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Guy Harris (talk | contribs) Teleprinters, not just Teletypes - the Friden Flexowriter was also used as a terminal, all the way back to Whirlwind I. |
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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
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
The function of a terminal is typically confined to transcription 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]]"<ref name=DicDumb>{{cite web |website=BusinessDictionary.com |title=What is dumb terminal? definition and meaning |url=http://www.businessdictionary.com/definition/dumb-terminal.html |access-date=March 13, 2019 |archive-date=August 13, 2020 |archive-url=https://web.archive.org/web/20200813062015/http://www.businessdictionary.com/definition/dumb-terminal.html |url-status=dead }}</ref> or a [[thin client]].<ref>Thin clients came later than dumb terminals</ref><ref>the term "thin client" was coined in 1993) {{cite web |url=https://www.ft.com/content/dc70f841-54b7-3ef1-abf0-d6f32b270f76 |archive-url=https://ghostarchive.org/archive/20221210/https://www.ft.com/content/dc70f841-54b7-3ef1-abf0-d6f32b270f76 |archive-date=December 10, 2022 |url-access=subscription |url-status=live |title=Is this, finally, the thin client from Oracle? |date=June 2, 2009 |first=Richard |last=Waters}}</ref> In the era of serial ([[RS-232]]) terminals there was a conflicting usage of the term "smart terminal" as a dumb terminal with no user-accessible local computing power but a particularly rich set of control codes for manipulating the display; this conflict was not resolved before hardware serial terminals became obsolete.
The use of terminals decreased over time as computing shifted from [[command line interface]] (CLI) to [[graphical user interface]] (GUI) and from [[time-sharing]] on large computers to personal computers and [[handheld device]]s. Today, users generally interact with a server over high-speed networks using a [[Web browser]] and other network-enabled GUI applications. Today, a [[terminal emulator]] application provides the capabilities of a physical terminal {{endash}} allowing interaction with the [[operating system]] [[Shell (computing)|shell]] and other CLI applications.
==History==
The console of [[Konrad Zuse]]'s [[Z3 (computer)|Z3]] had a keyboard in 1941, as did the [[Z4 (computer)|Z4]] in 1942–1945. However, these consoles could only be used to enter numeric inputs and were thus analogous to those of calculating machines; programs, commands, and other data were entered via paper tape. Both machines had [[blinkenlights|a row of display lamps]] for results.
In 1956, the [[Whirlwind I|Whirlwind Mark I]] computer became the first computer equipped with a keyboard-printer combination with which to support direct input<ref
==Categories==
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Early user terminals connected to computers were, like the Flexowriter, electromechanical [[teleprinter]]s/teletypewriters (TeleTYpewriter, TTY), such as the [[Teletype Model 33]], originally used for [[telegraphy]]; early Teletypes were typically configured as [[Teletype Corporation#KSR|Keyboard Send-Receive]] (KSR) or [[Teletype Corporation#ASR|Automatic Send-Receive]] (ASR). Some terminals, such as the ASR Teletype models, included a [[paper tape]] reader and punch which could record output such as a program listing.
Custom-designs keyboard/printer terminals that came later included the [[IBM 2741]] (1965)<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology3.html |title=DPD chronology |website=[[IBM]] |date=January 23, 2003 |quote=1965 ... IBM 2741 ... July 8.}}</ref> and the [[DECwriter]] (1970).<ref name=Phil.DECw36>{{cite web |url=https://biztechmagazine.com/article/2017/03/dec-la36-dot-matrix-printer-made-business-printing-faster-and-more-efficient |title=The DEC LA36 Dot Matrix Printer Made Business Printing Faster and more efficient |date=March 17, 2017 |quote=[[Digital Equipment Corporation]] .. debuted the DECwriter LA30 in 1970. |first=Phil |last=Goldstein}}</ref> Respective top speeds of teletypes, IBM 2741 and the LA30 (an early DECwriter) were 10, 15 and 30
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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)}}===
A '''video display unit''' (VDU) displays information on a screen rather than printing text to paper and typically uses a [[cathode-ray tube]] (CRT). VDUs in the 1950s were typically designed for displaying graphical data rather than text and were used in, e.g., experimental computers at institutions
[[File:IBM 2260.jpg|thumb|180px|[[IBM 2260]]]]
Two early landmarks in the development of the VDU were the [[Univac Uniscope]]<ref>{{cite web|url=https://archive.computerhistory.org/resources/text/Remington_Rand/UNIVAC.UNISCOPE_300.ca1960.102646317.pdf | title=Uniscope brochure|access-date=2021-05-23}}</ref><ref>{{cite manual
| title = Uniscope 100 - Display Terminal - General Description
| id = UP-7701
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*[[Burroughs Corporation]] TD-830
*[[AT&T]] Dataspeed 40 (3270 clone manufactured by [[Teletype Corporation]])
*[[TeleVideo]] 912
*[[Tandem Computers]] VT6530
*[[Hewlett-Packard]] [[HP 2640|VT2640]]<ref>{{cite news|title=HP 3000s, IBM CPUs Get On-Line Link|url=https://books.google.com/books?id=Z62ZAojaNzYC&q=%22block+mode+terminal%22&pg=PA35|access-date=November 27, 2012|newspaper=Computerworld|date=March 24, 1980}}</ref>
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|journal=[[IEEE Transactions on Computers]] |s2cid=27102280 |date=1971 |volume=C-20 |issue=8 |pages=878–881 |doi=10.1109/T-C.1971.223364 |quote=Terminal cost is currently about $10,000}}</ref>
Most terminals today{{when|date=June 2022}} are graphical; that is, they can show images on the screen. The modern term for graphical terminal is "[[thin client]]".{{Citation needed|date=June 2019}} A thin client typically uses a protocol
Modern graphic terminals allow display of images in color, and of text in varying sizes, colors, and [[font]]s (type faces).{{clarify|date=June 2022}}
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Some dumb terminals had been able to respond to a few escape sequences without needing microprocessors: they used multiple [[printed circuit board]]s with many [[integrated circuit]]s; the single factor that classed a terminal as "intelligent" was its ability to ''process'' user-input within the terminal—not interrupting the main computer at each keystroke—and send a block of data at a time (for example: when the user has finished a whole field or form). Most terminals in the early 1980s, such as ADM-3A, TVI912, Data General D2, DEC [[VT52]], despite the introduction of ANSI terminals in 1978, were essentially "dumb" terminals, although some of them (such as the later ADM and TVI models) did have a primitive block-send capability. Common early uses of local processing power included features that had little to do with off-loading data processing from the [[host (network)|host computer]] but added useful features such as printing to a local printer, buffered serial data transmission and serial handshaking (to accommodate higher serial transfer speeds), and more sophisticated character attributes for the display, as well as the ability to switch emulation modes to mimic competitor's models, that became increasingly important selling features during the 1980s especially, when buyers could mix and match different suppliers' equipment to a greater extent than before.
The advance in microprocessors and lower memory costs made it possible for the terminal to handle editing operations such as inserting characters within a field that may have previously required a full screen-full of characters to be re-sent from the computer, possibly over a slow modem line. Around the mid-1980s most intelligent terminals, costing less than most dumb terminals would have a few years earlier, could provide enough user-friendly local editing of data and send the completed form to the main computer. Providing even more processing possibilities, workstations
Another of the motivations for development of the [[microprocessor]] was to simplify and reduce the electronics required in a terminal. That also made it practicable to load several "personalities" into a single terminal, so a Qume QVT-102 could emulate many popular terminals of the day, and so be sold into organizations that did not wish to make any software changes. Frequently emulated terminal types included:
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===Contemporary===
{{Unreferenced section|date=May 2023}}
In and around the 1990s
In a GUI environment, such as the [[X Window System]], the display can show multiple programs {{endash}} each in its own window {{endash}} rather than a single stream of text associated with a single program. As a terminal emulator runs in a GUI environment to provide command-line access, it alleviates the need for a physical terminal and allows for multiple windows running separate emulators.
▲In the 1990s especially, "thin clients" and [[X terminal]]s have combined economical local processing power with central, shared computer facilities to retain some of the advantages of terminals over personal computers:
[[File:KNOPPIX_booting.png|thumb|300x300px|Knoppix system console showing the boot process]]
One meaning of '''system console''', '''computer console''', '''root console''', '''operator's console''', or simply '''console''' is the text entry and display device for system administration messages, particularly those from the [[BIOS]] or [[boot loader]], the [[Kernel (operating system)|kernel]], from the [[init]] system and from the [[Syslog|system logger]]. It is a physical device consisting of a keyboard and a printer or screen, and traditionally is a [[text terminal]], but may also be a [[graphical terminal]].
Another, older, meaning of system console, computer console, '''hardware console''', operator's console or simply console is a hardware component used by an [[Computer operator|operator]] to control the hardware, typically some combination of [[front panel]], keyboard/printer and keyboard/display.
=== History ===
[[File:IBM_1620_Model_1.jpg|thumb|[[IBM 1620]] console, with a typewriter and front panel]]
Prior to the development of alphanumeric [[Cathode-ray tube|CRT]] system consoles, some computers such as the [[IBM 1620]] had console typewriters and [[Front panel|front panels]] while the very first electronic [[stored-program computer]], the [[Manchester Baby]], used a combination of electromechanical switches and a CRT to provide console functions—the CRT displaying memory contents in binary by mirroring the machine's [[Williams tube|Williams-Kilburn tube]] CRT-based RAM.
Some early operating systems supported either a single keyboard/print or keyboard/display device for controlling the OS. Some also supported a single alternate console, and some supported a [[Hard copy|hardcopy]] console for retaining a record of commands, responses and other console messages. However, in the late 1960s it became common for operating systems to support many more consoles than 3, and operating systems began appearing in which the console was simply any terminal with a privileged user logged on.
On early [[Minicomputer|minicomputers]], the console was a '''serial console''', an [[RS-232]] serial link to a terminal such as a [[Teletype Model 33|ASR-33]] or, later, a terminal from [[Digital Equipment Corporation]] (DEC), e.g., [[DECwriter|DECWriter]], [[VT100]]. This terminal was usually kept in a secured room since it could be used for certain privileged functions such as halting the system or selecting which media to boot from. Large [[Midrange computer|midrange systems]], e.g. those from [[Sun Microsystems]], [[Hewlett-Packard]] and [[IBM]],{{cn|reason=I know of no current IBM midrange system that still uses a serial console.|date=January 2022}} still use serial consoles. In larger installations, the console ports are attached to multiplexers or network-connected multiport serial servers that let an operator connect a terminal to any of the attached servers. Today, serial consoles are often used for accessing [[Headless computer|headless systems]], usually with a [[terminal emulator]] running on a [[laptop]]. Also, routers, enterprise [[Network switch|network switches]] and other telecommunication equipment have RS-232 serial console ports.
On [[Personal computer|PCs]] and [[Workstation|workstations]], the computer's attached [[Computer keyboard|keyboard]] and [[Computer monitor|monitor]] have the equivalent function. Since the monitor cable carries video signals, it cannot be extended very far. Often, installations with many servers therefore use keyboard/video multiplexers ([[KVM switch|KVM switches]]) and possibly video amplifiers to centralize console access. In recent years, [[KVM/IP]] devices have become available that allow a remote computer to view the video output and send keyboard input via any TCP/IP network and therefore the [[Internet]].
▲{{See also|System console}}
Some PC [[BIOS|BIOSes]], especially in servers, also support serial consoles, giving access to the BIOS through a serial port so that the simpler and cheaper serial console infrastructure can be used. Even where BIOS support is lacking, some [[Operating system|operating systems]], e.g. [[FreeBSD]] and [[Linux]], can be configured for serial console operation either during bootup, or after startup.
Starting with the [[IBM 9672]], IBM large systems have used a [[IBM Hardware Management Console|Hardware Management Console]] (HMC), consisting of a PC and a specialized application, instead of a 3270 or serial link. Other IBM product lines also use an HMC, e.g., [[IBM System p|System p]].
It is usually possible to [[Logging (computer security)|log in]] from the console. Depending on configuration, the operating system may treat a login session from the console as being more trustworthy than a login session from other sources.
==Emulation==
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{{Commons category|Data terminals}}
* [http://terminals-wiki.org/ The Terminals Wiki], an encyclopedia of computer terminals.
* [http://tldp.org/HOWTO/Text-Terminal-HOWTO.html Text Terminal HOWTO] from tldp.org
* [http://www.linusakesson.net/programming/tty/index.php The TTY demystified] from linussakesson.net
* {{webarchive |url=https://web.archive.org/web/20100523190056/http://www.cs.utk.edu/~shuford/terminal |date=May 23, 2010 |title=Video Terminal Information }}
* [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31999L0005:EN:NOT Directive 1999/5/EC of the European Parliament and of the Council of 9 March 1999 on radio equipment and telecommunications terminal equipment and the mutual recognition of their conformity (R&TTE Directive)]
* [http://www.epocalc.net/php/liste_models.php?texte=&look=All+fields&yearmax=2018&nocomp=pc&cat=Terminal
* [https://invisible-island.net/vttest/ VTTEST – VT100/VT220/XTerm test utility] {{dash}} A terminal test utility by Thomas E. Dickey
[[Category:Computer terminals| ]]
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