Pen Computing

Pen Computing

 refers to a computer user-interface using a pen (or stylus) and tablet, rather than devices such as a keyboard, joysticks or a mouse.

Pen computing is also used to refer to the usage of mobile devices such as wireless tablet personal computers, PDAs and GPS receivers. The term has been used to refer to the usage of any product allowing for mobile communication. An indication of such a device is a stylus, generally used to press upon a graphics tablet or touchscreen, as opposed to using a more traditional interface such as a keyboard, keypad, mouse or touchpad.

Historically, pen computing (defined as a computer system employing a user-interface using a pointing device plus handwriting recognition as the primary means for interactive user input) predates the use of a mouse and graphical display by at least two decades, starting with the Stylator and RAND Tablet^[2] systems of the 1950s and early 1960s.

General techniques of pen computing are:

1. Pointing/locator input: The tablet and stylus are used as pointing devices, such as to replace a mouse. While a mouse is a relative pointing device (one uses the mouse to "push the cursor around" on a screen), a tablet is an absolute pointing device (one places the stylus where the cursor is to appear).
   There are a number of human factors to be considered when actually substituting a stylus and tablet for a mouse. For example, it is much harder to target or tap the same exact position twice with a stylus, so "double-tap" operations with a stylus are harder to perform if the system is expecting "double-click" input from a mouse.
   A finger can be used as the stylus on a touch-sensitive tablet surface, such as with a touchscreen.
2. Handwriting recognition: The tablet and stylus can be used to replace a keyboard, or both a mouse and a keyboard, by using the tablet and stylus in two modes:
   • Pointing mode: The stylus is used as a pointing device as above.
   • On-line Handwriting recognition mode: The strokes made with the stylus are analyzed as a "electronic ink", by software which recognizes the shapes of the strokes or marks as handwritten characters. The characters are then input as text, as if from a keyboard.
   Different systems switch between the modes (pointing vs. handwriting recognition) by different means, e.g.
   • by writing in separate areas of the tablet for pointing mode and for handwriting-recognition mode.
   • by pressing a special button on the side of the stylus to change modes.
   • by context, such as treating any marks not recognized as text as pointing input.
   • by recognizing a special gesture mark.
   The term "on-line handwriting recognition" is used to distinguish recognition of handwriting using a real-time digitizing tablet for input, as contrasted to "off-line handwriting recognition", which is optical character recognition of static handwritten symbols from paper.
3. Direct manipulation: The stylus is used to touch, press, and drag on simulated objects directly. The Wang Freestyle system ^[3] is one example. Freestyle worked entirely by direct manipulation, with the addition of electronic "ink" for adding handwritten notes.
4. Gesture recognition: This is the technique of recognizing certain special shapes not as handwriting input, but as an indicator of a special command.
   For example, a "pig-tail" shape (used often as a proofreader's mark) would indicate a "delete" operation. Depending on the implementation, what is deleted might be the object or text where the mark was made, or the stylus can be used as a pointing device to select what it is that should be deleted. With Apple's Newton OS, text could be deleted by scratching in a zig-zag pattern over the text which the user desired to remove.
   Recent systems have used digitizers which can recognize more than one "stylus" (usually a finger) at a time, and make use of Multi-touch gestures.
   The PenPoint OS was a special operating system which incorporated gesture recognition and handwriting input at all levels of the operating system. Prior systems which employed gesture recognition only did so within special applications, such as CAD/CAM applications or text processing.