Computer terminal: Difference between revisions

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[[File:IBM_2741_(I197205).png|thumb|right|[[IBM 2741]], a widely emulated computer terminal in the 1960s and 1970s<br>(keyboard/printer)]]

A '''computer terminal''' is an electronic or [[electromechanical]] [[computer hardware|hardware]] device that can be used for entering data into, and transcribing<ref>E.g., displaying, printing, punching.</ref> data from, a [[computer]] or a [[computing]] system.<ref>similar to a paraphrase of an [[Oxford English Dictionary]] definition. {{cite web |url=https://english.stackexchange.com/questions/131511/what-is-the-etymology-of-computer-terminal |title=What is the etymology of "[computer] terminal"?}} Based on OED, B.2.d. (terminal), the paraphrase says that a terminal is a device for feeding data into a computer or receiving its output, especially one that can be used by a person for two-way communication with a computer.</ref> Most early computers only had a [[front panel]] to input or display bits and had to be connected to a terminal to print or input text through a keyboard. [[Teleprinter]]s were used as early-day hard-copy terminals<ref name=":0">{{cite web |url=http://www.samhallas.co.uk/repository/telegraph/teletype_story.pdf |title=The Teletype Story}}</ref><ref name="flexowriter-whirlwind">{{cite web|url=https://www.computerhistory.org/timeline/1956/|title=Direct keyboard input to computers|access-date=2024-01-11|archive-date=2017-07-17|archive-url=https://web.archive.org/web/20170717231119/http://www.computerhistory.org/timeline/1956/#169ebbe2ad45559efbc6eb35720ba5f3|url-status=live}}</ref> and predated the use of a computer<ref name=":0" /> screen by decades. The computer would typically transmit a line of data which would be printed on paper, and accept a line of data from a keyboard over a [[Serial communication|serial]] or other interface. Starting in the mid-1970s with [[microcomputers]] such as the [[Sphere 1]], [[Sol-20]], and [[Apple I]], display circuitry and keyboards began to be integrated into [[personal computer|personal]] and [[workstation]] computer systems, with the computer handling character generation and outputting to a [[Cathode-ray_tube|CRT display]] such as a [[computer monitor]] or, sometimes, a consumer TV, but most larger computers continued to require terminals.

Early terminals were inexpensive devices but very slow compared to [[punched card]]s or [[punched tape|paper tape]] for input; with the advent of [[time-sharing]] systems, terminals slowly pushed these older forms of interaction from the industry. Related developments were the improvement of terminal technology and the introduction of inexpensive [[video display]]s. Early Teletypes only printed out with a communications speed of only 75 baud or 10 5-bit characters per second, and by the 1970s speeds of video terminals had improved to 2400 or 9600 {{units|2400|u=bps}}. Similarly, the speed of remote batch terminals had improved to {{units|4800|u=bps}} at the beginning of the decade and {{units|19.6|u=kbps}} by the end of the decade, with higher speeds possible on more expensive terminals.

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The DECwriter was the last major printing-terminal product. It faded away after 1980 under pressure from video display units (VDUs), with the last revision (the DECwriter IV of 1982) abandoning the classic teletypewriter form for one more resembling a desktop printer.

Printing terminals required that the print mechanism be away from the paper after a pause in the print flow, to allow an interactively typing user to see what they had just typed and make corrections, or to read a prompt string. As a dot-matrix printer, the DECwriter family would move the print head sideways after each pause, returning to the last print position when the next character came from the remote computer (or local echo).

===Video display unit{{anchor|Video display unit|VDU|VDUs|Video display units (VDUs)}}===