Visual display unit
A 19" LG flat-panel LCD monitor.
A visual display unit, often called simply
a monitor or display, is a piece of electrical
equipment which displays images generated
from the video output of devices such as com-
puters, without producing a permanent re-
cord. Most newer monitors typically consist
of a [TFT-LCD](thin film transistor liquid
crystal display) with older monitors based
around a cathode ray tube (CRT). Almost all
of the mainstream new monitors being sold
on market now are LCD. The monitor com-
prises the display device, simple circuitry to
generate and format a picture from video
sent by the signals source, and usually an en-
closure. Within the signal source, either as
an integral section or a modular component,
there is a display adapter to generate video
in a format compatible with the monitor.
Screen size
Diagonal size
The size of a display is typically given as the
distance between
two opposite
screen
corners. One problem with this method is
that it does not distinguish between the as-
pect ratios of monitors with identical diagon-
al sizes, in spite of the fact that a shape of a
given diagonal span’s area decreases as it be-
comes less square. For example, a 4:3 21"
monitor has an area of ~211 square inches,
For any rectangular section on a round tube,
the diagonal measurement is also the diamet-
er of the tube
while a 16:9 21" widescreen has an area of
only ~188 square inches.
This method of measurement is from the
first types of CRT television, when round pic-
ture tubes were in common use. Being circu-
lar, they only needed to use their diameter to
describe their tube size. When round tubes
were used to display rectangular images, the
diagonal measurement was equivalent to the
round tube’s diameter. This method contin-
ued even when CRT tubes were manufac-
tured as rounded rectangles.
Another historically problematic practice
is the direct measurement of a monitor’s ima-
ging element as its quoted size in publicity
and advertising materials. Especially on CRT
displays, a sub