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Colloquially, a 'computer display', 'computer monitor', or 'computer screen' (and historically, computer terminal monitor) is a computer peripheral device which is capable of showing video output to the user of a computer. In the technical sense, there are many types of computer display devices, and the proper terminology is computer video display, or shorter computer monitor. It is part of the general class of computer output devices (display devices, thus are a sub-class) which also includes computer peripherals like: 'factory pattern-cutting equipment', 'variable power (controled) laser systems', observatory telescopes, computer printers, 'machine tools', 'audio headsets' (There is a computer in that MP3 player), 'microwave ovens and modern stoves', 'automobile dashboards' and 'automobile engines', various 'amusement park rides' and etcetera; all devices a computer can and do directly control and command in today's world.
In the more common day to day world, computers control a 'video card' which formats the output appropriate to a compatible computer monitor which displays alphanumeric text characters that humans can read and interpret, and in this later age, symbols such as icons, and graphics such as images generated by a computer and processed through a high-end video card known technically as a computer graphics card.
Monitors generally conform to one or more display standards. The genesis of the term 'monitor' dates back to the early days of computing prior to computer time sharing where 'computer systems operators' would monitor the central computer system, and persons desiring a computing task would submit a request with the proper documentation, data (typically computer punch cards, and authorization which would be scheduled into a particular 'session' called a 'batch' (this is a discription, as a result of that, of what is called 'batch processing') and processed by the computer department when the machine resources and man-power were available. The particular application program of the day of Mainframe and Minicomputer's would be stored on Magnetic Tape, Computer paper tapes, or on computer punch cards and 'loaded' by the 'sys-op' (system operator).
To some inexperienced technical users the name "display" suits better than the word "monitor", as the latter term can also ambiguously refer to technical specialty terms (a "machine-level debugger" or to a "thread synchronization mechanism").
Some people also refer to computer displays as "heads", especially when talking about multiple displays connected to a single physical computer, again a practice more common in computer technical practices rather than common use. Once an essential component of a computer terminal, computer displays have long since become standardized peripherals in their own right. There are many types of monitors.
Technologies
As with television, several different hardware technologies exist for displaying computer-generated output:
- Cathode ray tube (CRT)
- Liquid crystal display (LCD). (LCD-based monitors can receive television and computer protocols (SVGA, PAL, SECAM; NTSC))
- Plasma display
- Surface-conduction electron-emitter display (SED)
- Video projector
- Organic light-emitting diode (OLED) display.
A modern CRT display has considerable flexibility: it can usually handle a range of resolutions from 320 by 200 pixels (320x200) up to 2048 by 1536 pixels (2048x1536) or 2304 by 1440 pixels (2304x1440), with unlimited colours and a variety of refresh rates.
As of 2005, the highest known maximum native resolution for any type of monitor is 3840 by 2400 pixels (3840x2400) on an LCD screen.
Dot pitch measures the sharpness of a display. In general, the lower the dot pitch, (e.g. 0.24), the sharper the picture will appear.
Early CRT-based VDUs (Visual Display Units) without graphics capabilities gained the label "glass teletypes", because of the functional similarity to their electromechanical predecessors.
Black-and-white displays can only display one colour: either as on or off. Monochrome displays can show only levels of a single colour. In both cases the display usually uses green, orange (amber) or gray (white).
Colour monitors may show either digital colour (turning each of the red, green and blue signals either on or off, giving eight possible colours: black, white, red, green, blue, cyan, magenta and yellow - sometimes with an extra "brightness" signal producing a total of up to 16 colours) or analog colour (red, green and blue signals vary continuously, allowing the display of any combination). Early digital monitors are sometimes known as TTLs because the voltages on the red, green and blue inputs are compatible with TTL logic chips. Later digital monitors support LVDS, or TMDS protocols.
Most modern computer displays can show thousands or millions of different colours in the RGB colour space by combining red, green, and blue dots in varying intensities.
With exceptions of DLP, most display technologies (especially LCD) have an inherent misregistration of the colour planes, that is, the centers of the red, green, and blue dots do not line up perfectly. Subpixel rendering depends on this misalignment; technologies making use of this include the Apple II from 1976 [1], and more recently Microsoft (ClearType, 1998) and XFree86 (X Rendering Extension).
Moving texts can appear in italics, even when the display resolution is too low to show static italics: a fractional time delay causes an apparent corresponding shift of a fraction of a pixel.
Note the sometimes disputed issue of screen emissions. Most computer monitors have analog signal relay, but some (mostly LCD screens) start supporting digital input signals. It is a common misconception that all computer monitors are digital. For several years, Televisions, composite monitors and computer displays have had significant distinction, however it has blurred as newer TVs have become versatile to accommodate these purposes.
History
A trend of miniaturization within computer displays has seen a general move away from the older, bulky CRT devices in the general direction of flat screens as found in modern laptops.
Major manufacturers
- Apple Computer
- BenQ
- Dell, Inc.
- Eizo
- Iiyama Corporation
- LaCie
- LG Electronics
- NEC/Mitsubishi
- Philips
- Samsung
- Sony
- ViewSonic
Performance Measurements
The relevant performance measurements of a monitor are:
- Luminance
- Size
- Dot pitch
- Color temperature
- Contrast ratio
- Interface (DVI or VGA, commonly)
- H-sync rate
- V-sync rate
- Response time
- Refresh rate
Source: http://www.wikipedia.org
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