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 120 or the Magic Cap-line and was available 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 "PalmPr" (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.
Jeff Hawkins called this system "PowerPalmPrint" or P3. Other engineers at Palm revised and expanded the alphabet that Hawkins had created. Joe Sipher and Ron Marianetti created more characters and punctuation and also designed a prototype of Graffiti that ran on a PC with a tablet peripheral.
Graffiti was also implemented on the Apple Newton. In 2008 an unauthorized version of Graffiti was introduced for iOS (iPhone and iPad) devices. An Android version was released in 2010 by ACCESS CO., LTD. of Japan, which acquired the rights to Graffiti when it acquired PalmSource, Inc. in 2005.
The original Graffiti system was the subject of a lawsuit from Xerox, claiming it violated Xerox's patent relating to its Unistrokes technology (U.S. Patent 5,596,656, granted in 1997). The Unistrokes technology was invented at the Palo Alto Research Center (PARC) by David Goldberg. Palm got a demonstration of Unistrokes from PARC before they created their Graffiti system. During the original case, a court ruled that Palm violated Xerox's patent and ordered them to discontinue use of the original Graffiti system in further versions of its Palm OS software, which Palm did. It replaced the original Graffiti system with a licensed variant of the Jot system from Communication Intelligence Corporation, which Palm refers to as Graffiti 2. It differs from the original Graffiti system in various ways, though it does recognize some of the original keystrokes (except the input method for punctuation and "i", "k", "q", "t" and "4").
Palm later appealed the original court ruling both on the claim it violated Xerox's patent and as to the validity of the patent in the first place. An appeals court ruled in favor of Xerox with regard to the original ruling that Palm had violated its patent but sent the case back down to the lower court to decide whether the patent was valid to begin with. In 2004, a judge ruled in favor of Palm, saying Xerox's patent was not valid on the basis that "prior art references anticipate and render obvious the claim."  Xerox appealed the ruling and won, obtaining $US 22.5 million in retrospective licensing fees. Palm and Xerox agreed to not sue each other for seven years over certain patents, without publicly specifying which patents.
- Moon type — a writing system for the blind, using embossed symbols mostly derived from the Roman alphabet (but simplified)
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