ults to external destinations. Digital computer : It is a fast electronic calculating machine that accepts digitized input information, processes it according to a list of internally stored instructions, and produces the resulting output information. (1) Personal computer : It is the most common form of desktop computers. Desk top computers have processing and storage units, visual display and audio output units, and a keyboard that can all be located easily on a home or office desk. The storage media include hard disks, CD-ROMs and diskettes. Portable notebook computers are a compact version of the personal computers with all of these components packaged into single unit the size of a thin briefcase.