visual display unit

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visual display unit

Computing a device with a screen that displays characters or graphics representing data in a computer memory. It usually has a keyboard or light pen for the input of information or inquiries
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

visual display unit

[′vizh·ə·wəl di′splā ‚yü·nət]
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Visual Display Unit

(VDU, or "video terminal", "video display terminal", VDT, "display terminal") A device incorporating a cathode ray tube (CRT) display, a keyboard and a serial port. A VDU usually also includes its own display electronics which store the received data and convert it into electrical waveforms to drive the CRT.

VDUs fall into two categories: dumb terminals and intelligent terminals (sometimes called "programmable terminals").

Early VDUs could only display characters in a single preset font, and these were confined to being layed out in a rectangular grid, reproducing the functionality of the paper-based teletypes they were designed to replace.

Later models added graphics facilities but were still driven via serial communications, typically with several VDUs attached to a single multi-user computer. This contrasts with the much faster single bitmap displays integrated into most modern single-user personal computers and workstations.

The term "Display Screen Equipment" (DSE) is used almost exclusively in connection with the health and safety issues concerning VDUs.

Working with VDUs - UK Heath and Safety Executive.
This article is provided by FOLDOC - Free Online Dictionary of Computing (
References in periodicals archive ?
Japanese scientists have investigated the possibility that visual disorders associated with VDU use are caused by the effect of stress on the central nervous system.
A study carried out in Israel tested accommodation and convergence on VDU workers.
A survey of optometrists conducted by the American Optometric Association (AOA), who have labelled this condition "computer vision syndrome" (CVS), (18) indicated that 10 million primary eye care examinations are provided annually in the USA primarily because of visual problems associated with VDU use.
The HSE and the College of Optometrists (19) accept this last point-"unnoticed eyesight anomalies, that have caused no problems previously, can become very troublesome when a person becomes a VDU user." (20, 21) Indeed, research has shown that minor, and otherwise unnoticed, refractive errors or astigmatism could cause pronounced discomfort after as little as hall an hour in front of a VDU and that properly fitted lenses could noticeably increase comfort.
Most studies indicate that visual symptoms occur in >50% of VDU workers, while one study in particular showed that 22% of VDU workers have musculoskeletal disorders.
Many individuals who work at a VDU report a high level of job-related complaints and symptoms, including ocular discomfort, muscular strain and stress.
Aspects of the design of the VDU such as screen resolution and contrast, image refresh rates and flicker, and screen glare, as well as working distances and angles, may all contribute to worker symptoms.
Get the VDU user to adjust seat height and the back of their chair
Merle Blok labelled the worst posture for VDU use "the vulture" (Figure 2).
With presbyopic patients, optometrists will also check residual accommodation and the appropriate near refraction; intermediate focus for VDU distance will also be conducted if indicated.
This makes a VDU task more difficult, increasing stress on the worker; which produces a repeating cycle that leads to the collapse of visual function.