touch-sensitive pads or small sticks instead.

Keyboards

The keys on a full-size, typewriter-style board measure 19 mm square and can be pressed down at least 3 mm, shown in Figure 10.2. This means that the keyboard needs to be at least 200 mm wide for the Qwerty layout alone, and more if function keys are included. Most PDAs and all mobile phones are substantially smaller than this.

All clamshell PDAs include their own built-in keyboard, though there is always a trade-off between usability and portability. The big Jupiter-class Windows CE subnotebooks do have room for a real keyboard, but smaller devices have to compromise. A few manufacturers, such as Psion, have developed fold-out keyboards, which can be slightly larger than the device itself. Psion's largest model so far is the Series 7, which has fairly usable keys measuring 17 mm square.

Tablet PDAs and phones with larger screens sometimes offer a virtual keyboard, so that the user can type on a touch-sensitive screen. A less awkward solution is an external plug-in keyboard. Palm Computing has a full-size keyboard that folds into four, making it the same shape as the Palm device itself—though slightly thicker and heavier. Ericsson's Chatboard plugs into many of its mobile phones, but uses calculator-style keys and isn't foldable, though it's still an improvement on a phone's keypad.

Predictive Text Input

Entering text on a mobile phone's keypad can be a difficult and laborious task. To make it simpler, many companies implement a system known as Predictive Text Input. The most common is T9, and is licensed from AOL subsidiary Tegic Communications by all the major phone manufacturers.

T9 technology was first developed in 1987 as a communication system to aid people with disabilities. Using a specially engineered pair of glasses, a person could "type" text using his or her eye movements. The major obstacle to developing such a system was that the human eye can target only eight clear areas, and the computer processing needed to be quick. T9's inventors solved these problems by grouping letters onto fewer target areas and by creating a compressed linguistic database that recognizes commonly used words. In 1995, the T9 team realized that their target groups of letters corresponded to the keypad of a phone, which also uses eight keys to represent every letter of the alphabet, as shown in Figure 10.3.

Under the T9 system, users only need to press each button once, even though it could represent up to four different letters. The phone compares the key presses with its own dictionary to work out which word is being typed. Where more than one is possible, it presents a choice, with the most likely highlighted.

For example, the key sequence 263 could represent 27 different combinations of three letters, but only two of them actually correspond to English words: and and cod. The first of these is most commonly used, so this would be the default.

T9 has become particularly popular in Europe, even though Europeans are not used to phones with letters on the keys. Most fixed-line phones in Europe still show only numbers, and no telephone numbers are advertised as words.

Handwriting Recognition

Because tablets lack a keyboard, they need to incorporate some kind of handwriting recognition. This is notoriously difficult because everyone's writing is slightly different. Even the advanced mainframe computers used by post offices to sort mail have problems reading some people's writing, and the limited power of a PDA makes the problem much worse.

Nonetheless, handwriting recognition is making great progress. It improves with every version of Windows CE and has got to the stage where people can use it for serious note-taking. With an "autocorrect" feature in most Microsoft programs, many users find that they rarely need to make corrections—provided that they write carefully.

To get round the difficulty of trying to recognize everybody's scrawl, Palm OS devices use their own special code called Grafitti. This is supposed to be easier to recognize than regular writing, and also faster for the user to scribble. Though learning what amounts to a special type of shorthand intimidates many users, most find it is surprisingly easy, as the code amounts to a simplified version of existing characters. Computer magazine reviewers regularly say that the Grafitti system is faster, easier, and more accurate than the natural handwriting recognition of Windows CE devices, though it still isn't perfect. Palm claims a maximum speed of only 30 words per minute, which is less than even many two-finger typists can manage.

For technophobes, the company Anato is producing the ultimate handwriting recognition device: an ordinary pen. It automatically senses the movements of the pen across paper and transmits them to a nearby PC using Bluetooth. The PC recognizes the characters and responds using synthesized speech, allowing the user to send email or access text-based Web sites without ever pressing a button or seeing a screen.

normal: Web Resources http://www.pdabuzz.com This site has discussion boards and daily news about all kinds of PDAs. http://www.geek.com/pdageek/ More daily news, plus reviews and tips for PDA users are featured on this site. http://www.the-gadgeteer.com News and reviews of PDAs, mobile phones, and other gadgets are available on this site. http://www.palmzone.com This weekly online magazine covers Palm and PocketPC devices. http://www.nearlymobile.com Aimed at beginners, this site introduces PDAs with a particular emphasis on the Palm Computing platform. (continued) http://3lib.ukonline.co.uk This is a frequently updated amateur site, dedicated to Psion and Palm devices. http://www.media.mit.edu/projects/wearable/ This site contains information about the wearable computer project, aimed at producing PDA-like devices that can be used while walking around or performing other tasks.