VT220
DE-9 serial printer port | |
Predecessor | VT100 |
---|---|
Successor | VT320 |
The VT220 is a computer terminal introduced by Digital Equipment Corporation (DEC) in November 1983.[1][2] 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 successful VT100 series, providing more functionality in a much smaller unit with a much smaller and lighter keyboard. Like the VT100, the VT200 series implemented a large subset of ANSI X.364. Among its major upgrades was a number of international character sets, as well as the ability to define new character sets.
The VT200 series was extremely successful in the market. Released at $1,295,[3] but later priced at $795, the VT220 offered features, packaging and price that no other serial terminal could compete with at the time. In 1986, DEC shipped 165,000 units, giving them a 42% market share, double that of the closest competitor, Wyse. Competitors adapted by introducing similar models at lower prices, leading DEC to do the same by releasing the less-expensive $545 VT300 series in 1987. By that time, DEC had shipped over one million VT220s.[4]
Hardware
The VT220 improved on the earlier VT100 series of terminals with a redesigned keyboard, much smaller physical packaging, and a much faster microprocessor, DEC's own
The VT100s, like the
The
The VT200s were the last DEC terminals to provide a
Software
The VT220 was designed to be compatible with the
Glyphs were formed within a 10 by 10 grid. The terminal shipped with a total of 288 characters in its ROM, each one formed from an 8 by 10 pixel glyph. Using only 8 of the columns left space between the characters. The characters included the 96 printable ASCII characters, 67 Display Controls, 32 DEC Special Graphics, and a backward question mark used to represent undefined characters.
The VT200s included the ability to make minor changes to the character set using the National Replacement Character Set (NRCS) concept. When operating on an 8-bit clean link up to 256 character codes were available, which included a full set of European characters. But when operating on a typical 7-bit link, only 128 were available, and only 96 of these produced display output as the rest were control characters. This was not enough characters to handle all European languages. Most terminals solved this by shipping multiple complete character sets in ROM, but there was a cost in doing so.
DEC's solution to this problem, NRCS, allowed individual characters glyphs in the base set of 96 7-bit characters to be swapped out. For instance, the British set made a single substitution, replacing the US's hash character, #, with the pound sign, £. The terminal included 14 such replacement sets, most of which swapped out about a dozen characters.[5] This eliminated the need to ship 14 versions of the terminal, or to include 14 different 7-bit character sets in ROM.
Additionally, the VT200s allowed for another 96 characters in the
Escape Key controversy
Prior to the VT220, if an
Legacy
In 1983-1984, during the design phase of the IBM Model M keyboard, the VT220 was a new and very popular product. IBM's design team chose[9] to emulate its LK201 keyboard layout. Key innovations that IBM copied were the inverted-T shape of the arrow cluster, the navigation keys above it, and the numeric keypad off to its right. Eventually the popularity of the IBM PC would lead to the Model M layout becoming standardized by ANSI and ISO. Through those standards, minor variations of the VT220's keyboard layout have dominated keyboard design ever since.
See also
- ANSI escape code
- Rainbow 100
- Vttest - VT100 / VT220 / XTerm Test Utility
References
- ^ Richard Shuford (1995–2005). "DEC Video Terminals". Archived from the original on 2009-06-05.
- ^ "VT220 Programmer Reference Manual". Digital Equipment Corporation. August 1984.
- ^ Bartimo, Jim (21 November 1983). "DEC Unveils New Design In Successor To VT100". Computerworld. pp. 1, 6. Retrieved 26 January 2023.
- ^ Bright, David (31 August 1987). "DEC VT320 late, but low price surprises". Computerworld. p. 16. Retrieved 26 January 2023.
- ^ "National Replacement Character Set (NRCS)"[sic]
- ^ VT320 Soft Character Sets
- HARDCOPY. p. 170.
- ^ "VT220 ESCAPE key". Computerworld. March 18, 1985. p. 68.
you have to go hunt for the VT220 ESCAPE key
- ^ "Why I Still Use a 34-Year-Old IBM Model M Keyboard". Retrieved 2021-04-19.