Information technology is not a subset of information and communication technology.
Based on the storage and processing technologies employed, it is possible to distinguish four distinct phases of IT development: pre-mechanical (3000 BC  1450 AD), mechanical (14501840), electromechanical (18401940), and electronic (1940 to present)
 The responsibilities of those working in the field include network administration, software development and installation, and the planning and management of an organization's technology life cycle, by which hardware and software are maintained, upgraded, and replaced

