A monitor or display (sometimes called a visual display unit) is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD), while older monitors use a cathode ray tube (CRT).
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The size of a display is usually given as the distance between two opposite screen corners. One problem with this method is that it does not distinguish between the aspect ratios of monitors with identical diagonal sizes, despite the fact that the area of a given diagonal span decreases as it becomes less square. For example, a 4:3 21-inch (53.3 cm) monitor has an area of about 211 sq in (1,361 cm2), while a 16:9 21-inch widescreen has about 188 sq in (1,213 cm2).
This method of measurement is from the first types of CRT television, when round picture tubes were in common use. Being circular, 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 continued even when cathode ray tubes were manufactured as rounded rectangles.
Another problematic practice was the direct measurement of a monitor's imaging element as its quoted size in publicity and advertising materials. Especially on CRT displays, a substantial portion of the imaging element is concealed behind the case's bezel or shroud in order to hide areas outside the monitor's safe area due to overscan. Seen as deceptive, widespread consumer objection and lawsuits eventually forced most manufacturers to instead measure viewable size.
Contents[hide].
The size of a display is usually given as the distance between two opposite screen corners. One problem with this method is that it does not distinguish between the aspect ratios of monitors with identical diagonal sizes, despite the fact that the area of a given diagonal span decreases as it becomes less square. For example, a 4:3 21-inch (53.3 cm) monitor has an area of about 211 sq in (1,361 cm2), while a 16:9 21-inch widescreen has about 188 sq in (1,213 cm2).
This method of measurement is from the first types of CRT television, when round picture tubes were in common use. Being circular, 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 continued even when cathode ray tubes were manufactured as rounded rectangles.
Another problematic practice was the direct measurement of a monitor's imaging element as its quoted size in publicity and advertising materials. Especially on CRT displays, a substantial portion of the imaging element is concealed behind the case's bezel or shroud in order to hide areas outside the monitor's safe area due to overscan. Seen as deceptive, widespread consumer objection and lawsuits eventually forced most manufacturers to instead measure viewable size.
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