Handheld Computer

A handheld  computer,sometimes referred to as an Ultra-Mobile PC (UMPC), is a computer small enough to fit in one hand (Figure 1-19). Because of their reduced size, the screens on handheld comput¬ers are small. Many handheld computers com¬municate wirelessly with other devices or computers and also include a digital pen or stylus for input. Similar to a digital pen, a stylus is a small metal or plastic device that looks like a ballpoint pen but uses pres¬sure instead of ink to write, draw, or make selections.
Some handheld computers have minia-ture or specialized key-boards. Many handheld computers are industry-specific and serve the needs of mobile employ¬ees, such as meter readers and parcel delivery people, whose jobs require them to move from place to place.
PDA   A PDA (personal digital assistant) provides personal organizer functions such as a calendar, an appointment book, an address book, a calculator, and a notepad (Figure 1-20). Most PDAs also offer a variety of other appli¬cation software such as word processing, spreadsheet, personal finance, and games. The primary input device of a PDA is a stylus. Some PDAs have a built-in miniature keyboard. If you prefer to type on a PDA that does not have a keyboard, you can insert the PDA in a special separate keyboard. Some PDAs also support voice input, have built-in cameras, and can function as a portable media player.