Most applications are written to work with the mouse as the primary pointing and selecting device. For pen and speech input on Tablet PC, the limitations of the mouse are apparent. The design and ergonomics of Tablet PC also restrict the success of handwriting input. More intrinsically, to take full advantage of the power of Tablet PC, your applications need greater real-time responsiveness than is possible with traditional Microsoft® Windows® mouse messages.
Because of these limitations, one of the key Tablet PC innovations is how easily users can employ the pen to enter input and issue commands. Pen activities include writing, pointing, selecting, and dragging. The core of effective pen interaction, however, is to make the use of digital ink and the use of traditional ink on paper as much alike as possible. This occurs if the pen is responsive and natural, which requires that events and messages related to pen movements and actions be sent directly to applications in real time. The existing architecture for Windows mouse messages does not permit this level of responsiveness in the event mechanism. This requires a mechanism that evaluates pen events in real time.
In addition to writing, users must be able to employ the pen to point and select, just as they do with a mouse. The pen must work with both existing applications that were developed for mouse usage only and newer applications that take advantage of the versatility of the pen.
For more information on making the pen more useful, see Making the Tablet Pen Work.