![IBM_2741_(I197205)](https://upload.wikimedia.org/wikipedia/commons/2/23/IBM_2741_%28I197205%29.png)
A computer terminal is an electronic or
electromechanical
In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...
hardware device that can be used for entering data into, and transcribing data from, a
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
or a
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...
system. The
teletype
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades.
Early terminals were inexpensive devices but very slow compared to
punched card
A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to di ...
s or
paper tape
Five- and eight-hole punched paper tape
Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop
Punched tape or perforated paper tape is a form of data storage ...
for input, yet as the technology improved and
video display
A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...
s were introduced, terminals pushed these older forms of interaction from the industry. A related development was
time-sharing
In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1
Its emergence a ...
systems, which evolved in parallel and made up for any inefficiencies in the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal or terminals.
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
In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.
The term often refers specifically to triglycerides (triple est ...
. A terminal that depends on the host computer for its processing power is called a "
dumb terminal"
or a
thin client
In computer networking, a thin client is a simple (low-performance) computer that has been optimized for establishing a remote connection with a server-based computing environment. They are sometimes known as ''network computers'', or in th ...
. A personal computer can run
terminal emulator
A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote termin ...
software that replicates functions of a real-world terminal, sometimes allowing concurrent use of local programs and access to a distant ''terminal host'' system, either over a direct serial connection or over a network using, e.g.,
SSH
The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution.
SSH applications are based on a ...
.
History
The console of
Konrad Zuse
Konrad Ernst Otto Zuse (; 22 June 1910 – 18 December 1995) was a German civil engineer, pioneering computer scientist, inventor and businessman. His greatest achievement was the world's first programmable computer; the functional program-c ...
's
Z3 had a keyboard in 1941, as did the
Z4 in 1942–1945. But 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 a row of display lamps for results.
In 1955, the
Whirlwind Mark I computer was the first computer equipped with a keyboard-printer combination with which to support direct input of data and commands and output of results. The device was a
Friden Flexowriter, which would continue to serve this purpose on many other early computers well into the 1960s.
Hard-copy terminals
Early user terminals connected to computers were, like the Flexowriter, electromechanical
teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
s/teletypewriters (TeleTYpewriter, TTY), such as the
Teletype Model 33
The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. It is less rugged and cost less than earlier Teletype machines. The Teletype Corporation introduced the Model 33 as a commercial product in 1963 after ...
, originally used for
telegraphy
Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...
; early Teletypes were typically configured as Keyboard Send-Receive (KSR) or Automatic Send-Receive (ASR), the latter including a
paper tape
Five- and eight-hole punched paper tape
Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop
Punched tape or perforated paper tape is a form of data storage ...
reader and punch. This led to the use of the
current loop interface that was already used in telegraphy, as well as a thriving market in surplus machines for computer use.
Custom-designs keyboard/printer terminals that came later included the
IBM 2741 (1965) and the
DECwriter (1970).
Respective top speeds of teletypes, IBM 2741 and the LA30 (an early DECwriter) were 10, 15 and 30
characters per second. Although at that time "paper was king"
[ the speed of interaction was relatively limited.
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.
]
VDUs
A ''video display unit'' (VDU) displays information on a screen rather than printing text to paper and typically uses a cathode-ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictur ...
(CRT). Due to that technology these devices were often called "CRTs". VDUs in the 1950s were typically designed for displaying graphical data rather than just text. CRT displays in that time frame were used in, e.g., experimental computers at MIT; Commercial computer from, e.g., DEC, ERA
An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy, a calendar era used for a given calendar, or the geological eras defined for the history of Earth.
Compa ...
, IBM, UNIVAC
UNIVAC (Universal Automatic Computer) was a line of electronic digital stored-program computers starting with the products of the Eckert–Mauchly Computer Corporation. Later the name was applied to a division of the Remington Rand company an ...
; military computers for, e.g., BMEWS
The RCA 474L Ballistic Missile Early Warning System (BMEWS, "474L System", Project 474L) was a United States Air Force Cold War early warning radar, computer, and communications system, for ballistic missile detection. The network of twelve ra ...
, BUIC, SAGE
Sage or SAGE may refer to:
Plants
* ''Salvia officinalis'', common sage, a small evergreen subshrub used as a culinary herb
** Lamiaceae, a family of flowering plants commonly known as the mint or deadnettle or sage family
** ''Salvia'', a large ...
.
Two early landmarks in the development of the VDU were the Univac Uniscope 300 and the IBM 2260, both in 1964. Both were block-mode terminals designed to ship a page at a time, rather than character-mode devices. The Hazeltine 2000
The Hazeltine 2000 is one of the first general-purpose "smart" computer terminals, introduced in October 1970 at a price of $2,995 (). While earlier terminal systems included "smart" editing features, notably the IBM 2260, the Hazeltine 2000 was ...
of 1970 was a notable later product of the same kind.
The Datapoint 3300
The DataPoint 3300 was the first computer terminal manufactured by Computer Terminal Corporation, later renamed Datapoint, announced in 1967 and shipping in 1969. Since this terminal was intended to replace a teleprinter such as those made by Telet ...
from Computer Terminal Corporation
Datapoint Corporation, originally known as Computer Terminal Corporation (CTC), was a computer company based in San Antonio, Texas, United States. Founded in July 1968 by Phil Ray and Gus Roche, its first products were, as the company's initial ...
, announced in 1967 and shipped in 1969, was a character-mode device that emulated a Model 33 Teletype. This reflects the fact that early character-mode terminals were often deployed to replace teletype machines as a way to reduce operating costs.
The next generation of VDUs went beyond teletype emulation with an addressable cursor that gave them the ability to paint two-dimensional displays on the screen. Despite this, early devices of this type were often called "Glass TTYs". The classic era of the VDU began in the early 1970s and was closely intertwined with the rise of time sharing computers. Important early products were the ADM-3A, VT52
The VT50 was a CRT-based computer terminal introduced by Digital Equipment Corporation (DEC) in July 1974. It provided a display with 12 rows and 80 columns of upper-case text, and used an expanded set of control characters and forward-only scro ...
, and VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special f ...
. These devices used no CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...
, instead relying on individual logic gate
A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic gate, ...
s or very primitive LSI chips. This made them inexpensive and they quickly became extremely popular Input-Output devices on many different types of computer system, often replacing earlier and more expensive printing terminals.
After 1970 several suppliers gravitated to a set of common standards:
* ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...
character set (rather than, say, EBCDIC or anything specific to one company), but early/economy models often supported only capital letters (such as the original ADM-3
The ADM-3A was an influential early video display terminal, introduced in 1976. It was manufactured by Lear Siegler and had a 12-inch screen displaying 12 or 24 lines of 80 characters. It set a new industry low single unit price of $995. Its "du ...
, the Data General model 6052 – which could be upgraded to a 6053 with a lower-case character ROM – and the Heathkit H9)
* RS-232
In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such a ...
serial ports (25-pin, ready to connect to a modem, yet some manufacturer-specific pin usage extended the standard, e.g. for use with 20-mA current loops)
* 24 lines (or possibly 25 – sometimes a special status line) of 72 or 80 characters of text (80 was the same as IBM punched cards). Later models sometimes had two character-width settings.
* Some type of cursor that can be positioned (with arrow keys or "home" and other direct cursor address setting codes).
* Implementation of at least 3 control codes: Carriage Return (Ctrl-M), Line-Feed (Ctrl-J), and Bell (Ctrl-G), but usually many more, such as escape sequences to provide underlining, dim or reverse-video character highlighting, and especially to clear the display and position the cursor.
The experimental era of serial VDUs culminated with the VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special f ...
in 1978. By the early 1980s, there were dozens of manufacturers of terminals, including Lear-Siegler
Lear Siegler Incorporated (LSI) is a diverse American corporation established in 1962. Its products range from car seats and brakes to weapons control systems for military fighter planes. The company's more than $2 billion-a-year annual sales come ...
, ADDS Applied Digital Data Systems (ADDS) was a supplier of video display computer terminals, founded in 1969 by Leeam Lowin and William J. Catacosinos. Lowin simultaneously founded Solid State Data Sciences (SSDS). SSDS was one of the first developers ...
, Data General, DEC, Hazeltine Corporation
Hazeltine Corporation was a defense electronics company which is now part of BAE Systems Inc.
History 1924–1986
The company was founded in 1924 by investors to exploit the Neutrodyne patent of Dr. Louis Alan Hazeltine. Headquartered in Gree ...
, Heath/Zenith, Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
, IBM, TeleVideo
TeleVideo Corporation was a U.S. company that achieved its peak of success in the early 1980s producing computer terminals. TeleVideo was founded in 1975 by K. Philip Hwang, a Utah State University, Hanyang University graduate born in South Kore ...
, Volker-Craig, and Wyse
WYSE (970 AM) is a radio station located in Canton, North Carolina, that simulcasts WISE's sports format from Asheville, North Carolina. Owned by the Asheville Radio Group subsidiary of Saga Communications, the station is licensed by the Fede ...
, many of which had incompatible command sequences (although many used the early ADM-3 as a starting point).
The great variations in the control codes between makers gave rise to software that identified and grouped terminal types so the system software would correctly display input forms using the appropriate control codes; In Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
systems the termcap
Termcap (''terminal capability'') is a software library and database used on Unix-like computers. It enables programs to use display computer terminals in a device-independent manner, which greatly simplifies the process of writing portable text m ...
or terminfo
Terminfo is a library and database that enables programs to use display terminals in a device-independent manner. Mary Ann Horton implemented the first terminfo library in 1981–1982 as an improvement over termcap. The improvements include
* fast ...
files, the stty utility, and the TERM environment variable would be used; in Data General's Business BASIC software, for example, at login-time a sequence of codes were sent to the terminal to try to read the cursor's position or the 25th line's contents using a sequence of different manufacturer's control code sequences, and the terminal-generated response would determine a single-digit number (such as 6 for Data General Dasher terminals, 4 for ADM 3A/5/11/12 terminals, 0 or 2 for TTYs with no special features) that would be available to programs to say which set of codes to use.
The great majority of terminals were monochrome, manufacturers variously offering green, white or amber and sometimes blue screen phosphors. (Amber was claimed to reduce eye strain). Terminals with modest color capability were also available but not widely used; for example, a color version of the popular Wyse WY50, the WY350, offered 64 shades on each character cell.
VDUs were eventually displaced from most applications by networked personal computers, at first slowly after 1985 and with increasing speed in the 1990s. However, they had a lasting influence on PCs. The keyboard layout of the VT220
The VT220 is a computer terminal introduced by Digital Equipment Corporation (DEC) in November 1983. The VT240 added monochrome ReGIS vector graphics support to the base model, while the VT241 did the same in color. The 200 series replaced the s ...
terminal strongly influenced the Model M
Model M designates a group of computer keyboards designed and manufactured by IBM starting in 1985, and later by Lexmark International, Maxi Switch, and Unicomp. The keyboard's many variations have their own distinct characteristics, with ...
shipped on IBM PCs from 1985, and through it all later computer keyboards.
Although flat-panel displays were available since the 1950s, cathode-ray tubes continued to dominate the market until the personal computer had made serious inroads into the display terminal market. By the time cathode-ray tubes on PCs were replaced by flatscreens after the year 2000, the hardware computer terminal was nearly obsolete.
"Intelligent" terminals
An "intelligent" terminal does its own processing, usually implying a microprocessor is built in, but not all terminals with microprocessors did any real processing of input: the main computer to which it was attached would have to respond quickly to each keystroke. The term "intelligent" in this context dates from 1969.
Notable examples include the IBM 2250
The IBM 2250 Graphics Display Unit was a vector graphics display system by IBM for the System/360; the Model IV attached to the IBM 1130.
Overview
The IBM 2250 Graphics Display Unit was announced with System/360 in 1964. A complete 2250 III sys ...
, predecessor to the IBM 3250 and IBM 5080, and IBM 2260, predecessor to the IBM 3270
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971
and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text ...
, introduced with System/360
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...
in 1964.
Most terminals were connected to minicomputer
A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...
s or mainframe computer
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...
s and often had a green or amber screen. Typically terminals communicate with the computer via a serial port
In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. ...
via a null modem
Null modem is a communication method to directly connect two DTEs (computer, terminal, printer, etc.) using an RS-232 serial cable. The name stems from the historical use of RS-232 cables to connect two teleprinter devices or two modems in order ...
cable, often using an EIA Eia or EIA may refer to:
Medicine
* Enzyme immunoassay
* Equine infectious anemia
* Exercise-induced anaphylaxis
* Exercise-induced asthma
* External iliac artery
Transport
* Edmonton International Airport, in Alberta, Canada
* Erbil Internation ...
RS-232
In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such a ...
or RS-422 or RS-423 or a current loop serial interface. IBM systems typically communicated over a Bus and Tag
Bus and Tag is an "IBM standard for a computer peripheral interface", and was commonly used to connect their mainframe computers to peripheral devices such as line printers, disk storage, magnetic tape drives and IBM 3270 display controllers. ...
channel, a coaxial cable
Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...
using a proprietary protocol, a communications link using Binary Synchronous Communications or IBM's SNA
SNA or Sna may refer to:
Organizations
* Novinite.com (Sofia News Agency), Bulgaria's largest English-language news provider
* Shanni Nationalities Army
* Singapore National Academy, a school in Surabaya, Indonesia
* Sky News Australia, an Austra ...
protocol, but for many DEC, Data General and NCR (and so on) computers there were many visual display suppliers competing against the computer manufacturer for terminals to expand the systems. In fact, the instruction design for the Intel 8008 was originally conceived at Computer Terminal Corporation as the processor for the Datapoint 2200.
From the introduction of the IBM 3270
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971
and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text ...
, and the DEC VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special f ...
(1978), the user and programmer could notice significant advantages in VDU technology improvements, yet not all programmers used the features of the new terminals (backward compatibility
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
in the VT100 and later TeleVideo terminals, for example, with "dumb terminals" allowed programmers to continue to use older software).
Some dumb terminals had been able to respond to a few escape sequences without needing microprocessors: they used multiple printed circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...
s with many integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
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
The VT50 was a CRT-based computer terminal introduced by Digital Equipment Corporation (DEC) in July 1974. It provided a display with 12 rows and 80 columns of upper-case text, and used an expanded set of control characters and forward-only scro ...
, 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 computer
A network host is a computer or other device connected to a computer network. A host may work as a Server (computing), server offering information resources, services, and applications to users or other hosts on the network. Hosts are assigned at ...
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 like the TeleVideo TS-800 could run CP/M-86
CP/M-86 was a version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The system commands are the same as in CP/M-80. Executable files used the relocatable .CMD file format. Digital Research als ...
, blurring the distinction between terminal and Personal Computer.
Another of the motivations for development of the microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
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:
* Lear Siegler ADM-3A and later models
* TeleVideo
TeleVideo Corporation was a U.S. company that achieved its peak of success in the early 1980s producing computer terminals. TeleVideo was founded in 1975 by K. Philip Hwang, a Utah State University, Hanyang University graduate born in South Kore ...
910 to 950 (these models copied ADM3 codes and added several of their own, eventually being copied by Qume and others)
* Digital Equipment Corporation VT52
The VT50 was a CRT-based computer terminal introduced by Digital Equipment Corporation (DEC) in July 1974. It provided a display with 12 rows and 80 columns of upper-case text, and used an expanded set of control characters and forward-only scro ...
and VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special f ...
* Data General D1 to D3 and especially D200 and D210
* Hazeltine Corporation
Hazeltine Corporation was a defense electronics company which is now part of BAE Systems Inc.
History 1924–1986
The company was founded in 1924 by investors to exploit the Neutrodyne patent of Dr. Louis Alan Hazeltine. Headquartered in Gree ...
H1500
* Tektronix
Tektronix, Inc., historically widely known as Tek, is an American company best known for manufacturing test and measurement devices such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment.
Originally an independent ...
4014
* Wyse
WYSE (970 AM) is a radio station located in Canton, North Carolina, that simulcasts WISE's sports format from Asheville, North Carolina. Owned by the Asheville Radio Group subsidiary of Saga Communications, the station is licensed by the Fede ...
W50, W60 and W99
The ANSI X3.64
ANSI escape sequences are a standard for in-band signaling to control cursor location, color, font styling, and other options on video text terminals and terminal emulators. Certain sequences of bytes, most starting with an Escape character#ASC ...
escape code standard produced uniformity to some extent, but significant differences remained. For example, the VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special f ...
, Heathkit H19 in ANSI mode, Televideo 970, Data General D460, and Qume
Qume was a manufacturer of daisy-wheel printers originally located in Hayward, California, later moving to San Jose. Around 1980, it also opened a manufacturing facility in Puerto Rico. It once dominated the daisy-wheel market. As the market for ...
QVT-108 terminals all followed the ANSI standard, yet differences might exist in codes from function keys, what character attributes were available, block-sending of fields within forms, "foreign" character facilities, and handling of printers connected to the back of the screen.
21st century
The term ''Intelligent Terminal'' can now refer to a store (check-out) computer.
Contemporary
While early IBM PCs had single-color green screens, these screens were not terminals. The ''screen'' of a PC did not contain any character generation hardware; all video signals and video formatting were generated by the ''video display card'' in the PC, or (in most graphics modes) by the CPU and software. An IBM PC monitor, whether it was the green monochrome display or the 16-color display, was technically much more similar to an analog TV set
A television set or television receiver, more commonly called the television, TV, TV set, telly, tele, or tube, is a device that combines a tuner, display, and loudspeakers, for the purpose of viewing and hearing television broadcasts, or using ...
(without a tuner) than to a terminal. With suitable software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
a PC could, however, emulate a terminal, and in that capacity it could be connected to a mainframe or minicomputer. The Data General/One could be booted into terminal emulator mode from its ROM. Eventually microprocessor-based personal computers greatly reduced the market demand for conventional terminals.
In the 1990s especially, "thin clients" and X terminal
In computing, an X terminal is a display/input terminal for X Window System client applications. X terminals enjoyed a period of popularity in the early 1990s when they offered a lower total cost of ownership alternative to a full Unix workstati ...
s have combined economical local processing power with central, shared computer facilities to retain some of the advantages of terminals over personal computers:
Today, most PC telnet
Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet control i ...
clients provide emulation of the most common terminal, the DEC VT100, using the ANSI escape code standard X3.64, or could run as X terminals using software such as Cygwin/X
Cygwin/X is an implementation of the X Window System that runs under Microsoft Windows. It is part of the Cygwin project, and is installed using Cygwin's standard setup system. Cygwin/X is free software, licensed under the X11 License.
Cygwin/X w ...
under Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
or X.Org Server
X.Org Server is the free and open-source implementation of the X Window System display server stewarded by the X.Org Foundation.
Implementations of the client-side X Window System protocol exist in the form of ''X11 libraries'', which serve a ...
software under Linux.
Since the advent and subsequent popularization of the personal computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
, few genuine hardware terminals are used to interface with computers today. Using the monitor
Monitor or monitor may refer to:
Places
* Monitor, Alberta
* Monitor, Indiana, town in the United States
* Monitor, Kentucky
* Monitor, Oregon, unincorporated community in the United States
* Monitor, Washington
* Monitor, Logan County, West Vir ...
and keyboard
Keyboard may refer to:
Text input
* Keyboard, part of a typewriter
* Computer keyboard
** Keyboard layout, the software control of computer keyboards and their mapping
** Keyboard technology, computer keyboard hardware and firmware
Music
* Musi ...
, modern operating systems like Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
and the BSD
The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...
derivatives feature virtual consoles, which are mostly independent from the hardware used.
When using a graphical user interface
The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...
(or GUI) like the X Window System
The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems.
X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wit ...
, one's display is typically occupied by a collection of windows associated with various applications, rather than a single stream of text associated with a single process. In this case, one may use a terminal emulator application within the windowing environment. This arrangement permits terminal-like interaction with the computer (for running a command-line interpreter, for example) without the need for a physical terminal device; it can even run multiple terminal emulators on the same device.
Capabilities
Character-oriented terminal
A character-oriented terminal is a type of computer terminal that communicates with its host one character at a time, as opposed to a block-oriented terminal that communicates in blocks of data. It is the most common type of data terminal, because it's easy to implement and program. Connection to the mainframe computer or terminal server
A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication. ...
is achieved via RS-232 serial links, Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
or other proprietary protocol
In telecommunications, a proprietary protocol is a communications protocol owned by a single organization or individual.
Intellectual property rights and enforcement
Ownership by a single organization gives the owner the ability to place restricti ...
s.
Text terminals
A ''text terminal'', or often just ''terminal'' (sometimes ''text console'') is a serial computer interface for text entry and display. Information is presented as an array of pre-selected formed characters. When such devices use a video display such as a cathode-ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictur ...
, they are called a "video display unit
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
The di ...
" or "visual display unit" (VDU) or "video display terminal" (VDT).
The system console
One meaning of system console, computer console, root console, computer operator, 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 ...
is often a text terminal used to operate a computer. Modern computers have a built-in keyboard and display for the console. Some Unix-like operating systems such as Linux and FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...
have virtual consoles to provide several text terminals on a single computer.
The fundamental type of application running on a text terminal is a command-line interpreter or ''shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard ou ...
'', which prompts for commands from the user and executes each command after a press of . This includes Unix shell
A Unix shell is a command-line Interpreter (computing), interpreter or shell (computing), shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting langua ...
s and some interactive programming
Interactive programming is the procedure of writing parts of a program while it is already active. This focuses on the program text as the main interface for a running process, rather than an interactive application, where the program is design ...
environments. In a shell, most of the commands are small applications themselves.
Another important application type is that of the text editor
A text editor is a type of computer program that edits plain text. Such programs are sometimes known as "notepad" software (e.g. Windows Notepad). Text editors are provided with operating systems and software development packages, and can be us ...
. A text editor typically occupies the full area of display, displays one or more text documents, and allows the user to edit the documents. The text editor has, for many uses, been replaced by the word processor
A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features.
Word processor (electronic device), Early word processors were stand-alone devices ded ...
, which usually provides rich formatting features that the text editor lacks. The first word processors used text to communicate the structure of the document, but later word processors operate in a graphical environment and provide a WYSIWYG
In computing, WYSIWYG ( ), an acronym for What You See Is What You Get, is a system in which editing software allows content to be edited in a form that resembles its appearance when printed or displayed as a finished product, such as a printed d ...
simulation of the formatted output. However, text editors are still used for documents containing markup such as DocBook or LaTeX
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
.
Programs such as Telix
Telix is a telecommunications program originally written for DOS by Colin Sampaleanu and released in 1986.
On October 10, 1988 in the release note for Telix 3.10, Sampaleanu announced the creation of 'Exis Inc.'; name used to develop the software ...
and Minicom
Minicom is a text-based modem control and terminal emulator program for Unix-like operating systems, originally written by Miquel van Smoorenburg, and modeled somewhat after the popular MS-DOS program Telix but is open source. Minicom includ ...
control a modem
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
and the local terminal to let the user interact with remote servers. On the Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
, telnet
Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet control i ...
and ssh
The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution.
SSH applications are based on a ...
work similarly.
In the simplest form, a text terminal is like a file. Writing to the file displays the text and reading from the file produces what the user enters. In Unix-like operating systems, there are several character special file
In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow ...
s that correspond to available text terminals. For other operations, there are special escape sequences, control characters and termios
functions that a program can use, most easily via a library such as '' ncurses''. For more complex operations, the programs can use terminal specific ''ioctl
In computing, ioctl (an abbreviation of input/output control) is a system call for device-specific input/output operations and other operations which cannot be expressed by regular system calls. It takes a parameter specifying a request code; th ...
'' system calls. For an application, the simplest way to use a terminal is to simply write and read text strings to and from it sequentially. The output text is scrolled, so that only the last several lines (typically 24) are visible. Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
systems typically buffer
Buffer may refer to:
Science
* Buffer gas, an inert or nonflammable gas
* Buffer solution, a solution used to prevent changes in pH
* Buffering agent, the weak acid or base in a buffer solution
* Lysis buffer, in cell biology
* Metal ion buffer
* ...
the input text until the Enter key is pressed, so the application receives a ready string of text. In this mode, the application need not know much about the terminal. For many interactive applications this is not sufficient. One of the common enhancements is ''command-line editing'' (assisted with such libraries as readline); it also may give access to command history. This is very helpful for various interactive command-line interpreters.
Even more advanced interactivity is provided with ''full-screen'' applications. Those applications completely control the screen layout; also they respond to key-pressing immediately. This mode is very useful for text editors, file managers and web browser
A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on ...
s. In addition, such programs control the color and brightness of text on the screen, and decorate it with underline, blinking and special characters (e.g. box-drawing characters). To achieve all this, the application must deal not only with plain text strings, but also with control characters and escape sequences, which allow moving the cursor
Cursor may refer to:
* Cursor (user interface), an indicator used to show the current position for user interaction on a computer monitor or other display device
* Cursor (databases), a control structure that enables traversal over the records in ...
to an arbitrary position, clearing portions of the screen, changing colors and displaying special characters, and also responding to function keys. The great problem here is that there are many different terminals and terminal emulators, each with its own set of escape sequences. In order to overcome this, special libraries (such as curses) have been created, together with terminal description databases, such as Termcap and Terminfo.
Dumb terminals
Dumb terminals[ are those that can interpret a limited number of control codes (CR, LF, etc.) but do not have the ability to process special escape sequences that perform functions such as clearing a line, clearing the screen, or controlling cursor position. In this context dumb terminals are sometimes dubbed ''glass Teletypes'', for they essentially have the same limited functionality as does a mechanical Teletype. This type of dumb terminal is still supported on modern Unix-like systems by setting the environment variable ''TERM'' to ''dumb''. ''Smart'' or ''intelligent'' terminals are those that also have the ability to process escape sequences, in particular the VT52, VT100 or ANSI escape sequences.
]
Graphical terminals
A graphical terminal can display images as well as text. Graphical terminals are divided into vector-mode terminals, and raster mode.
A vector-mode display directly draws lines on the face of a cathode-ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictur ...
under control of the host computer system. The lines are continuously formed, but since the speed of electronics is limited, the number of concurrent lines that can be displayed at one time is limited. Vector-mode displays were historically important but are no longer used.
Practically all modern graphic displays are raster-mode, descended from the picture scanning techniques used for television
Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
, in which the visual elements are a rectangular array of pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the smal ...
s. Since the raster image is only perceptible to the human eye as a whole for a very short time, the raster must be refreshed many times per second to give the appearance of a persistent display. The electronic demands of refreshing display memory meant that graphic terminals were developed much later than text terminals, and initially cost much more.
Most terminals today are graphical; that is, they can show images on the screen. The modern term for graphical terminal is "thin client
In computer networking, a thin client is a simple (low-performance) computer that has been optimized for establishing a remote connection with a server-based computing environment. They are sometimes known as ''network computers'', or in th ...
". A thin client typically uses a protocol like X11 for Unix terminals, or RDP for Microsoft Windows. The bandwidth needed depends on the protocol used, the resolution, and the color depth
Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, or the number of bits used for each color component of a single pixel. When referring to ...
.
Modern graphic terminals allow display of images in color, and of text in varying sizes, colors, and font
In metal typesetting, a font is a particular size, weight and style of a typeface. Each font is a matched set of type, with a piece (a "sort") for each glyph. A typeface consists of a range of such fonts that shared an overall design.
In mod ...
s (type faces).
In the early 1990s, an industry consortium attempted to define a standard, AlphaWindows AlphaWindows was a proposed industry standard from the Display Industry Association (an industry consortium in California) in the early 1990s that would allow a single CRT screen to implement multiple windows, each of which was to behave as a distin ...
, that would allow a single CRT screen to implement multiple windows, each of which was to behave as a distinct terminal. Unfortunately, like I2O
Intelligent Input/Output (I2O) is a defunct computer input/output (I/O) specification. I2O was originally designed to make use of the Intel i960 microprocessor as the I/O offload engine, bringing channel I/O to the PC. I2O emerged from Intel in ...
, this suffered from being run as a closed standard: non-members were unable to obtain even minimal information and there was no realistic way a small company or independent developer could join the consortium. Possibly because of this the standard disappeared without a trace.
Emulation
A terminal emulator is a piece of software that emulates a text terminal. In the past, before the widespread use of local area network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
s and broadband internet access, many computers would use a serial access program to communicate with other computers via telephone line
A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or ot ...
or serial device.
When the first Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc., Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and ...
was released, a program called MacTerminal
MacTerminal was the first telecommunications and terminal emulation application software program available for the classic Mac OS. MacTerminal enabled users to connect via modem or serial port to bulletin board systems and online services (e. ...
was used to communicate with many computers, including the IBM PC
The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
.
Dec Terminal was one of the first terminal programs for the popular Altair
Altair is the brightest star in the constellation of Aquila and the twelfth-brightest star in the night sky. It has the Bayer designation Alpha Aquilae, which is Latinised from α Aquilae and abbreviated Alpha Aql or ...
.
The Win32 console
Windows Console is the infrastructure for console applications in Microsoft Windows. An instance of a Windows Console has a screen buffer and an input buffer. It allows console apps to run inside a window or in hardware text mode (so as to oc ...
on Windows does not emulate a physical terminal that supports escape sequences so SSH and Telnet programs (for logging in textually to remote computers) for Windows, including the Telnet program bundled with some versions of Windows, often incorporate their own code to process escape sequences.
The terminal emulators on most Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
systems—such as, for example, gnome-terminal
GNOME Terminal is a terminal emulator for the GNOME desktop environment written by Havoc Pennington and others. Terminal emulators allow users to access a UNIX shell while remaining on their graphical desktop.
Features
GNOME Terminal (gnome-term ...
, qterminal, xterm
In computing, xterm is the standard terminal emulator for the X Window System. It allows users to run programs which require a command-line interface.
If no particular program is specified, xterm runs the user's shell. An X display can show ...
, and Terminal.app
This is a list of macOS built-in apps and system components.
Applications
App Store
The Mac App Store is macOS's digital distribution platform for macOS apps, created and maintained by Apple Inc. based on the iOS version, the platform was an ...
—do emulate physical terminals including support for escape sequences; e.g., xterm can emulate the VT220
The VT220 is a computer terminal introduced by Digital Equipment Corporation (DEC) in November 1983. The VT240 added monochrome ReGIS vector graphics support to the base model, while the VT241 did the same in color. The 200 series replaced the s ...
and Tektronix 4010
The Tektronix 4010 series was a family of text-and-graphics computer terminals based on storage-tube technology created by Tektronix. Several members of the family were introduced during the 1970s, the best known being the 11-inch 4010 and 19-inc ...
hardware terminals.
Modes
Terminals can operate in various modes, relating to when they send input typed by the user on the keyboard to the receiving system (whatever that may be):
* Character mode (a.k.a. character-at-a-time mode): In this mode, typed input is unbuffered and sent immediately to the receiving system.
* Line mode (a.k.a. line-at-a-time mode): In this mode, the terminal is buffered, provides a local line editing function, and sends an entire input line, after it has been locally edited, when the user presses an, e.g., , , key. A so-called "line mode terminal" operates solely in this mode.
* Block mode (a.k.a. screen-at-a-time mode): In this mode (also called block-oriented), the terminal is buffered and provides a local full-screen data function. The user can enter input into multiple fields in a form on the screen (defined to the terminal by the receiving system), moving the cursor around the screen using keys such as and the arrow keys and performing editing functions locally using , , and so forth. The terminal sends only the completed form, consisting of all the data entered on the screen, to the receiving system when the user presses an key.
There is a distinction between the and the keys. In some multiple-mode terminals, that can switch between modes, pressing the key when ''not'' in block mode does not do the same thing as pressing the key. Whilst the key will cause an input line to be sent to the host in line-at-a-time mode, the key will rather cause the terminal to transmit the contents of the character row where the cursor is currently positioned to the host, host-issued prompts and all. Some block-mode terminals have both an and local cursor moving keys such as and .
Different computer operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
s require different degrees of mode support when terminals are used as computer terminals. The POSIX terminal interface
The POSIX terminal interface is the generalized abstraction, comprising both an application programming interface for programs, and a set of behavioural expectations for users of a terminal, as defined by the POSIX standard and the Single Unix Spe ...
, as provided by Unix and POSIX-compliant operating systems, does not accommodate block-mode terminals at all, and only rarely requires the terminal ''itself'' to be in line-at-a-time mode, since the operating system is required to provide canonical input mode, where the terminal device driver in the operating system ''emulates'' local echo in the terminal, and performs line editing functions at the host end. Most usually, and especially so that the host system can support non-canonical input mode, terminals for POSIX-compliant systems are always in character-at-a-time mode. In contrast, IBM 3270 terminals connected to MVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers. IBM developed MVS, along with OS/VS1 and SVS, as a successor to OS/360. It is unrelated ...
systems are always required to be in block mode.
Block-oriented terminal
A block-oriented terminal or block mode terminal is a type of computer terminal that communicates with its host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
in blocks of data, as opposed to a character-oriented terminal that communicates with its host one character at a time. A block oriented terminal may be card-oriented, display oriented, keyboard-display, keyboard-printer, printer or some combination.
Display
The IBM 3270 is perhaps the most familiar implementation of a block-oriented display terminal, but most mainframe computer manufacturers and several other companies produced them. The description below is in terms of the 3270, but similar considerations apply to other types.
Block-oriented terminals typically incorporate a buffer
Buffer may refer to:
Science
* Buffer gas, an inert or nonflammable gas
* Buffer solution, a solution used to prevent changes in pH
* Buffering agent, the weak acid or base in a buffer solution
* Lysis buffer, in cell biology
* Metal ion buffer
* ...
which stores one screen or more of data, and also stores data attributes, not only indicating appearance (color, brightness, blinking, etc.) but also marking the data as being enterable by the terminal operator vs. ''protected'' against entry, as allowing the entry of only numeric information vs. allowing any characters, etc. In a typical application the host sends the terminal a preformatted panel
Panel may refer to:
Arts and media Visual arts
* Panel (comics), a single image in a comic book, comic strip or cartoon; also, a comic strip containing one such image
*Panel painting, in art, either one element of a multi-element piece of art ...
containing both static data and fields into which data may be entered. The terminal operator keys data, such as updates in a database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...
entry, into the appropriate fields. When entry is complete (or ENTER or PF key pressed on 3270s), a block of data, usually just the data entered by the operator (modified data), is sent to the host in one transmission. The 3270 terminal buffer (at the device) could be updated on a single character basis, if necessary, because of the existence of a "set buffer address order" (SBA), that usually preceded any data to be written/overwritten within the buffer. A complete buffer could also be read or replaced using the READ BUFFER
command or WRITE
command (unformatted or formatted in the case of the 3270).
Block-oriented terminals cause less system load on the host and less network traffic than character-oriented terminals. They also appear more responsive to the user, especially over slow connections, since editing within a field is done locally rather than depending on echoing
In audio signal processing and acoustics, an echo is a reflection (physics), reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from t ...
from the host system.
Early terminals had limited editing capabilities – 3270 terminals, for example, only could check entries as valid numerics. Subsequent "smart" or "intelligent" terminals incorporated microprocessors and supported more local processing.
Programmers of block-oriented terminals often used the technique of storing ''context'' information for the transaction in progress on the screen, possibly in a hidden field, rather than depending on a running program to keep track of status. This was the precursor of the HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScri ...
technique of storing context in the URL
A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifie ...
as data to be passed as arguments to a CGI program.
Unlike a character-oriented terminal, where typing a character into the last position of the screen usually causes the terminal to scroll down one line, entering data into the last screen position on a block-oriented terminal usually causes the cursor to ''wrap''— move to the start of the first enterable field. Programmers might "protect" the last screen position to prevent inadvertent wrap. Likewise a protected field following an enterable field might lock the keyboard and sound an audible alarm if the operator attempted to enter more data into the field than allowed.
Common block oriented terminals
Hard-copy
*IBM 1050
IBM 1050 Data Communications System is a computer terminal subsystem to send data to and receive data from another 1050 subsystem or IBM computer in the IBM 1400, IBM 7000 or System/360 series. It first became available in 1963 and was used wi ...
*IBM 2740
The IBM 2741 is a printing computer terminal that was introduced in 1965. Compared to the teletypewriter machines that were commonly used as printing terminals at the time,
the 2741 offers 50% higher speed, much higher quality printing, quieter op ...
Remote job entry
*IBM 2770
The IBM 2780 and the IBM 3780 are devices developed by IBM to perform remote job entry (RJE) and other batch functions over telephone lines; they communicate with the mainframe via Binary Synchronous Communications (BSC or Bisync) and replaced ...
* IBM 2780
*IBM 3770
The IBM 2780 and the IBM 3780 are devices developed by IBM to perform remote job entry (RJE) and other batch functions over telephone lines; they communicate with the mainframe via Binary Synchronous Communications (BSC or Bisync) and replaced ...
* IBM 3780
Display
See also
* Blit (computer terminal)
* Data terminal equipment
* IBM 3101 The IBM 3101 ASCII Display Station, and IBM's subsequent products, the 3151/315X and 3161/316X, are display terminals with asynchronous serial communication (start-stop signaling) that were used with a variety of IBM and non-IBM computers during the ...
* Micro-Term ERGO-201
The Micro-Term ERGO-201 is a computer terminal produced in 1983 as part of the ERGO series of computers manufactured by Micro-Term Incorporated, located in St. Louis, MO. It consists of a monitor and a keyboard. The monitor contains the mother ...
* Minitel
* Text user interface
In computing, text-based user interfaces (TUI) (alternately terminal user interfaces, to reflect a dependence upon the properties of computer terminals and not just text), is a retronym describing a type of user interface (UI) common as an ear ...
* TV Typewriter
The TV Typewriter is a video terminal that could display two pages of 16 lines of 32 upper case characters on a standard television set. The design, by Don Lancaster, appeared on the cover of ''Radio-Electronics'' magazine in September 1973.
The ...
* Videotex
Videotex (or interactive videotex) was one of the earliest implementations of an end-user information system. From the late 1970s to early 2010s, it was used to deliver information (usually pages of text) to a user in computer-like format, typi ...
* Virtual console (PC)
A virtual console (VC) – also known as a virtual terminal (VT) – is a conceptual combination of the keyboard and display for a computer user interface. It is a feature of some Unix-like operating systems such as Linux, BSD, illumos, Unix ...
* Communication endpoint
A communication endpoint is a type of communication network node. It is an interface exposed by a communicating party or by a communication channel. An example of the latter type of a communication endpoint is a publish-subscribe topic or a grou ...
* End system
In networking jargon, a computer, phone, or internet of things device connected to a computer network is sometimes referred to as an end system or end station, because it sits at the edge of the network. The end user directly interacts with an ...
* Node (networking)
In telecommunications networks, a node (, ‘knot’) is either a redistribution point or a communication endpoint. The definition of a node depends on the network and protocol layer referred to. A physical network node is an electronic device ...
* Terminal capabilities In computing and telecommunications, the capabilities of a terminal are various terminal features, above and beyond what is available from a pure teletypewriter, that host systems (and the programs that run on them) can make use of. They are (mainl ...
* Terminal emulator
A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote termin ...
* Visual editor
A visual editor is computer software for editing text files using a textual or graphical user interface that normally renders the content (text) in accordance with embedded markup code, e.g., HTML, Wikitext, rather than displaying the raw text. E ...
* VT05
:''"VT-05" can also refer to .''
The VT05 is the first free-standing CRT computer terminal from Digital Equipment Corporation introduced in 1970. Famous for its futuristic styling, the VT05 presents the user with an upper-case-only ASCII charac ...
Notes
References
*
*
*
*
*
*
*
*
External links
The Terminals Wiki
an encyclopedia of computer terminals.
The TTY demystified
* {{webarchive , url=https://web.archive.org/web/20100523190056/http://www.cs.utk.edu/~shuford/terminal , date=May 23, 2010 , title=Video Terminal Information
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)
epocalc list of Computer Terminals
User interfaces
History of human–computer interaction
Operating system technology
Block-oriented terminal