The IT infrastructure in organizations today is an outgrowth of over 50 years of evolution in computing platforms. We have identified five stages in this evolution, each representing a different configuration of computing power and infrastructure elements . The five eras are automated special-purpose machines, general-purpose mainframe and minicomputer computing, personal computers, client/server networks, and enterprise and Internet computing. These eras do not necessarily end for all organizations at the same time, and the technologies that characterize one era may also be used in another time period for other purposes. For example, some companies still run traditional mainframe or minicomputer systems. Mainframe computers today are used as massive servers supporting large Web sites and corporate enterprise applications.