The 1980’s brought a major change in the way data were processed in organizations. Traditional centralized data processing on microcomputers gave way to decentralized or distributed personalized applications running on desktop and notebooks sized computers. Around the world, millions of computers are being linked together in networks of all sizes. This development continues today as Internet ties local systems into a global network. A network is a system of computers interconnected in order to share information and resources. Networks are vital to businesses