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Lesson 4.8 The screen and graphics card
Introduction
The screen
Specifications screens
The display adapter (video card)
Features graphics cards
When you study this lesson you will:
• To describe how a screen
• state the basic characteristics of a screen
• To describe the operating principle of the graphics card
• To mention the main features of a graphics card
4.8.1. Introduction
As we have seen, one of the key parts of the personal computer is the screen (monitor). The screen is a separate device from the PC and connects to the central unit by using a special cable. To connect the monitor to the motherboard is necessary to use a special expansion card. This expansion card called display adapter (Display Adapter) or else video card (Graphics Card). The graphics card has a socket on which is connected via the cable mentioned above, the screen.
4.8.2. The screen
The screen is the main output device of the personal computer. Through this we get almost all the information you need from your computer. So we see on screen the results of the computer instruction for the user to continue data entry and data on the state of the computer. When we assemble a personal computer, it is very important to select the appropriate screen. The choice must be made in accordance with the work that will use the personal computer, having in mind the cost. So for example if the personal computer will be used almost exclusively for word processing, can be selected a relatively cheap and small screen. Conversely, if the personal computer to be used by a graphic designer for magazine cover design, a choice must be very good quality, large and therefore expensive monitor. Then we see the key characteristics of a screen and how they affect the quality and ergonomics.
4.8.3. Specifications screens
Just how good a quality screen and how much is appropriate for a job depends on the technical characteristics. Depending upon the use intended for the screen, some of these technical features are more and others less important. For this reason the choice of the screen should always be guided by the needs of the user's personal computer.
Display technology
The screens of personal computers are divided into two main categories: CRT (Cathode Ray Tube - CRT) and flat screens.
The CRT monitor uses the same imaging technique with the TV. At one end of a tube, called a cathode ray tube, there are three electron guns, one for each of the three colors (blue, red and green). With these colors suitable combinations can be displayed on the screen a very large number of colors. Each of these guns emit an electron beam which is deflected by a suitable magnetic field to scan a screen. This screen is coated with a phosphor which glows when it falls on the beam of electrons. This process is very fast that the human eye can not manage to see the trace of the electron beam on the screen but a complete picture.
Flat screens are mainly based on liquid crystal technology. In these screens a thin layer of liquid crystals. With special electronic devices have the potential to change the polarization of these crystals thus changing the way we let the light pass through them. In this way we can polarize the crystals of a suitable screen, thus creating the image we want.
Flat screens have a much smaller volume than the CRT. It is also much lighter and have much lower power consumption, properties that make them ideal for notebooks where these sizes are critical. The CRT, however, compared with flat screens have a much better image quality and lower price, so preferred to desktop computers.
Size
One of the most important technical characteristics of a screen is the size. The higher this figure, the more information can visualize the screen. Also, the sharpness of the screen is better the larger the size of the latter. The size of a screen measured in inches (") and expresses the long diagonal of the screen. On CRT monitors this length is the length of the diagonal of the picture tube and not the diagonal of the image you can see. The length of the diagonal image is usually 1 "to 1.5" lower. Thus, such a screen size of 15 "may actually show a picture with a diagonal 14" or less. Typical sizes for CRT is 14 ", 15", 17 "19" and 21 ", but the figure may be up to 42". Unlike the size of flat panel displays corresponding to the actual length of the diagonal of the image can be shown.
Analysis
The analysis of a screen is the number of different elements or pixels (pixel = Picture Element - image data) that can be used to synthesize an image on the screen. The analysis of the screen informs us about how many elements can exist in the horizontal and the vertical axis. Thus, a screen resolution of 800X600 can show an image with 800 points on the horizontal axis and 600 points on the vertical axis, a total of 480,000 items. Typical analyzes used in the screens of personal computers is 640X480, 800CH600, 1024CH768, 1280X1024 and 1600CH1200. The ratio of horizontal to vertical resolution is kept constant to avoid a distorted picture when displayed on the screen with different resolutions.
Figure 4.8.2: A picture on the computer screen consists of a number of discrete elements (pixels). When the screen resolution is big (ie the pixels are small), the human eye has difficulty distinguishing the "rungs" in the picture.
The CRT monitors are usually able to work with many different analyzes. In general, the larger the size of a CRT screen, the higher the maximum resolution with which to work. In contrast, flat screens can be operated only with a specific resolution that is defined by the manufacturer of the screen.
Step dot
A screen to display different colors used for each element of the image triplets of dots. Each dot is one of a trio of three pure colors (blue, red and green) that can show the screen. Because these dots are very close to each other, the human eye can not distinguish them, thus seeing only one color is the color combination of three dots. Thus, depending on the intensity of each dot can be visualized million color combinations. Step dot (dot pitch) of a screen is the distance that the dots have a trio together and measured in millimeters (mm). The smaller the dot step as a screen cleaner colors seem a more difficult that the human eye to distinguish the dots of the triad. Typical values for the step bullet is 0,22 mm in 0,28 mm. Monitors larger dot pitch of 0,28 mm have a very poor image quality and is not recommended for use.
Refresh Rate
The refresh rate (refresh rate) the number of times renewed the image of the screen every second and is measured in Hz (1 Hz = 1 time per second). If this rate is low, then the human eye can not understand the alternation of successive images so the screen flicker, which fatigues the computer user. When the refresh rate is high, the display appears stable and relaxed. Typical values of the refresh rate is 56Hz to 160Hz. Generally, the greater the resolution of a specific monitor both shortens the refresh rate. So for example, can a 640X480 screen resolution has 120Hz refresh rate and resolution 1024CH768 have refresh rate 75Hz. The better and therefore more expensive is a screen, the higher refresh rates can have on various analyzes. A screen refresh rate of 60Hz or less tedious as it is noticeable flicker. A screen to be relaxing, you must refresh rate is 75Hz or higher.
4.8.4. The display adapter (video card)
The video adapter is an electronic circuit that is used to connect the monitor to the motherboard. The personal computer can not function without a screen to communicate with the user. So the graphics adapter circuitry is absolutely necessary for the operation of personal computer. For this reason many PC manufacturers choose to integrate the circuits on the motherboard of the computer. The formulations baby AT motherboards and ATX however (see section 4.2.5) does not allow the installation of such circuits on the motherboard. In these cases, the video adapter card is in the form of expansion and for this reason called the graphics card. The design has a major advantage. We can choose between many different graphics card options that best suit the needs of the user.
The principle function of a graphics card is relatively simple: Each graphics card has a memory RAM, in which the personal computer processor writes the data it wants to portray on screen. Then there are special circuits to the graphics card read data and produce appropriate signals which are sent to the screen to create the desired image. The signals are analog, as opposed to computer data is digital. For this reason, any graphics card is a converter from digital to analog (DAC - Digital to Analog Converter) that converts digital computer data to analog signals needed by the monitor to work.
Figure 4.8.4: Operation of standard graphics card
Modern graphics cards usually have a special processor, graphics accelerator. This particular processor is able to accept the description of objects two or three dimensions and then creates a very high speed data to the image. So far the accelerated imaging process, one that the processor of the PC should simply describe the objects that would be displayed and the "heavy lifting" of the display makes graphics accelerator that is specialized for this task.
4.8.5. Features graphics cards
Each graphics card has a number of characteristics that define the capabilities and the use for which intended. The main features of a graphics card are described below.
Analysis
Each graphics card can support a number of analyzes. The analysis (resolution) of a graphics card is the number of pixels that can be used to synthesize an image on the screen. Typical analyzes used in graphics cards for PCs are 640X480, 800CH600, 1024CH768, 1280X1024 and 1600CH1200.
Color Depth
The color depth (color depth) is measured in bits, and is the number of different colors can be any pixel. Typical values for the color depth is 8 bits (28 = 256 different colors), 16 bits (216 = 65.536 different colors), 24 bits (224 = 16.777.216 different colors) and 32 bits (232 = 4.294.967.296 different colors) .
Memory
The graphics card memory is RAM memory and is used to write the editor of the PC data wants to be visualized on the screen. The graphics card memory is directly related to the resolution and color depth, one to describe each pixel of the image should be used as many bits as defined by the color depth. So, for example to display an image analysis 800CH600 = 480.000 pixels with 24 bits color depth required memory 480.000pixels X 24bits/pixel / 8 bits / Byte = 1.440.000 Bytes. The higher the memory the better graphics card and color depth analyzes can support. Typical values for the graphics card memory is 1 MByte, 2 MBytes, 4 MBytes, 8 MBytes, 16 MBytes, and 32 MBytes.
Refresh Rate
The refresh rate (refresh rate) of the image on the screen depends on the graphics card. So a graphics card for each analysis supports up a maximum refresh rate.
Type corridor for regional
Graphics cards are available for almost all types of regional corridors. But because the amount of information to be transferred from the processor to the graphics card memory for each image is great, good graphics cards use either the treadmill or the treadmill PCI AGP. Modern graphics cards use almost exclusively the treadmill AGP, which as we saw in lesson 4.6 was designed specifically for the demands of graphics cards.
What did you learn
• The display plugs into the motherboard via the graphics card.
• The main categories are two screens: CRT monitors and flat screens.
• The size of a screen measured in inches, and is the diagonal of the image to display.
• The higher the resolution of a display so much information to display.
• Step dot is a measure of sharpness of the screen.
• The video card converts the digital data processor to signals suitable for display.
Terminology
• CRT monitor, flat screen
• analysis, pixel
• Step dot, refresh rate
• graphics card, display adapter, graphics accelerator
• Color Depth
Control knowledge
1. What function performed by the graphics card in a PC?
2. How does a CRT monitor and that a flat screen?
3. What advantages have CRT monitors and flat screens are what?
4. What is the screen resolution?
5. What is the dot step and why it is important to be as small as possible?
6. Why display a low refresh rate can be tedious?
7. How does a graphics card? What is the role of circuit DAC;
8. Calculate how much memory should have a graphics card to display an image with a resolution and color depth 1024CH768 16 bits.
