A handheld computer is a computer that can conveniently be stored in a pocket (of sufficient size) and used while you're holding it. Today's handheld computers, which are also called personal digital assistants (PDAs), can be divided into those that accept handwriting as input and those with small keyboards. The original handheld that accepted handwriting was Apple's Newton, which was later withdrawn from the market. Today, the most popular handheld that accepts handwritten input is the PalmPilot from 3Com. Philips, Casio, NEC, Compaq, and other companies make handhelds with small keyboards.
Handheld computers are typically used for personal information manager (PIM) types of applications: maintaining schedules, keeping names and phone numbers, doing simple calculations, taking notes, and, with a modem, exchanging e-mail and getting information from the Web. Keyboards have tiny keys that take getting used to. Those that handle handwriting also impose constraints and require some learning. Nevertheless, this class of computer is widely sold and appreciated by many users.
Hewlett-Packard has recently introduced the first handheld computer with a color display. A number of companies now combine voice and data telephone service using cellular telephone or other wireless technologies with the handheld computer in a single device.