Handheld computers
A hand-held computer offers the main functionality of a laptop in a smaller package. Although extremely convenient to carry, handheld computers have not replaced notebook computers because of their small keyboards and screens. The most popular hand-held computers are those that are specifically designed to provide personal information functions, such as a calendar and address book.
They feature a full QWERTY style keyboard and a landscape display, and operate similarly to a desktop PC, often with the Windows CE OS. Due to the keyboard these are probably best suited to use where there is a stable platform available. Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. However, these pen-based devices rely on handwriting recognition technologies.