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67-664: 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 the VT200 series starting 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. DEC's first video terminal was the VT05 (1970), succeeded by

134-421: 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

201-577: A 16-pixel high marker will be drawn. Sold alone, the VT55 was priced at $ 2,496, equivalent to $ 15,421 in 2023. Like other models of the VT50 series, the terminal could be equipped with an optional wet-paper printer in a panel on the right of the screen. This added $ 800 equivalent to $ 4,943 in 2023 to the price. DEC also offered VT55 in a package with a small model of the PDP-11 to create one model of

268-470: A cardcage and 4×4 (8-slot) Q-Bus backplane, sufficient to configure a small 16-bit LSI-11 microcomputer system within the case, and supported an optional dual TU58 DECtape II block-addressable cartridge tape drive which could be used like a very slow disk drive. The VT180 (codenamed "Robin") added a single-board microcomputer using a Zilog Z80 to run the CP/M operating system. The VT278 (DECmate) added

335-417: A marker on graph 0 by examining register 1 to see if markers are turned on, looking in the marker buffer to see if there is a 1 at the current X location, and then examining the Y location of graph 0 to see if it is within 16 pixels of the current scan line. If all of these are true, a spot is drawn to present that portion of the marker. As this will be true for 16 vertical locations during the scanning process,

402-483: A minimum speed of 50 bit/s, but increased the maximum speed to 19,200 bit/s, double that of the VT52. 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. The major internal change

469-476: A small PDP-8 processor, allowing the terminal to run Digital's WPS-8 word processing software. VT220 The VT200 series is a family of computer terminals introduced by Digital Equipment Corporation (DEC) in November 1983. The VT220 was the basic version, a text-only version with multi-lingual capabilities. The VT240 added monochrome ReGIS vector graphics support to the base model, while

536-445: A symbol of some sort would normally be used. The system also allowed a vertical line to be drawn for every horizontal location and a horizontal one at every vertical location. These were also stored as simple on/off bits, requiring another 128 bytes of memory. These lines were used to draw axes and scale lines, or could be used for a screen-spanning crosshair cursor. A separate set of two 7-bit registers held additional information about

603-411: Is a line (0), the next that graph 0 is a histogram (1), that both graphs are on (11) and that the entire graphics system is enabled (1). The resulting pattern is equivalent to decimal 47, the / character. This mode would be enabled with the string A / . The I register was loaded using similar encoding, but the bits controlled the display of markers and the horizontal and vertical lines. As with A,

670-420: Is encountered, and the following two characters are used to move the starting X location to the center of the screen. This is followed by a second line segment being drawn in graph 1 using the J. Two markers are then added, one on each line, centered along the segments. The line segments are 16 pixels wide and the markers are always 16 high. The result are cross shapes, one in the lower left and another centered. As

737-413: Is still in graph drawing mode. One could turn graph 1 into a histogram by sending A7 , causing a vertical bar to be drawn extending down from the center of the screen. Sending ESC2 would exit graphics mode, at which point further characters are interpreted as normal text. The VT105 was broadly similar to the VT55, but added a number of additional features. One was a square format mode that reduced

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804-506: 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

871-506: The VT50 (1974), and soon upgraded to the VT52 (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

938-680: The VT55 and VT105 terminals in the mid-1970s. It was used to produce graphics output from mainframes and minicomputers . DEC used the term "waveform graphics" to refer specifically to the hardware, but it was used more generally to describe the whole system. The system was designed to use as little computer memory as possible. At any given X location it could draw two dots at given Y locations, making it suitable for producing two superimposed waveforms , line charts or histograms . Text and graphics could be mixed, and there were additional tools for drawing axes and markers. The waveform graphics system

1005-454: The shade line . This worked in conjunction with the histogram to allow the direction of the filling to be changed. On the VT55 the filling always drew down from the graph to the base of the display, on the VT105 with the shade line set, this could be set to draw up to the top of the screen, or more commonly, towards a center-point in the data. For instance, with the shade line set to the middle of

1072-545: The storage tubes used in the Tektronix 4010 terminals, or the zero memory racing-the-beam system used in the Atari 2600 . DEC chose to attack this problem through a clever use of a small buffer representing only the vertical positions on the screen. Such a system could not draw arbitrary shapes, but would allow the display of graph data. The system was based on a 512 by 236 pixel display, producing 512 vertical columns along

1139-404: The 10-bit decimal pattern 0010010010. That is then split that into upper and lower 5-bit parts, 00100 and 10010. Then append 01 binary to produce 7-bit numbers 0100100 and 0110010. Individually convert back to decimal 40 and 50, and then look up those characters in an ASCII chart, finding ( and 2. These have to be sent to the terminal least significant character first. If these were being used to set

1206-408: The 1024 number space (2 ) can be stored as a string of two characters. To ensure the characters can be transmitted over 7-bit links, the pattern 01 is placed in front of both 5-bit numbers, producing 7-bit ASCII values that are always within the printable range. This results in a somewhat complex encoding algorithm. For instance, if one wanted to encode the decimal value 102, first you convert that to

1273-502: 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 as waveform graphics which

1340-529: The A and I commands. The first data character worked as it had under the VT55, and thus provided backward compatibility. The second turned on the new features. The second character sent to the A controlled shading lines and the strip-chart feature; least significant bit, bit 0, set the shade line data sent with @ to be loaded into graph 0 or graph 1, while bits 2 and 3 turned the shade line on or off for graph 0 or 1, respectively. Turning on bit 3 allowed strip charts to be used, while bit 4 turned it on for both graphs,

1407-459: The DEClab 11/03 system. The DEClab normally sold for $ 14,000, equivalent to $ 86,494 in 2023 with a DECwriter II (LA36) hard-copy terminal for $ 15,000, equivalent to $ 86,494 in 2023, with the VT55. The system had I/O channels for up to 15 lab devices, and included libraries for FORTRAN and BASIC for reading the data and creating graphs. The fairly extensive VT55 Programmers Manual covered

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1474-541: The VT100 User Guide. The VT100 was the first of Digital's terminals to be based on an industry-standard microprocessor, the Intel 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

1541-529: The VT100 used the new Intel 8080 as its internal processor . In addition, the VT100 provided backwards compatibility for VT52-compatible software, by also supporting the older control sequences. 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 additional box-drawing character set containing various pseudographics that allowed

1608-615: The VT100 was replaced by the more powerful VT200 series terminals such as the VT220 . 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 the VT1XX-AB (Advanced Video Option) and the VT1XX-AA (20 mA Current Loop Option). The cards' capabilities and existence are described in Chapter 4 of

1675-518: 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. 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,

1742-623: The VT100s version, and connected to the terminal using a lighter and more flexible coiled cable and a telephone jack connector. The VT200s were the last DEC terminals to provide a 20mA current loop serial interface (using a 8-pin Molex -style connector), an older standard originally developed for the telegraph system but became popular on computers due to the early use of Teletype Model 33 's as ad hoc terminals. A standard 25-pin D-connector

1809-434: The X coordinate, the complete string would be H 2 ( . When used as X and Y locations for the graphs, extra digits were ignored. For instance, the 512 pixel X axis requires only 9 bits to encode, so the 10th bit was ignored. Likewise, Y locations ignored the 9th and 10th bits. Control registers always contained 7 bits, with the most significant bits always being 01. In register zero, bit 0 (least significant) turned

1876-471: The X location every time an Y coordinate was received, so a graph line could be sent as a long string of numbers for subsequent Y locations instead of having to repeatedly send the X location every time. Drawing normally started by sending a single instruction to set the initial X location, often 0 on the left, and then sending in data for the entire curve. The system also included storage for up to 512 marker s on both lines. These were always drawn centered on

1943-586: The X-axis, and 236 horizontal rows on the Y-axis. Y locations were counted up from the bottom, so the coordinate 0,0 was in the lower left, and 511, 235 in the upper right. Had this been implemented using a framebuffer with each location represented by a single bit, 512 ⨉ 236 x 1 = 120,832 bits, or 15,104 bytes, would have been required. At the time, memory cost about $ 50 per kilobyte, so the buffer alone would cost over $ 700, equivalent to $ 4,325 in 2023. Instead,

2010-409: The Y value of the line they were associated with, meaning that a simple on/off indication for X locations was all that was needed, requiring only 1024 bits, or 128 bytes, in total. The markers extended 16 pixels vertically, and could only be aligned on 16-pixel boundaries, so they were not necessarily centered across the underlying graph. Markers were used to indicate important points on the graph, where

2077-678: The case of systems like the IBM 3270 , which generally required expensive controllers for distributed applications. In contrast, "dumb terminals" or "glass teletypes" like the ADM-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 its host system over serial lines at

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2144-456: The case was a carrying handle that could also be used to angle the monitor more foward. An extendable post could do so to even greater angles, allowing the monitor to face directly forward. The LK201 keyboard supplied with the VT220 was one of the first full-length, low-profile keyboards available; it was developed at DEC's Roxbury , Massachusetts facility. It was much smaller and lighter than

2211-660: 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

2278-399: The characters were subscript 0 through 9 and the upper part of fractions 1/, 2/, 3/, 5/ and 7/. These could be combined to form, for instance, 3 ⁄ 7 . The set also included horizontal bars at each of the 8 scan lines in a normal glyph, the degree symbol, and other common examples. These used separate character codes, so graphics characters could be mixed with the normal character set on

2345-404: The display horizontally by eight character widths and extended it vertically by one line to make it more square than the original layout. This left additional room on the left for eight characters instead of a single vertical column, improving label displays. The VT105 also changed the meaning of register 0's bits slightly; bit 1 and 2 no longer turned on and off the entire graph, but the display of

2412-421: 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 in non-volatile memory within 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

2479-473: The drawing style and other settings. Although complex from the user's perspective, this system was easy to implement in hardware. A cathode ray tube produces a display by scanning the screen in a series of horizontal motions, moving down one vertical line after each horizontal scan. At any given instant during this process, the display hardware examines a few memory locations to see if anything needs to be displayed. For instance, it can determine whether to draw

2546-445: The dual strip feature. The second character on the I command had only two values, ! or space; sending ! put the terminal into square mode, while space, or nothing, left it in the VT55 compatible rectangle format. The VT50 series also included an alternate character set, graphics mode , that could be switched in and out while in text mode. These were used to provide additional glyphs useful for labeling and similar tasks. Among

2613-430: The easily readable command I 0 . Markers and lines required only one coordinate to be sent, an X or Y. In the case of a marker, the Y location was defined by the data previously set with B or J. For lines, the second coordinate spanned the screen. For instance, a vertical line could be placed at location 102 on the X axis with the string L 2 ( . Both markers and lines could be cleared by setting bit 5 of

2680-416: The entire line drawing system on or off. Bits 1 and 2 turned the individual graphs 0 or 1 on or off, and bits 3 and 4 controlled whether graphs 0 and 1 were lines or filled in to make histograms. For instance, if one wanted to have both graphs on-screen, but graph 0 would be a histogram and graph 1 would be a line, the required bit pattern would be 0101111, the leading 01 being fixed, the next bit saying graph 1

2747-432: The graph points themselves. This allowed the display to make a line, a shaded histogram, or a histogram with a brighter line on top. In comparison, on the VT55 the graph bit controlled the display of the entire dataset, not just the line itself, so turning off the graph bit would make the histogram disappear as well. Another change was to re-use the @ command, formerly the noop , to allow a new Y position to be sent in as

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2814-587: The graphics hardware, so text and graphics could not be mixed in a single stream of instructions. Graphics mode was entered by sending the string ESC 1 , and exited again with the string ESC 2 . Even the commands within the graphics mode were modal; characters were interpreted as being additional data for the previous load character (command) until another load character is seen. Ten load characters were available: X and Y locations were sent as 10-bit decimal numbers, encoded as ASCII characters, with 5 bits per character. This means that any number within

2881-445: The latter in depth. Data was sent to the terminal using an extended set of codes similar to those introduced on the VT52 . VT52 codes generally started with the ESC character (octal 33, decimal 27) and was then followed by a single letter instruction. For instance, the string of four characters ESC H ESC J would reposition the cursor in the upper left (home) and then clear

2948-601: The less-expensive $ 545 VT300 series in 1987. By that time, DEC had shipped over one million VT220s. The VT220 improved on the earlier VT100 series of terminals with a redesigned keyboard, much smaller physical packaging, and a faster microprocessor, the Intel 8051 microcontroller . The VT220 was available with CRTs that used white, green, or amber phosphors . The VT100s, like the VT50s before them, had been packaged in relatively large cases that provided room for expansion systems. The VT200s abandoned this concept, and wrapped

3015-404: The line to be drawn from the left to right like the VT55, but additional data points would push the previous data to the left. If markers or vertical axis lines were set, they too were pushed over, following the data. In dual strip mode , adding data to graph 1 caused both graphs to move over at the same time. All of these new features were controlled through optional second characters added to

3082-399: The markers are centered on 16-pixel boundaries and cannot be drawn outside the visible area, the first marker on the lower segment will appear above the line, creating an upside-down T shape rather than a cross. The last two commands, D and L, produce two horizontal lines at the bottom and center of the screen, and three vertical lines at the left, center and right. At this point the terminal

3149-521: The middle of the top row of keys. For users of the TECO editor, in which it is heavily used, this was inconvenient. 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 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

3216-400: The most significant bits were always 01, the least significant bit turned on or off horizontal lines, bit 1 the same for vertical, 2 and 3 whether or not to display markers on graph 0 or 1 respectively, and setting bit 5 would clear out all the data for the markers and lines. That meant that one could clear the display by sending the bit pattern 0110000, decimal 48, the character 0. This produces

3283-401: The much smaller 1980s-era electronics tightly around the CRT. The result was a truncated pyramidal case with the apex at the back, only slightly larger than the CRT. This made it much easier to fit the terminal on a desk. Normally the monitor sat facing upward at about a 15 degree angle. Because it was lower than head height, the result was an especially ergonomic terminal. On the rear bottom of

3350-603: 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 Dynamically Redefined Character Set (DRCS), which could be downloaded from the host computer. Data for the glyphs was sent by encoding a set of six vertical pixels into a single character code, and then sending many of these Sixels to

3417-511: 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. Waveform graphics Waveform graphics is a simple vector graphics system introduced by Digital Equipment Corporation (DEC) on

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3484-473: The same V240 base unit with VR-241 color monitor. A VT240 can be upgraded to a VT241 by replacing the monitor and the cable. The VT220 was designed to be compatible with the VT100 , but added features to make it more suitable for an international market. This was accomplished by including a number of different character sets that could be selected among using a series of ANSI commands. Glyphs were formed within

3551-519: The screen from that point down. These codes were basically modeless ; triggered by the ESC the resulting escape mode automatically exited again when the command was complete. Escape codes could be interspersed with display text anywhere in the stream of data. In contrast, the graphics system was entirely modal, with escape sequences being sent to cause the terminal to enter or exit graph drawing mode . Data sent between these two codes were interpreted by

3618-426: The screen, if a sine wave was plotted the areas above the center would be shaded downwards and the sections below center upwards, producing a filled-in waveform. Enabling a horizontal line at the same point adds a visual baseline. There were two shade lines in memory, one for each graph, but only one @ command. A bit in register 1 controlled which of the two buffers the @ data was loaded into. Another major addition

3685-404: The string of 1's produces an 8-pixel horizontal line in the lower left of the screen drawn using graph 0. The X location starts at the default location 0, and moves over one location with every following data point, which always consists of two characters. There is no need to type B in again, the string is modal and the current command remains B until another is encountered. That occurs when the H

3752-524: The terminal, rather than requiring the terminal to be set to a separate less-efficient graphics mode like the VT105. The VT131 added block mode support, 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. The VT100 form factor left significant physical space in the case for expansion, and DEC used this to produce several all-in-one stand-alone minicomputer systems. The VT103 included

3819-400: The terminal, which decoded them into the character set memory. In later models, the same sixel concept would be used to send bitmapped graphics as well. Character graphics were a common example of these downloaded sets. Prior to the VT220, if an Escape key was present, it was positioned in the upper left corner of the keyboard. The VT220 moved it to the typical location for the f11 key, in

3886-408: The third character, which would otherwise be unused. The following example produces a simple graphic: ESC1A'I?B1111111111111111H (J6666666666666666C$ 09K$ 8D+723L 0?? 8 The first two characters tell the terminal to enter graphics mode, while the next four set the two drawing mode registers to turn on both graph lines, markers on both, and enables horizontal and vertical lines. The B followed by

3953-436: The waveform graphic system used one byte of memory for each X axis location, with the byte's value representing the Y location. This required only 512 bytes for each graph, a total of 1024 bytes for the two graphs. Drawing a line required the programmer to construct a series of Y locations and send them as individual points, the terminal could not connect the dots itself. To make this easier, the terminal automatically incremented

4020-513: 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. This eliminated

4087-455: Was also provided for RS-232. Only one of the two ports could be in use at a given time. Later DEC terminals would replace both of these with their proprietary Modified Modular Jack (MMJ) connectors. Another version of the terminal, the VT240, used DEC's own DEC T-11 , a single-chip microcontroller version of the PDP-11 minicomputer . The VT241 is the color version of the VT240, consisting of

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4154-418: Was extremely successful in the market. Released at $ 1,295, 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

4221-469: Was introduced on the VT55 terminal in October 1975, an era when memory was extremely expensive. Although it was technically possible to produce a bitmap display using a framebuffer using technology of the era, the memory needed to do so at a reasonable resolution was typically beyond the price point that made it practical. All sorts of systems were used to replace computer memory with other concepts, like

4288-410: Was mostly compatible with same system in the earlier VT55 . 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. The VT125 added an implementation of the byte-efficient Remote Graphic Instruction Set ( ReGIS ), which used custom ANSI codes to send graphics commands to

4355-401: Was the concept of strip graphs , a mode that emulated paper pen plotters that moved up and down while the paper was wound under them. These were commonly used for recording scientific data, but are perhaps best known on older lie detectors . As new data points were added to one of the graphs, previous data was shifted to the left. Thus, sending a series of Y values using B or J would first cause

4422-515: Was the control protocol. Unlike the VT50/52's proprietary cursor control language, the VT100 was based on the newly emerging ANSI X3.64 standard for command codes. At the time, some computer vendors had suggested that the new standard was beyond the state of the art and could not be implemented at a reasonable price. The introduction of low-cost microprocessors and the ever-falling cost of computer memory offered greatly expanded capabilities, and

4489-489: Was used only for a short period of time before it was replaced by the more sophisticated ReGIS system, first introduced on the VT125 in 1981. ReGIS allowed the construction of arbitrary vectors and other shapes. Whereas DEC normally provided a backward compatible solution in newer terminal models, they did not choose to do this when ReGIS was introduced, and waveform graphics disappeared from later terminals. Waveform graphics

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