WRITING anything on a palmtop computer can be both fiddly and exasperating. Now a new way of writing text that lets you build up sentences simply by steering the cursor through a landscape of letters promises to be faster and more accurate.
Even the clever software on today’s cellphones and PDAs, which guesses the word you’re writing, has problems, says David MacKay, a computer scientist at the University of Cambridge who has been developing the new approach. With the conventional software, you have to look at the screen to see if the word you want is there, and click on it before you can carry on. “That requires you to make a mental switch,” he says. MacKay and his colleague David Ward figured they could make writing much simpler if people could simply point at the characters they want to enter.
The software they came up with, which they’ve called Dasher, starts by displaying the letters of the alphabet in a column of squares on the right-hand side of the computer’s screen. Using the palmtop’s pen-like stylus, you drag the cursor from the centre of the screen towards the first letter you want to write. As the cursor approaches that square, it and its closest neighbours get larger, pushing other letters off the screen. Inside each of the growing boxes, Dasher displays another column of small boxes containing the letters most likely to follow the first letter, and on you go.
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To decide which letter sequences you are most likely to want, Dasher’s memory is loaded with a file of typical text. As you choose each new letter, the system searches this “training text” for the last five characters you selected and calculates which ones are most likely to follow. If you have written fewer than five letters, Dasher searches what’s available. If you make a mistake, you can move the cursor to the left of the screen to start the word again.
Using a mouse, MacKay reckons you could enter up to 34 words per minute. But he thinks Dasher will be particularly useful for people with little or no dexterity. In tests using a desktop computer and gaze sensors that tracked what part of the Dasher screen he was looking at, he reached a “typing” speed of up to 20 words a minute.
John Willis, director of the Varrier-Jones Trust, a charity addressing disabled issues, is impressed with Dasher. Born without hands or feet, he’s accustomed to aids like voice-recognition systems. “The more Dasher learns about the type of writing you do, the faster it is to use,” he says. “I’ve written quite a lot of stuff on it now—it’s brilliant for first drafts.”
