Monochrome monitor

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An IBM computer with a green monochrome monitor
Early Nixdorf computer with an amber monitor

A monochrome monitor is a type of computer monitor in which computer text and images are displayed in varying tones of only one color, as opposed to a color monitor that can display text and images in multiple colors. They were very common in the early days of computing, from the 1960s through the 1980s, before color monitors became widely commercially available. They are still widely used in applications such as computerized cash register systems, owing to the age of many registers. Green screen was the common name for a monochrome monitor using a green "P1" phosphor screen;[1] the term is often misused to refer to any block mode display terminal, regardless of color, e.g., IBM 3279, 3290.

Abundant in the early-to-mid-1980s, they succeeded Teletype terminals and preceded color CRTs and later LCDs as the predominant visual output device for computers.

CRT Design

An open Schneider MM12 from 1988. It uses a GoldStar Type 310KGLA amber tube.

The most common technology for monochrome monitors was the CRT, although, e.g., plasma displays, were also used. Unlike color monitors, which display text and graphics in multiple colors through the use of alternating-intensity red, green, and blue

pixels
, thereby creating the illusion of depth and color, exactly like a black-and-white television.

Typically, only a limited set of brightness levels was provided to save

display memory which was very expensive in the '70s and '80s. Either normal/bright or normal/dim (1 bit) per character as in the VT100 or black, dark gray, light gray, white (2bit) per pixel like the NeXT MegaPixel Display
.

Monochrome monitors are commonly available in three colors: if the P1 phosphor is used, the screen is green monochrome. If the P3 phosphor is used, the screen is amber monochrome. If the P4 phosphor is used, the screen is white monochrome (known as "page white"); this is the same phosphor as used in early television sets.[2] An amber screen was claimed to give improved ergonomics, specifically by reducing eye strain; this claim appears to have little scientific basis.[3]

Usage

Well-known examples of early monochrome monitors are the

model 5150
upon its 1981 release.

The 5151 was designed to work with the PC's

dual-monitor
applications.

Clarity

Pixel for pixel, monochrome

dumb terminals and were widely used in text-based applications such as computerized cash registers and point of sale
systems because of their superior sharpness and enhanced readability.

Some green screen displays were furnished with a particularly full/intense phosphor coating, making the characters very clear and sharply defined (thus easy to read) but generating an afterglow-effect (sometimes called a "ghost image") when the text

word processing page up/down operations. Other green screens avoided the heavy afterglow-effects, but at the cost of much more pixelated
character images. The 5151, amongst others, had brightness and contrast controls to allow the user to set their own compromise.

Phosphor limitations

Monochrome monitors are particularly susceptible to

screen burn (hence the advent, and name, of the screensaver), because the phosphors used are of very high intensity.[citation needed
]

Another effect of the high-intensity

phosphors
is an effect known as "ghosting", wherein a dim afterglow of the screen's contents is briefly visible after the screen has been blanked.

This ghosting effect is deliberate on some monitors, known as "long persistence" monitors. These use the relatively long decay period of the phosphor glow to reduce flickering and eye strain.

In popular culture

The colour scheme, grid layout of characters, and ghosting effects of the now-obsolete monochrome CRT screens have become an eye-catching visual shorthand for computer-generated text, frequently in "futuristic" settings. The opening titles of the first

Matrix trilogy science fiction films
prominently feature computer displays with ghosting green text.

A similar grid of amber text is used in the science fiction TV show Travelers.

A free application for Linux terminal software called "Cool Retro Term" is available to accurately emulate old CRT Monochrome terminals for nostalgia or

Xscreensaver hack called phosphor which emulates a long-persistence green screen and can be used as a terminal.[5]

See also

References

  1. ^ "Cathode Ray Tube Phosphors" (PDF).
  2. ^ "Display Terminals: Market Overview" (PDF).
  3. ISBN 978-0-85066-350-1
  4. ^ https://itsfoss.com/cool-retro-term/
  5. ^ https://www.mankier.com/6/phosphor
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