A monochrome monitor is a type of
computer monitor
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
The ...
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
A cash register, sometimes called a till or automated money handling system, is a mechanical or electronic device for registering and calculating transactions at a point of sale. It is usually attached to a drawer for storing cash and other ...
systems, owing to the age of many registers. Green screen was the common name for a monochrome monitor using a
green
Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combin ...
"P1"
phosphor
A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or v ...
screen; the term is often misused to refer to any block mode display terminal, regardless of color, e.g.,
IBM 3279
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971
and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the tex ...
,
3290.
Abundant in the early-to-mid-1980s, they succeeded
Teletype
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Init ...
terminals and preceded color CRTs and later
LCDs as the predominant visual output device for computers.
CRT Design
The most common technology for monochrome monitors was the
CRT, although, e.g.,
plasma display
A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be rele ...
s, were also used.
Unlike color monitors, which display text and graphics in multiple colors through the use of alternating-intensity red, green, and blue
phosphor
A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or v ...
s, monochrome monitors have only one color of phosphor (''mono'' means "one", and ''chrome'' means "color"). All text and graphics are displayed in that color. Some monitors have the ability to vary the brightness of individual
pixels
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the sm ...
, 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
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special ...
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.
An amber screen was claimed to give improved ergonomics, specifically by reducing eye strain; this claim appears to have little scientific basis.
Usage
Well-known examples of early monochrome monitors are the
VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special ...
from
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president un ...
, released in 1978, the
Apple Monitor III in 1980, and the
IBM 5151, which accompanied the
IBM PC
The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
model 5150 upon its 1981 release.
The 5151 was designed to work with the PC's
Monochrome Display Adapter (MDA) text-only
graphics card
A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer mo ...
, but the third-party
Hercules Graphics Card The Hercules Graphics Card (HGC) is a computer graphics controller made by Hercules Computer Technology, Inc. that combines IBM's text-only MDA display standard with a bitmapped graphics mode. This allows the HGC to offer both high-quality text a ...
became a popular companion to the 5151 screen because of the Hercules' comparatively high-resolution
bitmap
In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array or bitmap index.
As a noun, the term "bitmap" is very often used to refer to a particular bitmapping application: t ...
ped 720×348 pixel monochrome graphics capability, much used for business presentation graphics generated from
spreadsheet
A spreadsheet is a computer application for computation, organization, analysis and storage of data in tabular form. Spreadsheets were developed as computerized analogs of paper accounting worksheets. The program operates on data entered in ...
s like
Lotus 1-2-3. This was much higher resolution than the alternative IBM
Color Graphics Adapter
The Color Graphics Adapter (CGA), originally also called the ''Color/Graphics Adapter'' or ''IBM Color/Graphics Monitor Adapter'', introduced in 1981, was IBM's first color graphics card for the IBM PC and established a De facto standard, de fact ...
320×200 pixel, or 640×200 pixel graphic standard. It could also run most programs written for the CGA card's standard graphics modes. Monochrome monitors continued to be used, even after the introduction of higher resolution color IBM
Enhanced Graphics Adapter
The Enhanced Graphics Adapter (EGA) is an IBM PC graphics adapter and de facto computer display standard from 1984 that superseded the CGA standard introduced with the original IBM PC, and was itself superseded by the VGA standard in 1987. In ...
and
Video Graphics Array
Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the PC industry within three years. The term can n ...
standards in the late 1980s, for
dual-monitor applications.
Clarity
Pixel for pixel, monochrome monitors produce sharper text and images than color
CRT monitors. This is because a monochrome monitor is made up of a continuous coating of phosphor and the sharpness can be controlled by focusing the electron beam; whereas on a color monitor, each pixel is made up of three phosphor dots (one red, one blue, one green) separated by a mask. Monochrome monitors were used in almost all
dumb terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal a ...
s and were widely used in text-based applications such as computerized cash registers and
point of sale
The point of sale (POS) or point of purchase (POP) is the time and place at which a retail transaction is completed. At the point of sale, the merchant calculates the amount owed by the customer, indicates that amount, may prepare an invoice f ...
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
scrolled down the screen or when a screenful of information was quickly replaced with another as in
word processing page up/down operations. Other green screens avoided the heavy afterglow-effects, but at the cost of much more
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the ...
ated character images. The 5151, amongst others, had brightness and contrast controls to allow the user to set their own compromise.
The ghosting effects of the now-obsolete green screens have become an eye-catching visual shorthand for computer-generated text, frequently in "futuristic" settings. The opening titles of the first ''
Ghost in the Shell'' film and the
Matrix source code of the
Matrix trilogy science fiction film
Science fiction (or sci-fi) is a film genre that uses speculative, fictional science-based depictions of phenomena that are not fully accepted by mainstream science, such as extraterrestrial lifeforms, spacecraft, robots, cyborgs, interstel ...
s prominently feature computer displays with ghosting green text. Green text is also featured in
the Swan's computer in ''
Lost
Lost may refer to getting lost, or to:
Geography
* Lost, Aberdeenshire, a hamlet in Scotland
*Lake Okeechobee Scenic Trail, or LOST, a hiking and cycling trail in Florida, US
History
*Abbreviation of lost work, any work which is known to have bee ...
'' series.
Phosphor limitations
Monochrome monitors are particularly susceptible to
screen burn (hence the advent, and name, of the
screensaver
A screensaver (or screen saver) is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a designated time. The original purpose of screensavers was to prevent phosphor ...
), because the phosphors used are of very high intensity.
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 has a certain place in
pop culture
Pop or POP may refer to:
Arts, entertainment, and media Music
* Pop music, a musical genre Artists
* POP, a Japanese idol group now known as Gang Parade
* Pop!, a UK pop group
* Pop! featuring Angie Hart, an Australian band
Albums
* ''Pop'' ...
, as evidenced in movies such as ''
The Matrix
''The Matrix'' is a 1999 science fiction action film written and directed by the Wachowskis. It is the first installment in ''The Matrix'' film series, starring Keanu Reeves, Laurence Fishburne, Carrie-Anne Moss, Hugo Weaving, and Joe Pantolia ...
'' through its
digital rain effect.
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.
See also
*
IBM 3270
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971
and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the te ...
*
IBM 5250
*
IBM 5151
*
Apple Monitor III
References
{{reflist
Display devices
Legacy hardware
Obsolete technologies
User interfaces