Editing VT52 (section)

== Versions ==

=== VT50 ===
The VT50 was the first terminal Digital produced in this cabinet. It provided only 12 lines of text with blank lines between them to use the entire vertical area of the display. Like its predecessor, the [[VT05]], the VT50 did not support lowercase letters.{{sfn|DECscope|1975|p=11}} Computer users of that era seldom needed lowercase text.

=== VT50H ===
The VT50H added a separate "auxilary keyboard" on the right side of the original keyboard. This was arranged in the fashion of a [[numeric keypad]] with additional [[control key]]s above the numbers. Four of these were [[cursor key]]s which sent {{key|ESC}}{{key|A}} through {{key|D}} for up, down, left and right, respectively. Another three of the keys were unlabeled and could be programmed to return any two-character code, and would default to {{key|ESC}}{{key|P}} through {{key|R}}.{{sfn|DECscope|1975|p=14}}

=== VT52 ===
The VT50 was soon replaced by the greatly upgraded VT52. The VT52 had considerably larger buffers, giving it the capacity to store not only a full 24 lines of text that better utilized the screen space, but also the text off the top and bottom of the screen. This allowed the terminal to scroll backwards a limited amount without having to ask the host to re-send data. Another significant upgrade was that the VT52 included lowercase text support.{{sfn|DECscope|1975|p=11}} Many new commands and features were added:{{sfn|DECscope|1975|pp=12-30}}

* Support for the {{key|:}}, {{key|~}} and {{key|&#125;}} characters, when the shift key was used with {{key|;}}, {{key|`}} or {{key|&#123;}}, respectively.
* Typing on the numeric keypad could now be distinguished from the main keyboard by turning on Alternate-Keypad Mode. This returned multi-character codes, {{key|ESC}}{{key|?}}{{key|n}} through {{key|y}}.
* New cursor control codes to support host-directed full-screen editing and a [[WYSIWYG]] display.
* A "graphics character set" which included several less-common characters as well as the ability to print some fractions in-line, like {{frac|3|7}}.

One notable feature was the introduction of a separate function keypad with the "[[Gold key (DEC)|Gold Key]]", which was used for editing programs like [[WPS-8]], KED, and [[EDT (Digital)|EDT]]. Pressing the Gold Key and then typing one of the keys on the keyboard sent a command sequence back to the host computer.

=== VT55 ===
The '''VT55''' incorporated an add-on graphics system that was capable of displaying two mathematical functions or [[histogram]]s. This was invoked by sending a command string that sent the terminal into ''graphics mode'', with further data being sent to a separate buffer and CPU. Both systems mixed their data during the display, allowing the user to mix graphics and text on a single screen, as opposed to systems like the [[Tektronix 4010]] or [[plotter]]s that had to slowly draw text using graphics commands. This system became known as [[waveform graphics]], and would re-appear on the later VT105.

=== Block mode versions ===
The '''VT61''' and '''VT62''' were [[Block-oriented terminal|block-mode terminals]]. The VT62 was to be used in conjunction with TRAX, a transaction processing operating system on high-end [[PDP-11]]s. They used the same cabinet but had a more complete custom processor. Application-specific behavior was coded in separate [[Programmable read-only memory|PROM]] memory, using a separate instruction code that the processor interpreted. This unpublished language was to be used to easily develop additional models specific to single Digital marketing organizations. These terminals synthesized a "tock" sound on a speaker for feedback when a key was pressed instead of the relay. Though the keyboards were identical, VT6x users admired the superior "feel".

=== VT78 ===
The relatively large expansion area of the VT50 case, combined with rapidly shrinking electronics in the late 1970s, allowed DEC to produce single-box, stand-alone [[minicomputer]]/terminals similar to a contemporary [[microcomputer]]. The [[VT78]] added a single-chip [[PDP-8]] processor to the VT52, ran a variant of Digital's [[OS/8]] operating system, and usually [[WPS-8]], Digital's [[word processing]] system.