Difference between revisions of "Video terminal"
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| − | A '''video terminal''' was a [[terminal]] on which the characters being output were 'painted' on a [[cathode ray tube|CRT]] via a purely [[electronic]] process. It was thus roughly the same functionality as the earlier [[printing terminal]]s, such as [[Teletype]]s, but instead of the output being printed on paper by a mechanical system, it was displayed on the screen. Like the earlier printing terminals, they were used to allow a [[user]] to do [[input/output]] to a computer; they usually communicated with the computer via [[asynchronous serial line]]. | + | A '''video terminal''' (sometimes called '''video display terminal''', or '''VDT'' for short) was a [[terminal]] on which the characters being output were 'painted' on a [[cathode ray tube|CRT]] via a purely [[electronic]] process. It was thus roughly the same functionality as the earlier [[printing terminal]]s, such as [[Teletype]]s, but instead of the output being printed on paper by a mechanical system, it was displayed on the screen. Like the earlier printing terminals, they were used to allow a [[user]] to do [[input/output]] to a computer; they usually communicated with the computer via [[asynchronous serial line]]. |
The original chief advantage was speed, since the all-electronic mechanism could run at much higher speeds; the disadvantage was that only a limited amount of information could be displayed at one time. (This was particularly true of early ones, which could only display very limited amounts of text - some as small as 12 lines of 40 characters). | The original chief advantage was speed, since the all-electronic mechanism could run at much higher speeds; the disadvantage was that only a limited amount of information could be displayed at one time. (This was particularly true of early ones, which could only display very limited amounts of text - some as small as 12 lines of 40 characters). | ||
Revision as of 17:20, 26 February 2023
A video terminal' (sometimes called video display terminal, or VDT for short) was a terminal on which the characters being output were 'painted' on a CRT via a purely electronic process. It was thus roughly the same functionality as the earlier printing terminals, such as Teletypes, but instead of the output being printed on paper by a mechanical system, it was displayed on the screen. Like the earlier printing terminals, they were used to allow a user to do input/output to a computer; they usually communicated with the computer via asynchronous serial line.
The original chief advantage was speed, since the all-electronic mechanism could run at much higher speeds; the disadvantage was that only a limited amount of information could be displayed at one time. (This was particularly true of early ones, which could only display very limited amounts of text - some as small as 12 lines of 40 characters).
Very early model provided only the same motion controls as their printing predecessors - line feed, carriage return, etc. However, the ability to move the cursor to specific screen locations was soon added, which made possible a predecessor of WYSIWYG, to wit, screen editors such as EMACS.
A few had the capability to do graphics, such as lines, points, etc.
Once semiconductor RAM prices fell low enough, they were replaced with bit-mapped displays, although the latter were directly connected to the computer's main bus, usually on a personal computer.
See also
External links
- Meet the Family - a brief history of DEC VDT's
