Misplaced Pages

#641358

64-616: There were several variants, including the SuperBrain II (released in 1982), SuperBrain II Jr., "QD" (quad density disk drives) and "SD" (super density) models. Intertec also released a similar looking dumb terminal , the Intertube , and smart terminal, the Emulator . The SuperBrain is notable for being at the user end of the first Kermit connection in 1981. The machine was practical and useful in

128-401: A computer or a computing system. 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. Teleprinters were used as early-day hard-copy terminals and predated the use of a computer screen by decades. The computer would typically transmit a line of data which would be printed on paper, and accept

192-445: A rich client (also called a heavy , fat or thick client ) is a computer (a " client " in client–server network architecture) that typically provides rich functionality independent of the central server . This kind of computer was originally known as just a "client" or "thick client," in contrast with " thin client ", which describes a computer heavily dependent on a server's applications. A rich client may be described as having

256-416: A rich user interaction . While a rich client still requires at least a periodic connection to a network or central server , it is often characterised by the ability to perform many functions without a connection. In contrast, a thin client generally does as little processing as possible on the client, relying on access to the server each time input data needs to be processed or validated. The designer of

320-425: A Superbrain to analyse samples from The Thing from which he estimates that it will take over the world in about three years. This microcomputer - or microprocessor -related article is a stub . You can help Misplaced Pages by expanding it . Dumb terminal A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from,

384-478: A built-in keyboard and display for the console. Some Unix-like operating systems such as Linux and FreeBSD 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 , which prompts for commands from the user and executes each command after a press of Return . This includes Unix shells and some interactive programming environments. In

448-416: A client–server application decides which parts of the task should be executed on the client, and which on the server. This decision can crucially affect the cost of clients and servers, the robustness and security of the application as a whole, and the flexibility of the design for later modification or porting . The characteristics of the user interface often force the decision on a designer. For instance,

512-412: A drawing package could require the download of an initial image from a server, and allow all edits to be made locally, returning the revised drawing to the server upon completion. This would require a rich client and might be characterised by a long delay to start and stop (while a whole complex drawing was transferred), but quick to edit. Conversely, a thin client could download just the visible parts of

576-430: 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

640-530: A green or amber screen. Typically terminals communicate with the computer via a serial port via a null modem cable, often using an EIA RS-232 or RS-422 or RS-423 or a current loop serial interface. IBM systems typically communicated over a Bus and Tag channel, a coaxial cable using a proprietary protocol, a communications link using Binary Synchronous Communications or IBM's SNA protocol, but for many DEC, Data General and NCR (and so on) computers there were many visual display suppliers competing against

704-610: A keyboard in 1941, as did the 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 a row of display lamps for results. In 1956, the Whirlwind Mark ;I computer became the first computer equipped with a keyboard-printer combination with which to support direct input of data and commands and output of results. That device

SECTION 10

#1733084712642

768-457: A library such as ncurses . For more complex operations, the programs can use terminal specific ioctl 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 systems typically buffer the input text until the Enter key

832-632: A line of data from a keyboard over a 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 and workstation computer systems, with the computer handling character generation and outputting to a 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 cards or paper tape for input; with

896-607: 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 , predecessor to the IBM 3250 and IBM 5080, and IBM 2260 , predecessor to the IBM 3270 , introduced with System/360 in 1964. Most terminals were connected to minicomputers or mainframe computers and often had

960-594: 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 . Today few if any dedicated computer terminals are being manufactured, as time sharing on large computers has been replaced by personal computers, handheld devices and workstations with graphical user interfaces. User interactions with servers use either software such as Web browsers , or terminal emulators, with connections over high-speed networks. The console of Konrad Zuse 's Z3 had

1024-593: 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

1088-472: A shell, most of the commands are small applications themselves. Another important application type is that of the text editor . 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 , which usually provides rich formatting features that the text editor lacks. The first word processors used text to communicate

1152-455: A standard, AlphaWindows , that would allow a single CRT screen to implement multiple windows, each of which was to behave as a distinct terminal. Unfortunately, like I2O , 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. An intelligent terminal does its own processing, usually implying

1216-446: 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

1280-571: A thin client environment. In more recent years, the Internet has tended to drive the thin client model despite the prodigious processing power that a modern PC has available. Probably the thinnest clients, sometimes called "ultra thin," are remote desktop applications, e.g. the Citrix products, and Microsoft 's Remote Desktop Services , which effectively allow applications to run on a centrally-hosted virtual PC and copy keystrokes and screen images between

1344-456: A typical application the host sends the terminal a preformatted panel containing both static data and fields into which data may be entered. The terminal operator keys data, such as updates in a database 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

SECTION 20

#1733084712642

1408-402: Is " thin client ". 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 . Modern graphic terminals allow display of images in color, and of text in varying sizes, colors, and fonts (type faces). In the early 1990s, an industry consortium attempted to define

1472-406: 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 , they are called a " video display unit " or "visual display unit" (VDU) or "video display terminal" (VDT). The system console is often a text terminal used to operate a computer. Modern computers have

1536-522: Is a type of computer terminal that communicates with its 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. 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

1600-495: Is achieved via RS-232 serial links, Ethernet or other proprietary protocols . Character-oriented terminals can be "dumb" or "smart". 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

1664-462: Is in terms of the 3270, but similar considerations apply to other types. Block-oriented terminals typically incorporate a 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

1728-400: 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 , in which the visual elements are a rectangular array of pixels . Since the raster image is only perceptible to

1792-444: 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

1856-428: 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 browsers . 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,

1920-500: 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

1984-742: The Intel 8080 . This made them inexpensive and they quickly became extremely popular input-output devices on many types of computer system, often replacing earlier and more expensive printing terminals. After 1970 several suppliers gravitated to a set of common standards: The experimental era of serial VDUs culminated with the VT100 in 1978. By the early 1980s, there were dozens of manufacturers of terminals, including Lear-Siegler , ADDS , Data General, DEC , Hazeltine Corporation , Heath/Zenith , Hewlett-Packard , IBM, TeleVideo , Volker-Craig, and Wyse , many of which had incompatible command sequences (although many used

Intertec Superbrain - Misplaced Pages Continue

2048-498: The VT220 terminal strongly influenced the Model M 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

2112-573: The ASR Teletype models, included a paper tape reader and punch which could record output such as a program listing. The data on the tape could be re-entered into the computer using the tape reader on the teletype, or printed to paper. Teletypes used the current loop interface that was already used in telegraphy. A less expensive Read Only (RO) configuration was available for the Teletype. Custom-designs keyboard/printer terminals that came later included

2176-629: The TeleVideo TS-800 could run CP/M-86 , blurring the distinction between terminal and Personal Computer. 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: Fat client In computer networking ,

2240-446: 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 displays . 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 2400 bit/s . Similarly,

2304-642: The application must deal not only with plain text strings, but also with control characters and escape sequences, which allow moving the cursor 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. A block-oriented terminal or block mode terminal

2368-556: 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 , and the DEC VT100 (1978), the user and programmer could notice significant advantages in VDU technology improvements, yet not all programmers used

2432-588: The development of the VDU were the Univac Uniscope and the IBM 2260 , both in 1964. These were block-mode terminals designed to display a page at a time, using proprietary protocols; in contrast to character-mode devices, they enter data from the keyboard into a display buffer rather than transmitting them immediately. In contrast to later character-mode devices, the Uniscope used synchronous serial communication over an EIA RS-232 interface to communicate between

2496-473: 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

2560-423: 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

2624-445: The drawing at the beginning and send each change back to the server to update the drawing. This might be characterised by a short start-up time, but a tediously slow editing process. The original server clients were simple text display terminals including Wyse VDUs , and rich clients were generally not used until the increase in PC usage. The original driving force for thin client computing

Intertec Superbrain - Misplaced Pages Continue

2688-554: 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 systems the termcap or terminfo files, the stty utility, and the TERM environment variable would be used; in Data General's Business BASIC software, for example, at login-time

2752-615: 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. Very early VDUs with cursor addressibility included the VT05 and the Hazeltine 2000 operating in character mode, both from 1970. Despite this capability, early devices of this type were often called "Glass TTYs". Later,

2816-456: The features of the new terminals ( backward compatibility 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 boards with many integrated circuits ; the single factor that classed

2880-548: 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 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

2944-505: The host computer for its processing power is called a " dumb terminal " or a thin client . 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. A personal computer can run terminal emulator software that replicates functions of

3008-429: 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

3072-806: The last revision (the DECwriter IV of 1982) abandoning the classic teletypewriter form for one more resembling a desktop printer. 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 like MIT ; computers used in academia, government and business, sold under brand names like DEC , ERA , IBM and UNIVAC ; military computers supporting specific defence applications such as ballistic missile warning systems and radar/air defence coordination systems like BUIC and SAGE . Two early landmarks in

3136-431: 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 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

3200-404: The multiplexer and the host, while the 2260 used either a channel connection or asynchronous serial communication between the 2848 and the host. The 2265, related to the 2260, also used asynchronous serial communication. The Datapoint 3300 from Computer Terminal Corporation , announced in 1967 and shipped in 1969, was a character-mode device that emulated a Model 33 Teletype . This reflects

3264-430: The office environment, but somewhat limited until the arrival of the first 5 MB hard drive in one of the floppy drive bays. This was soon replaced by the 10 MB hard drive. Up to 255 CompuStar workstations could be daisy-chained together via DC-37 "Chaining Adaptor" parallel ports to share the "central disk system" (one of the three hard drive peripheral options below). Each computer, or VPU (Video Processing Unit),

SECTION 50

#1733084712642

3328-407: The operator attempted to enter more data into the field than allowed. 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 under control of the host computer system. The lines are continuously formed, but since the speed of electronics

3392-468: 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. A text terminal , or often just terminal (sometimes text console )

3456-413: 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

3520-415: 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 files 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

3584-441: The speed of remote batch terminals had improved to 4800 bit/s at the beginning of the decade and 19.6 kbps by the end of the decade, with higher speeds possible on more expensive 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 . A terminal that depends on

3648-489: The structure of the document, but later word processors operate in a graphical environment and provide a WYSIWYG simulation of the formatted output. However, text editors are still used for documents containing markup such as DocBook or LaTeX . Programs such as Telix and Minicom control a modem and the local terminal to let the user interact with remote servers. On the Internet , telnet and ssh work similarly. In

3712-504: 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 technique of storing context in the URL 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

3776-470: The term "glass TTY" tended to be restrospectively narrowed to devices without full cursor addressibility. 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 , and VT100 . These devices used no complicated CPU , instead relying on individual logic gates , LSI chips, or microprocessors such as

3840-417: The year 2000, the hardware computer terminal was nearly obsolete. 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 is easy to implement and program. Connection to the mainframe computer or terminal server

3904-588: Was a Friden Flexowriter , which would continue to serve this purpose on many other early computers well into the 1960s. Early user terminals connected to computers were, like the Flexowriter, electromechanical teleprinters /teletypewriters (TeleTYpewriter, TTY), such as the Teletype Model ;33 , originally used for telegraphy ; early Teletypes were typically configured as Keyboard Send-Receive (KSR) or Automatic Send-Receive (ASR). Some terminals, such as

SECTION 60

#1733084712642

3968-604: Was assigned a unique number from 1 to 255 by setting an eight-position DIP switch . The brazilian company Prológica introduced the Sistema 700 in 1981, based on the SuperBrain and with similar characteristics. The Superbrain can be seen in two episodes of Knight Rider : one in Season 1, Episode 10, "The Final Verdict" (1982), and the second in Season 1, Episode 18, "White Bird" (1983). In John Carpenter’s The Thing , Dr. Blair uses

4032-495: 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

4096-480: Was often cost; at a time when CRT terminals and PCs were relatively expensive, the thin-client–server architecture enabled the ability to deploy the desktop computing experience to many users. As PC prices decreased, combined with a drop in software licensing costs, rich client–server architectures became more attractive. For users, the rich client device provided a more-responsive platform and often an improved Graphical User Interface (GUI) than what could be achieved in

#641358