This is a demonstration of PenPoint, the pen-based operating system announced by GO Corp. this week, focusing on issues of user interface design. The user interface of PenPoint is built around the metaphor of a notebook, and combines the kinds of visual controls familiar from graphical user interfaces with the use of gestures to issue commands with the pen. Just as the graphical display and the mouse opened up a rich design space when they were pioneered at Xerox PARC in the 70's, the hand-held tablet and pen promise to open up a new design space today.