Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The PenPoint OS was a product of GO Corporation and was one of the earliest operating systems written specifically for graphical tablets and personal digital assistants. It ran on AT&T's EO Personal Communicator as well as a number of Intel x86 powered tablet PCs including IBM's ThinkPad 700T series, NCR's 3125, 3130 and some of GRiD Systems' pen-based portables. Developers of the PenPoint OS included Robert Carr, who was involved with the Alto computer at Xerox PARC.