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NETWORK BASICS

Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other.  


Network application
A Network application is any application running on one host and provides a communication to another application running on a different host, the application may use an existing application layer protocols such as: HTTP(e.g. the Browser and web server), SMTP(e.g. the email-client). And may be the application does not use any existing protocols and depends on the socket programming to communicate to another application. So the web application is a type of the network applications. 
There are lots of advantages from build up a network, but the th…

DISPLAY UNIT

DISPLAY UNIT

The primary method of getting information out of a computer is to use a computer video display unit (VDU).  Display systems convert computer signals into text and pictures and display them on a TV-like screen. As a matter of fact, the first personal computers used television screens because it was simpler to use an existing display technology rather than to develop a new one. Various types of computer displays are in use today, including the TV. Most all of them, projection systems as well, use the same legacy cathode  ray tube (CRT)  technology found in conventional television sets or the liquid crystal display (LCD)  technology  found on nearly all laptop, notebook, and palmtop computers. In fact, it is rare to see a desktop monitor based on CRT technology sold with a computer today.  Generally only high-end specialized units (used for enhanced clarity and video performance) are CRT-based. 

Understanding Display Types and Settings

Most display systems work the same way. First, the computer sends a signal to a device called the video adapter— an expansion board installed in an expansion bus slot or the equivalent circuitry integrated into the motherboard—telling it to display a particular graphic or character. The adapter then renders the character for the display—that is, it converts the single instruction into several instructions that tell the display device how to draw the graphic—and sends the instructions to the display device, based on the  Connection technology between the two. The primary differences after that are in the type of video adapter you are using (digital or analog) and the type of display (CRT, LCD, projector, etc.).  

Video Display Types

To truly understand the video display arena, you must be introduced to a few terms and concepts that you may not be familiar with. The legacy digital transistor-transistor logic (TTL) and the analog technologies that began with video graphics array (VGA) were once the two broad categories of video technologies. These categories have nothing to do with the makeup of the VDU but instead how the graphics adapter communicates with the VDU.  

Let’s explore the different VDU types:

  •  CRT 
  • Liquid crystal display
  • LED displays
  • Plasma
  • OLED
  • Projection  systems 


CRT Display

In a CRT, a device called an electron gun shoots a beam of electrons toward the back side of the monitor screen color CRTs often use three guns, one each for red, green, and blue image components. The back of the screen is coated with special chemical dots called phosphors (often zinc sulfide combined with other elements for color variation, but no phosphorus, ironically) that glow when electrons strike them. 

The beam of electrons scans across the monitor from left to right, as you face it, and top to bottom in a raster pattern to create the image. A special metallic screen called a shadow mask (in most implementations) has holes spaced and angled in an extremely precise manner.  For color CRTs that employ shadow masks, a trio of dot phosphors is often grouped in a triangle for each hardware picture element. The separate electron beams that control red, green, and blue strike only their own phosphors at the correct angle to cause them to glow. The glow of the phosphors decays very quickly, requiring the electron beam’s regular return to each phosphor to sustain the glow. The more dot phosphors that are placed in a given area, the better the image quality at higher resolutions. There are two ways to measure a CRT monitor’s image quality: dot pitch and resolution. Dot pitch is a physical characteristic of the monitor hardware, but resolution is configurable through software. 
  • Dot pitch Dot pitch is the measurement between the same spot in two vertically adjacent dot trios. In other words, it’s the height of the trio added to the distance between the closest extremes of it and the next trio above or below it. Expressed in millimeters or dots per inch, the dot pitch tells how “sharp” the picture can be. The lower the measurement in millimeters or the higher the number of dots per inch, the closer together the phosphors are, and as a result, the sharper the image can be. An average dot pitch is 0.28mm to 0.32mm. Anything closer than 0.28mm is considered exceptional. Dot pitch in the flat-panel arena translates to the display’s native resolution, discussed later in this chapter.  Essentially, software-pixel placement is limited to the hardware’s transistor placement, leading to one optimal resolution for each LCD. The transistors that make up the hardware’s picture elements are discussed later in the section “Liquid Crystal Displays.” 
  • Resolution Resolution is defined by how many software picture elements (pixels) are used to draw the screen. An advantage of higher resolutions is that more information can be dis- played in the same screen area. A disadvantage is that the same objects and text displayed at a higher resolution appear smaller and might be harder to see. Up to a point, the added crisp- ness of higher resolutions displayed on high-quality monitors compensates for the negative aspects. The resolution is described in terms of the visible image’s dimensions, which indicate how many rows and columns of pixels are used to draw the screen. For example, a resolution of 1024n768 means 1024 pixels across (columns) and 768 pixels down (rows) were used to draw the pixel matrix.  The video technology in this example would use 1024n768 = 786,432 pixels to draw the screen. Resolution is a software setting that is common among CRTs, LCDs, and projection systems as well as other display devices.  
  • Pixel The pixel (a word invented from "picture element") is the basic unit of programmable color on a computer display or in a computer image. Think of it as a logical - rather than a physical - unit. The physical size of a pixel depends on how you've set the resolution for the display screen. If you've set the display to its maximum resolution, the physical size of a pixel will equal the physical size of the dot pitch (let's just call it the dot size) of the display.  

If however, you've set the resolution to something less than the maximum resolution, a pixel will be larger than the physical size of the screen's dot (that is, a pixel will use more than one dot). The specific color that a pixel describes is some blend of three components of the color spectrum - RGB. Up to three bytes of data are allocated for specifying a pixel's color, one byte for each major color component. A true color or 24-bit color system uses all three bytes. However, many color display systems use only one byte (limiting the display to 256 different colors). 


Liquid Crystal Displays

Portable computers were originally designed to be compact versions of their bigger desk- top cousins. They crammed all the components of the big desktop computers into a small, suitcase-like box called (laughably) a portable computer. No matter  what the designers did to reduce the size of the computer, the display remained  as large as the desktop  version’s—that is, until an inventor  found that when he passed an electric current  through a semi-crystalline liquid, the crystals aligned themselves with the current.  It was found that by combining transistors with these liquid crystals, patterns could be formed.  These patterns could be combined to represent numbers or letters. The first application of these liquid crystal displays was the LCD watch.  It was rather bulky, but it was cool. As LCD elements got smaller, the detail of the patterns became greater, until one day some- one thought to make a computer screen out of several of these elements. This screen was very light compared to computer monitors of the day, and it consumed relatively little power. It could easily be added to a portable computer to reduce the weight by as much as 30 pounds. As the components got smaller, so did the computer, and the laptop computer was born. LCDs are not just limited to laptops; desktop versions of LCD displays and their offshoots are practically all that are seen today. Additionally, the home television market has been enjoying the LCD as a competitor of plasma for years. LCDs used with desktop computer systems use the same technology as their laptop counterparts but potentially on a much larger scale. These external LCDs are available in either analog or digital interfaces.  The analog interface is exactly the same as the VGA interface that was used for analog CRT monitors. Internal digital signals from the computer are rendered and output as analog signals by the video card and are then sent along the same 15-pin connector and associated cable as was used with analog CRT monitors. Digital LCDs with a digital interface, on the other hand, require no analog modulation by the graphics adapter. They require the video card to support digital output using a different interface, such as DVI, for instance.  The advantage is that because the video signal never changes from digital to analog, there is less chance of interference and no conversion-related quality loss. Digital displays are generally sharper than their analog counterparts.  

Two major types of LCD displays have been implemented over the years: active-matrix screens and passive-matrix screens. Another type, dual scan, is a passive-matrix variant. The main differences lie in the quality of the image. However, when used with computers, each type uses lighting behind the LCD panel (back-lighting) to make the screen easier to view. Conventional LCD panels have one or more fluorescent bulbs as back-lights. See the section “LED Displays” for details on a better type of back-light. The following discussions highlight the main differences among the pixel-addressing variants. 
Active matrix An active-matrix screen is made up of several independent LCD pixels. A transistor at each pixel location, when switched among various levels, activates two opposing electrodes that align the pixel’s crystals and alter the passage of light at that location to produce hundreds or thousands of shades. The front electrode, at least, must be clear. This type of display is very crisp and easy to look at through nearly all oblique angles, and it does not require constant refreshing to maintain an image because transistors conduct  current  in only one direction  and the pixel acts like a capacitor by holding its charge until it is refreshed with new information. Higher refresh rates are not for prevention of pixel discharge, as in the case of CRTs, plasma displays, and passive-matrix LCDs. Higher rates only result in better video  quality, not static-image quality. The major disadvantage of an active-matrix screen is that it requires larger amounts of power to operate all the transistors, one for each gray-scale pixel or each red, green, and blue sub-pixel.  Even with the back-light turned off, the screen can still consume battery power at an alarming rate, even more so when conventional fluorescent back-lights are employed.  The vast majority of LCDs manufactured today are based on active-matrix technology. 
Passive matrix  A passive-matrix display does not have a dedicated transistor for each pixel or sub-pixel but instead a matrix of conductive traces. In simplified terms for a single pixel, when the display is instructed to change the crystalline alignment of a particular pixel, it sends a signal across the x- and y coordinate traces that intersect at that pixel, thus turning it on. More realistically, circuits controlling the rows fire in series to refresh or newly activate pixels on each row in succession. The circuits controlling the columns are synchronized to fire when that row’s transistor is active and only for the pixels that should be affected on that row. Once a pixel’s charge is gone, the pixel begins to return to normal, or decay, requiring a refresh to make it appear static. Angles of visibility and response times (the time to change a pixel) suffer greatly with passive-matrix LCDs. Because neighboring pixels can be affected through a of “cross-talk,” passive-matrix displays can look a bit “muddy.” 

LED Displays

A source of confusion for users and industry professionals alike, LED displays are merely LCD panels with light emitting diodes (LEDs) as light sources instead of the fluorescent bulbs used by conventional LCD monitors. No doubt, the new technology would not be nearly as marketable if they were referred to merely as LCDs. The general consumer would not rush to purchase a new display that goes by the same name as their current display. Nevertheless, calling these monitors LED displays is analogous to calling the conventional LCD monitors fluorescent displays; it’s simply the back-light source, not the display technology. 

Because there are many individually controlled LEDs in an LED display, sometimes as many as there are transistors in the LCD panel, the image can be intelligently back-lit to enhance the quality of the picture. Additionally, there is no need for laptops with LED displays to convert the DC power coming into the laptop to the AC needed to power traditional fluorescent back-lights because LEDs operate on DC power like the rest of the laptop. As a result, these systems have no inverter board, which are the DC-to-AC conversion devices present in traditionally back-lit laptop displays. 

Plasma Displays

The word plasma refers to a cloud of ionized (charged) particles—atoms and molecules with electrons in an unstable state. This electrical imbalance is used to create light from the changes in energy levels as they achieve balance.  Plasma display panels (PDPs) create just such a cloud from an inert gas, such as neon, by placing electrodes in front of and behind sealed chambers full of the gas and vaporized mercury.  This technology of running a current through an inert gas to ionize it is shared with neon signs and fluorescent bulbs. Because of the pressurized  nature  of the gas in the chambers,  PDPs are not optimal  for high-altitude use, leading to CRTs and LCDs being more popular for high-altitude applications, such as aboard aircraft,  where PDPs can be heard to buzz the way fluorescent bulbs sometimes do. Because of the temporary emission of light that this process produces, plasma displays have more in common with CRTs than they do with LCDs. In fact, as with CRTs, phosphors are responsible for the creation of light in the shade of the three primary colors, red, green, and blue. Because the pixels produce their own light, no back-light is required with plasma displays, also a feature shared with CRTs. The phosphor chemicals in CRTs and PDPs can be “used up” over time, reducing the overall image quality.  The heat generated by CRTs and PDPs can lead to a loss of phosphorescence in the phosphor chemicals, which results in images burning into the screen. Advancements in the chemistry of plasma phosphors have reduced this tendency in recent years. 

The refresh rate for plasma displays has always been in the 600Hz range so that the decay of the glow of the cells within each pixel (sub-pixel) is not perceptible until such time as the image calls for that cell to turn off as well as to ensure fluid video motion.  Note that this rate is approximately 10 times that which is necessary to avoid the human eye’s perception of the glow’s decay. The result is a display that produces the state of the art in video motion fluidity. Higher refresh rates in LCDs lead to an unwanted artificial or no cinematic quality to video known as the “soap-opera effect.” PDPs do not suffer from this effect. PDPs can also produce  deeper black colors than fluorescent-back-lit LCD panels because the back-light  cannot  be completely blocked by the liquid crystal, thus producing hues that are grayer than black. LCDs back-lit with LEDs, however, are able to completely dim selective areas or the entire image. Because of the relative cost-effectiveness to produce PDPs of the same size as a given LCD panel, plasma displays historically enjoyed more popularity in the larger-monitor market.  That advantage is all but gone today, resulting in more LCDs being sold today than plasma displays. 

OLED Displays

Organic light emitting diode (OLED) displays, unlike LED displays, really are the image- producing parts of the display, not just the light source. In much the same way as a plasma cell places an excitable material between two electrodes, OLEDs are self-contained cells that use the same principle to create light. An organic light-emitting compound forms the heart of the OLED and is placed between an anode and a cathode, which produce a current that runs through the electroluminescent compound, causing it to emit light. An OLED, then, is the combination of the compound and the electrodes on each side of it. The electrode in the back of the OLED cell is usually opaque, allowing a rich black display when the OLED cell is not lit. The front electrode should be transparent to allow the emission of light from the OLED. As with LCD panels, OLED panels can be classified as active matrix (AMOLED) or passive matrix (PMOLED).  As you might expect, AMOLED  displays have better  quality than  PMOLED  displays but, as a result, require  more electrodes,  a pair for each OLED. AMOLED displays have resolutions limited only by how small the OLEDs can be made, while the size and resolution of PMOLED displays are limited by other factors, such as the need to gang the electrodes for the OLEDs.  

The power to drive an OLED display is, on average, less than that required for LCDs. However, as the image progresses toward all white, the power consumption can increase to two or three times that of an LCD panel. Energy efficiency lies in future developments as well as the display of mostly darker images, which is a reason why darker text on lighter backgrounds may give way to the reverse, both in applications and online. For OLEDs, the display of black occurs by default when the OLED is not lit and requires no power at all. Although the early materials used in OLEDs have demonstrated drastically shorter life spans than those used in LCD and plasma panels, the technology is improving and has given rise to compounds that allow commercially produced OLEDs to remain viable long past the life expectancy of other technologies. The cost of such panels will continue to decrease so that purchases by more than corporations and the elite can be expected. Two important enhancements to AMOLED technology have resulted in the development of the Super AMOLED and Super AMOLED Plus displays, both owing their existence to Samsung. The Super AMOLED  display removes the standard touch sensor panel (TSP) found in the LCD and AMOLED  displays and replaces it with an on-cell TSP that is flat and applied directly to the front of the AMOLED  panel, adding a mere thousandth of a millimeter to the panel’s thickness.  The thinner TSP leads to a more visible screen in all lighting conditions and more sensitivity when used with touch panels. 

Projection Systems

Another major category of display device is the video projection system, or projector. Portable projectors can be thought of as condensed video display units with a lighting system that projects the VDU’s image onto a screen or other flat surface for group viewing. Interactive white boards have become popular over the past decade to allow presenters to project an image onto the board as they use virtual markers to electronically draw on the displayed image. Remote participants can see the slide on their terminal as well as the markups made by the presenter. The presenter can see the same markups because the board transmits them to the computer to which the projector is attached, causing them to be displayed by the projector in real time. 

Adjusting Display Settings

Although most monitors are automatically detected by the operating system and configured to the best quality that they and the graphics adapter support, sometimes manually changing display settings, such as for a new monitor or when adding a new adapter, becomes necessary. Let’s start by defining a few important terms: 
  • Refresh rate 
  • Resolution 
  • Multiple  displays 
  • Degauss 

Each of these terms relates to settings available through the operating system by way of display-option settings or through the monitor’s control panel (degauss). 


Refresh Rate

The refresh rate is technically the vertical scan frequency and specifies how many times in one second the scanning beam of electrons redraws the screen in CRTs. The phosphors stay bright for only a fraction of a second, so they must constantly be hit with electrons to appear to stay lit to the human eye. Measured in screen draws per second, or Hertz, the refresh rate indicates how much effort is being put into keeping the screen lit. The refresh rate on smaller monitors, say 14 to 16 inches, does fine in the range 60Hz to 72Hz. However, the larger a monitor gets (the more dot phosphors it has), the higher the refresh rate needs to be to reduce eye strain and perceivable flicker. It is not uncommon to see refresh rates of 85Hz and higher. Refresh rates apply to LCDs as well. For televisions, the refresh rate is a characteristic of the LCD, generally not an adjustment to be made. LCD televisions that support 120Hz refresh rates are common, but it’s easy to find those rated for 60Hz, 240Hz, and 480Hz as well. For computer monitors, you might be able to select among multiple refresh rates because you’re in control of the circuitry driving the refresh rate, the graphics adapter. However, because LCDs do not illuminate phosphors, there is no concern of pixel decay (for which refreshing the pixel is necessary). Instead, higher refresh rates translate to more fluid video motion.  Think of the refresh rate as how often a check is made to see if each pixel has been altered by the source. If a pixel should change before the next refresh, the monitor is unable to display the change in that pixel. 

Resolution 

Recall that resolution is represented as the number of horizontal dots by the number of vertical dots that make up the rows and columns of your display. There are software and hardware resolutions. Setting the resolution for your monitor is fairly straightforward. If you are using an LCD, for best results you should use the monitor’s native resolution, discussed later in this chapter.  Some systems will scale the image to avoid distortion, but others will try to fill the screen with the image, resulting in distortion. On occasion, you might find that increasing the resolution beyond the native resolution results in the need to scroll the Desktop in order to view other portions of it. In such instances, you cannot see the entire desktop all at the same time. The monitor has the last word in how the signal it receives from the adapter is displayed.  Adjusting your display settings to those that are recommended for your monitor can alleviate this scrolling effect. 

Multiple Displays 

Whether regularly or just on occasion, you may find yourself in a position where you need to use two monitors on the same computer simultaneously. For example, if you are giving a presentation and would like to have a presenter’s view on your laptop’s LCD but need to project a slide show onto a screen, you might need to connect an external projector to the laptop. Simply connecting an external display device does not guarantee it will be recognized and automatically work. You might need to change settings for the external device, such as the resolution or the device’s virtual orientation with respect to the built-in display, which affects how you drag objects between the screens.  Microsoft calls its multi-monitor feature Dual View. You have the option to extend your desktop onto a second monitor or to clone your desktop on the second monitor. You can use one graphics adapter with multiple monitor interfaces or multiple adapters. However, as of Vista, Windows Display Driver Model (WDDM) version 1.0 required that the same driver be used for all adapters. This doesn’t mean that you cannot use two adapters that fit into different expansion slot types, such as PCIe and AGP. It just means that both cards have to use the same driver. Incidentally, laptops that support external monitors use the same driver for the external interface as for the internal LCD attachment. Version 1.1, introduced with Windows 7, relaxed this requirement. WDDM is a graphics-driver architecture that provides enhanced graphics functionality that was not available before Windows Vista, such as virtualized video memory, preemptive task scheduling, and sharing of Direct3D surfaces among processes. 

Video Standards

The early video standards differ in two major areas: the highest resolution supported and the maximum number of colors in their palette.  The supported resolution and palette size are directly related to the amount of memory on the adapter, which is used to hold the rendered images to be displayed.  Display adapters through the years can be divided into five primary groups:  

  • Monochrome 
  • CGA 
  • EGA 
  • VGA 
  • DVI, HDMI,  and other modern  digital video 
  • Monochrome

The first video technology for PCs was monochrome (from the Latin mono, meaning one, and Chroma, meaning color). This black-and-white video (actually, it was green or amber text on a black background) was fine for the main operating system of the day, DOS. DOS didn’t have any need for color. Thus, the video adapter was very basic. The first adapter, developed by IBM, was known as the Monochrome Display Adapter (MDA). It could dis- play text but not graphics and used a resolution of 720n350 pixels. The Hercules Graphics Card (HGC), introduced by Hercules Computer Technology, had a resolution of 720n350 and could display graphics as well as text. It did this by using two separate modes: a text mode that allowed the adapter to optimize its resources for displaying predrawn characters from its on-board library and a graphics mode that optimized the adapter for drawing individual pixels for onscreen graphics.  It could switch between these modes on the fly. These modes of operation have been included in all graphics adapters since the introduction of the HGC. 

  • CGA 

The next logical step for displays was to add a splash of color. IBM was the first with color, with the introduction of the Color Graphics Adapter (CGA).  CGA displays 16-color text in resolutions of 320n200 (40 columns) and 640n200 (80 columns), but it displays 320n200 graphics with only four colors per mode. Each of the six possible modes has 3 fixed colors and a selectable 4th; each of the 4 colors comes from the 16 used for text. CGA’s 640n200 graphics resolution has only 2 colors—black and one other color from the same palette of 16. 

  • EGA

After a time, people wanted more colors and higher resolution, so IBM responded with the Enhanced Graphics Adapter (EGA).  EGA could display 16 colors out of a palette of 64 with CGA resolutions as well as a high-resolution 640n350 mode. EGA marks the end of classic digital-video technology. The digital data pins on the 9-pin D-sub-miniature connector accounted for six of the nine pins. As a solution, analog technologies, starting with VGA, would all but stand alone in the market until the advent of DVI and HDMI. 

  • VGA

With the PS/2 line of computers, IBM wanted to answer the cry for “more resolution, more colors” by introducing its best video adapter to date: the Video Graphics Array (VGA). This video technology had a “whopping” 256KB of video memory on board and could display 16 colors at 640n480, 640n350, and 320n200 pixels or, using mode 13h of the VGA BIOS, 256 colors at 320n200 pixels. It became widely used and enjoyed a long reign as at least the base standard for color PC video. For many years, it was the starting point for computers, as far as video is concerned. Until recently, however, your computer likely defaulted to this video technology’s resolution and color palette only when there was an issue with the driver for your graphics adapter or when you entered Safe Mode.  Today, even these modes display with impressive graphics quality. One unique feature of VGA (and its offshoots) is that it’s an analog technology, unlike 


The preceding and subsequent standards. Technically, the electronics of all graphics adapters and monitors operate in the digital realm. The difference in VGA-based technologies is that graphics adapters output and monitors receive an analog signal over the cable. Conversely, MDA, CGA, EGA, HDMI, and DVID signals arrive at the monitor as digital pulse streams with no analog-to-digital conversion required. VGA builds a dynamic palette of 256 colors, which are chosen from various shades and hues of an 18-bit palette of 262,114 colors. When only 16 colors are displayed, they are chosen from the 256 selected colors. VGA sold well mainly because users could choose from almost any color they wanted (or at least one that was close). The reason for moving away from the original digital signal is because for every power of 2 that the number of colors in the palette increases, you need at least one more pin on the connector. A minimum of 4 pins for 16 colors is not a big deal, but a minimum of 32 pins for 32-bit graphics become a bit unwieldy.  The cable has to grow with the connector, as well, affecting transmission quality and cable length. VGA, on the other hand, requires only 3 pins, one each for red, green, and blue modulated analog color levels, not including the necessary complement of ground, sync, and other control signals. For this application, 12 to 14 of the 15 pins of a VGA connector are adequate. 

More Recent Video Standards

Any standard other than the ones already mentioned are probably extensions of SVGA or XGA. It has becoming quite easy to predict the approximate or exact resolution of a video specification based on its name. Whenever a known technology is preceded by the letter W, you can assume roughly the same vertical resolution but a wider horizontal resolution to accommodate 16:10 wide-screen formats (16:9 for LCD and plasma televisions). Preceding the technology with the letter Q indicates that the horizontal and vertical resolutions were each doubled, making a final number of pixels 4 times (quadruple) the original. To imply 4 times each, for a final resolution enhancement of 16 times, the letter H for hexadecatuple is used. Therefore, if XGA has a resolution of 1024n768, then QXGA will have a resolution of 2048n1536. If Ultra XGA (UXGA) has a resolution of 1600n1200 and an aspect ratio of 4:3, then WUXGA has a resolution of 1920n1200 and a 16:10 aspect ratio. Clearly, there have been a large number of seemingly minute increases in resolution column and row sizes. However, consider that at 1024n768, for instance, the screen will display a total of 786,432 pixels. At 1280n1024, comparatively, the number of pixels increases to 1,310,720—nearly double the pixels for what doesn’t sound like much of a difference. As mentioned, you need better technology and more video memory to display even slightly higher resolutions. 

Name

Resolutions
Colors
Monochrome Display Adapter (MDA)
720 n350
Mono (text  only)
Hercules Graphics Card  (HGC)
720 n350
Mono (text  and graphics)
Color  Graphics Adapter (CGA)
320 n200
4

640 n200
2
Enhanced Graphics Adapter (EGA)
640 n350
16
Video  Graphics Array  (VGA)
640 n480
16

320 n200
256
ATSC 480i /480p, 4:3 or 16:9
704n480
Not specified
Super VGA (SVGA)
800 n 600
16
Extended Graphics Array  (XGA)
800 n 600
65,536

1024n768
256
Widescreen XGA (WXGA), 16:10
1280 n 800
Not specified
Super XGA (SXGA), 5:4
1280 n1024
Not specified
ATSC 720p, 16:9
1280 n720
Not specified
SXGA+
1400 n1050
Not specified
WSXGA+,  16:10
1680 n1050
Not specified
Ultra  XGA (UXGA)
1600 n1200
Not specified
WUXGA, 16:10
1920 n1200
Not specified
ATSC 1080i /1080p, 16:9
1920 n1080
Not specified
Quad XGA (QXGA)
2048 n1536
Not specified
WQXGA, 16:10
2560 n1600
Not specified
WQUXGA,  16:10

 3840 n2400

Not specified

WHUXGA, 16:10
7680 n4800
Not specified

Starting with SXGA, the more advanced resolutions can be paired with 32-bit graphics, which specifies the 24-bit True-color palette of 16,777,216 colors and uses the other 8 bits for enhanced no features, if at all. In some cases, using 32 bits to store 24 bits of color information per pixel performance because the bit boundaries are divisible by a power of 2; 32 is a power of 2, but 24 is not. That being said, however, unlike with the older standards, the color palette is not officially part of the newer specifications. 

Nonadjustable Characteristics

The following sections discuss features that are more selling points for display units and not configurable settings. 

Native Resolution

One of the peculiarities of LCD, plasma, OLED, and other flat-panel displays is that they have a single fixed resolution, known as the native resolution. Unlike CRT monitors, which can display a crisp image at many resolutions within a supported range, flat-panel monitors have trouble displaying most resolutions other than their native resolution. The native resolution comes from the placement of the transistors in the hardware display matrix of the monitor. For a native resolution of 1680n1050, for example, there are 1,764,000 transistors (LCDs) or cells (PDPs and OLED displays) arranged in a grid of 1680 columns and 1050 rows. Trying to display a resolution other than 1680n1050 through the operating system tends to result in the monitor interpolating the resolution to fit the differing number of software pixels to the 1,764,000 transistors, often resulting in a distortion of the image on the screen. The distortion can take various forms, such as blurred text, elliptical circles, and so forth.  SXGA (1280n1024) was once one of the most popular native resolutions for larger LCD computer monitors before use of wide-screen monitors became pervasive. For wide- screen aspects, especially for wide-screen LCD displays of 15.4 g and larger, WSXGA+ (1680n1050) was one of the original popular native resolutions. The ATSC 1080p resolution (1920n1080) is highly common today across all display technologies, largely replacing the popular computer-graphics version, WUXGA (1920n1200). 

Contrast Ratio

The contrast ratio is the measure of the ratio of the luminance of the brightest color to that of the darkest color the screen is capable of producing. Do not confuse contrast ratio with contrast.  Contrast ratios are generally fixed measurements that become selling points for the monitors. Contrast, on the other hand, is an adjustable setting on all monitors (usually found alongside brightness) that changes the relative brightness of adjacent pixels. The more contrast, the sharper and edgier the image. Reducing the contrast too much can make the image appear washed out. This discussion is not about contrast but instead contrast ratio. One of the original problems with LCD displays, and a continuing problem with cheaper versions, is that they have low contrast ratios.  Only LED-back-lit LCD panels rival the high contrast ratios that plasma displays have always demonstrated. A display with a low contrast ratio won’t show a “true black” very well, and the other colors will look washed out when you have a light source nearby.  Try to use the device in full sunshine and you’re not going to see much of anything, although the overall brightness level is the true key in such surroundings. Also, lower contrast ratios mean that you’ll have a harder time viewing images from the side as compared with being directly in front of the display. Ratios for smaller LCD monitors and televisions typically start out around 500:1. Common ratios for larger units range from 20,000:1 to 100,000:1. In the early days of monitors that used LEDs as back-lights, 1,000,000:1 was exceedingly common.  Today, vendors advertise 10,000,000:1 and “infinite” as contrast ratios.  Anything higher than 32,000:1 is likely a dynamic contrast ratio.  Plasma displays have always been expected to have contrast ratios of around 5,000:1 or better. 

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