Graffiti (Palm OS)

Graffiti is an essentially single-stroke shorthand handwriting recognition system used in PDAs based on the Palm OS. Graffiti was originally written by Palm, Inc. as the recognition system for GEOS-based devices such as HP's OmniGo 100 and 120 or the Magic Cap-line and was available as an alternate recognition system for the Apple Newton MessagePad, when NewtonOS 1.0 couldn't recognize handwriting very well. Graffiti also runs on the Windows Mobile platform, where it is called "Block Recognizer", and on the Symbian UIQ platform as the default recognizer and was available for Casio's Zoomer PDA.

The software is based primarily on a neography of upper-case characters that can be drawn blindly with a stylus on a touch-sensitive panel. Since the user typically cannot see the character as it is being drawn, complexities have been removed from four of the most difficult letters. "A'" "F", "K" and "T" all are drawn without any need to match up a cross-stroke.

Graffiti was developed by Jeff Hawkins, who had previously created "PalmPrint" (the character recognition system used by the Casio Zoomer) to recognize natural handwriting. By using a simpler alphabet, computers could easily recognize handwriting. Hawkins believed that people would take the time to learn Graffiti just as people learn to touch-type. Hawkins recalled his insight: "And then it came to me in a flash. Touch-typing is a skill you learn."

Jeff Hawkins also envisioned a single area for writing letters on top of each other. Other pen computers used traditional writing from left to right. The drawback of this is that users run out of screen space after a few words. Graffiti used a different approach. Instead of writing letters normally, users would write one letter on top of another, lifting the pen between them. This meant that each letter had to be one continuous stroke—so, for example, it would be impossible to dot an "i"—but it made it easy for the computer to simply recognize letters in the order they were written, with added glyphs for things like spaces and upper case.

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