The Livescribe Pulse Smartpen turns a sheet of paper into a computer interface. Write down an equation, and the solution appears on the pen's screen. The pen also has a built-in audio recorder: record a lecture, and by tapping the pen on a line from a page of handwritten notes, you can call up the corresponding section of the recording. The pen's computational features work so long as the user writes on paper printed with a special pattern, which is read by cameras in the pen's tip.

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