VT100
 | |
| Manufacturer | DEC |
|---|---|
| Type | Computer terminal |
| Release date | 1978 |
| CPU | Intel 8080 |
| Memory | 3 KB RAM 8 KB ROM 175 byteNVRAM |
| Display | 12 in (30 cm)CRT 80x24 or 132x14 characters |
| Sound | Speaker (in keyboard) |
| Input | 83-key detachablekeyboard |
| Connectivity | RS-232serial (optional)20 mA current loop |
| Mass | Monitor: 30 lb (14 kg) Keyboard: 4.5 lb (2.0 kg) |
| Predecessor | VT50 |
| Successor | VT220 |
TheVT100is a videoterminal,introduced in August 1978 byDigital Equipment Corporation(DEC). It was one of the first terminals to supportANSI escape codesfor cursor control and other tasks, and added a number of extended codes for special features like controlling the status lights on the keyboard. This led to rapid uptake of the ANSI standard, which became thede facto standardfor hardware video terminals and laterterminal emulators.
The VT100 series, especially the VT102, was extremely successful in the market, and made DEC the leading terminal vendor at the time. The VT100 series was replaced by theVT200 seriesstarting in 1983, which proved equally successful. Ultimately, over six million terminals in the VT series were sold, based largely on the success of the VT100.[1]
Description
[edit]DEC's first video terminal was theVT05(1970), succeeded by theVT50(1974), and soon upgraded to theVT52(1975). The VT52 featured a text display with 80 columns and 24 rows, bidirectional scrolling, and a custom control protocol that allowed the cursor to be moved about the screen. These "smart terminals" were a hit due both to their capabilities and to their ability to be run over inexpensive serial links, rather than custom proprietary connections as in the case of systems like theIBM 3270,which generally required expensive controllers for distributed applications. In contrast, "dumb terminals" or "glass teletypes" like theADM-3A(1976) lacked advanced features such as full cursor addressability, and competed mostly on lowest possible hardware cost.
The VT100 was introduced in August 1978, replacing the VT50/VT52 family. Like the earlier models, it communicated with itshostsystem over serial lines at a minimum speed of 50 bit/s, but increased the maximum speed to 19,200 bit/s, double that of the VT52.[2]: 1–3 The terminal provided an option for "smooth scrolling", whereby displayed lines of text were moved gradually up or down the screen to make room for new lines, instead of advancing in sudden "jumps". This made it easier to scan or read the text, although it somewhat slowed down the maximum data rate.[2]: 2–16
The major internal change was the control protocol. Unlike the VT50/52's proprietary cursor control language, the VT100 was based on the newly emergingANSI X3.64standard for command codes.[a]At the time, some computer vendors[who?]had suggested that the new standard was beyond thestate of the artand could not be implemented at a reasonable price. The introduction of low-costmicroprocessorsand the ever-falling cost ofcomputer memoryoffered greatly expanded capabilities, and the VT100 used the newIntel 8080as its internalprocessor.[3]In addition, the VT100 providedbackwards compatibilityfor VT52-compatible software, by also supporting the older control sequences.[4] Other improvements beyond the VT52 included a 132-column mode, and a variety of "graphic renditions" including blinking, bolding,reverse video,underlining, and lines of double-sized or double-width characters. The VT100 also introduced an additionalbox-drawing character setcontaining various pseudographics that allowed the drawing of on-screen forms.
All configuration setup of the VT100 was accomplished using interactive displays presented on the screen; the setup data was stored innon-volatile memorywithin the terminal. Maintainability was also significantly improved, since a VT100 could be quickly dismantled into replaceable modules.
The VT100's internal layout can be split into two boards for functionality, not including the VT100's optional boards you can purchase. There is a board called the video monitor board which is used for things like adjusting the CRT on the terminal itself. This board is responsible for adjusting the CRT in the case that the electron beam is offset.[5]The terminal controller board is what handles the terminal logic, and includes a multitude of chips such as DEC's rebranding of the Intel 8080.
In 1983, the VT100 was replaced by the more powerful VT200 series terminals such as theVT220.
Options
[edit]The VT100 has various third party and first party boards designed to enhance the capabilities of the device. Most notable of these from DEC themselves are theVT1XX-AB(Advanced Video Option) and theVT1XX-AA(20 mA Current Loop Option). The cards' capabilities and existence are described in Chapter 4 of the VT100 User Guide.[4]
Variants
[edit]
The VT100 was the first of Digital's terminals to be based on an industry-standard microprocessor, theIntel 8080.Options could be added to the terminal to support an external printer, additional graphic renditions, and more character memory. The last option, known as the "Advanced Video Option" or AVO, allowed the terminal to support a full 24 lines of text in 132-column mode, increasing from the 14 lines of the unexpanded model when used in 132-column mode. The VT100 became a platform on which Digital constructed several related hardware products.
The VT101 and VT102 were cost-reduced, non-expandable follow-on versions. The VT101 was essentially a base-model VT100, while the VT102 came standard with the AVO and serial printer port options pre-installed. The VT105 contained a simple graphics subsystem known aswaveform graphicswhich was mostly compatible with same system in the earlierVT55.This system allowed two mathematical functions to be drawn to the screen superimposed over the normal text display, allowing text and graphics to be mixed to produce charts and similar output.[6]The VT125 added an implementation of the byte-efficient Remote Graphic Instruction Set (ReGIS), which used custom ANSI codes to send graphics commands to the terminal, rather than requiring the terminal to be set to a separate less-efficientgraphics modelike the VT105.
The VT131 addedblock modesupport, allowing a form to be sent to the terminal and filled in locally by the user, and then sending the contents of the fields in the form back to the host when the form is filled in.[7]
The VT100 form factor left significant physical space in the case for expansion, and DEC used this to produce several all-in-one stand-aloneminicomputersystems. The VT103 included a cardcage and 4×4 (8-slot)Q-Busbackplane, sufficient to configure a small 16-bitLSI-11microcomputer system within the case,[8]: pp65–72 and supported an optional dualTU58DECtape II block-addressable cartridge tape drive[8]: pp73–80 which could be used like a very slow disk drive. TheVT180(codenamed "Robin" ) added a single-board microcomputer using aZilog Z80to run theCP/Moperating system. TheVT278 (DECmate)added a smallPDP-8processor, allowing the terminal to run Digital'sWPS-8word processing software.
See also
[edit]References
[edit]- ^"VT 510/520 Video Display Terminal"(PDF).Boundless Technologies.Archived(PDF)from the original on 2015-02-05.
- ^abVT100 Series Technical Manual(PDF).Digital Equipment Corporation. 1979.Archived(PDF)from the original on 2020-01-01.Retrieved2022-04-22.
- ^Shuford, Richard S. (2005),DEC Video Terminals—The VT100 and Its Successors,archivedfrom the original on 2022-04-22,retrieved2015-08-22
- ^ab"VT100 User Guide".Digital Equipment Corporation. August 1978. EK-VT100-UG-001.
- ^VT101 Series Pocket Service Guide(PDF).Digital Equipment Corporation. September 1981. EK-VT101-PS-001.
- ^VT55 Programmer's Manual(PDF).Digital Equipment Corporation.February 1977. AA-4949A-TC.Archived(PDF)from the original on 2022-03-21.Retrieved2022-04-21.
- ^VT131 Video Terminal User Guide(PDF)(2nd ed.).Digital Equipment Corporation.October 1981. EK-VT131-UG-002.Archived(PDF)from the original on 2022-07-11.Retrieved2022-04-21.
- ^abVT103 LSI-11 Video Terminal User's Guide(PDF)(First ed.).Digital Equipment Corporation.September 1979. EK-VT103-UG-001.Archived(PDF)from the original on 2011-08-14.Retrieved2014-05-03.
- Notes
- ^A similar standard was being organized as ECMA-48, which was fairly similar to X3.64. The two standards were later merged in ISO 6429.
External links
[edit]- DEC video terminal historyArchive
- VT100 user guide
- VT100 Series Technical Manual
- ECMA-48
- TheDECcategory at the Terminals Wiki
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