Computer terminal

A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying or printing data from, a computer or a computing system. The teletype was an example of an early day hardcopy terminal, and predated the use of a computer screen by decades. The acronym CRT (cathode-ray tube), which once referred to a computer terminal, has come to refer to a type of screen of a personal computer. Early terminals were inexpensive devices but very slow compared to punched cards or paper tape for input, but as the technology improved and video displays were introduced, terminals pushed these older forms of interaction from the industry. A related development was timesharing systems, which evolved in parallel and made up for any inefficiencies of the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal. The function of a terminal is confined to display and input of data; a device with significant local programmable data processing capability may be called a 'smart terminal' or fat client. A terminal that depends on the host computer for its processing power is called a 'dumb terminal' or a thin client. A personal computer can run terminal emulator software that replicates the function of a terminal, sometimes allowing concurrent use of local programs and access to a distant terminal host system. The terminal of the first working programmable, fully automatic digital Turing-complete computer, the Z3, had a keyboard and a row of lamps to show results. Early user terminals connected to computers were electromechanical teleprinters/teletypewriters (TeleTYpewriter, TTY), such as the Teletype Model 33 ASR, originally used for telegraphy or the Friden Flexowriter. Keyboard/printer terminals that came later included the IBM 2741 (1965) and the DECwriter LA30 (1970). Respective top speeds of teletypes, IBM 2741 and LA30 were 10, 15 and 30characters per second. Although at that time 'paper was king' the speed of interaction was relatively limited. Early video computer displays were sometimes nicknamed 'Glass TTYs' ('glass Teletypes') or 'Visual Display Units' (VDUs), and used no CPU, instead relying on individual logic gates or very primitive LSI chips. Nevertheless, they quickly became extremely popular Input-Output devices on many different types of computer system once several suppliers gravitated to a set of common standards: The Datapoint 3300 from Computer Terminal Corporation was announced in 1967 and shipped in 1969, making it one of the earliest stand-alone display-based terminals. It solved the memory space issue mentioned above by using a digital shift-register design, and using only 72 columns rather than the later more common choice of 80.