Information technology (IT) is a branch of engineering dealing with the use of computers and telecommunications equipment to store, retrieve, transmit and manipulate data.
The Information Technology Association of America has defined IT as “the study, design, development, application, implementation, support or management of computer-based information systems”.The term is commonly used as a synonym for computers and computer networks, but it also encompasses other information distribution technologies such as television and telephones.
Humans have been storing, retrieving, manipulating and communicating information since the Sumerians in Mesopotamia developed writing in about 3000 BC, but the term “information technology” in its modern sense first appeared in a 1958 article published in the Harvard Business Review; authors Leavitt and Whisler commented that “the new technology does not yet have a single established name. We shall call it information technology (IT).”Based on the storage and processing technology employed, it is possible to distinguish four distinct phases of IT development: pre-mechanical (3000 BC – 1450 AD), mechanical (1450-1840), electromechanical (1840-1940) and electronic.This article focuses on the latter of those periods, which began in about 1940.
Devices have been used to aid computation for thousands of years, probably initially in the form of a tally stick.The Antikythera mechanism, dating from about the beginning of the first century BC, is generally considered to be the earliest known mechanical analog computer; it is also the earliest known geared mechanism. Comparable geared devices did not emerge in Europe until the 16th century,[8] and it was not until 1645 that the first mechanical calculator capable of performing the four basic arithmetical operations was developed.
Electronic computers, using either relays or valves, began to appear in the early 1940s. The electromechanical Zuse Z3, completed in 1941, was the world’s first programmable computer, and by modern standards one of the first machines that could be considered a complete computing machine. Colossus, developed during the Second World War to decrypt German messages was the first electronic digital computer, but although programmable it was not general-purpose, being designed for a single task. Neither did it store its programs in memory; programming was carried out using plugs and switches to alter the internal wiring.[citation needed] The first recognisably modern electronic digital stored-program computer was the Manchester Small-Scale Experimental Machine (SSEM), which ran its first program on 21 June 1948.
Early electronic computers such as Colossus made use of punched tape, a long strip of paper on which data was represented by a series of holes, a technology now obsolete.Electronic data storage as used in modern computers dates from the Second World War, when a form of delay line memory was developed to remove the clutter from radar signals, the first practical application of which was the mercury delay line. The first random-access digital storage device was the Williams tube, based on a standard cathode ray tube, but the information stored in it and delay line memory was volatile in that it had to be continuously refreshed, and thus was lost once power was removed. The earliest form of non-volatile computer storage was the magnetic drum, invented in 1932 and used in the Ferranti Mark 1, the world’s first commercially available general-purpose electronic computer.
Most digital data today is still stored magnetically on devices such as hard disk drives, or optically on media such as CD-ROMs. It has been estimated that the worldwide capacity to store information on electronic devices grew from less than 3 exabytes in 1986 to 295 exabytes in 2007,doubling roughly every 3 years.