rotation in any direction is used for the first time or when the Newton device is reset. Handwriting recognition In initial versions (Newton OS 1.x) the handwriting recognition gave extremely mixed results for users and was sometimes inaccurate. The original handwriting recognition engine was called Calligrapher, and was licensed from a Russian company called Paragraph International. Calligrapher's design was quite sophisticated; it attempted to learn the user's natural handwriting, using a database of known words to make guesses as to what the user was writing, and could interpret writing anywhere on the screen, whether hand-printed, in cursive, or a mix of the two. By contrast, Palm Pilot's Graffiti had a less sophisticated design than Calligrapher, but was sometimes found to be more accurate and precise due to its reliance on a fixed, predefined stroke alphabet. The stroke alphabet used letter shapes which resembled standard handwriting, but which were modified to be both simple and very easy to differentiate. Palm Computing also released two versions of Graffiti for Newton devices. The Newton version sometimes performed better and could also show strokes as they were being written as input was done on the display itself, rather than on a silkscreen area. For editing text, Newton had a very intuitive system for handwritten editing, such as scratching out words to be deleted, circling text to be selected, or using written carets to mark inserts. Later releases of the Newton operating system retained the original recognizer for compatibility, but added a hand-printed-text-only (not cursive) recognizer, called "Rosetta", which was developed by Apple, included in version 2.0 of the Newton operating system, and refined in Newton 2.1. Rosetta is generally considered a significant improvement and many reviewers, testers, and most users consider the Newton 2.1 handwriting recognition software better than any of the alternatives even 10 years after it was introduced. Recognition and computation of handwritten horizontal and vertical formulas such as "1 + 2 =" was also under development but never released. However, users wrote similar programs which could evaluate mathematical formulas using the Newton OS Intelligent Assistant, a unique part of every Newton device. The handwriting recognition and parts of the user interface for the Newton are best understood in the context of the broad history of pen computing, which is quite extensive. A vital feature of the Newton handwriting recognition system is the modeless error correction. That is, correction done in situ