There are five stages of IT infrastructure evolution. IT infrastructure in the earliest edge consisted of specialized electronic accounting machines that were primitive computers used for accounting tasks. IT infrastructure in the mainframe era consist of a mainframe performing centralized processing that could be networked to thousands of terminal and eventually some decentralized and departmental computing using networked minicomputers. The personal computer era in IT infrastructure has been dominated the widespread use of standalone desktop computers with office productivity tools. The predominant infrastructure in the client server era consists of desktop or laptop clients network to more powerful server computers that handle most of the data management and processing. The enterprise internet computing era is defined large numbers of PCS linked into local area networks and growing use of standards and software to link disparate networks and devices into an enterprise wide networks so that information can flow freely across the organization.