A+ Essentials Tutorial
1.0 Personal Computer Components
Cathode Ray Tube (CRT):
Figure: CRT cross sectional diagram showing important components of a CRT.
There are two types of cathode ray displays. One is non-interlaced, and the other is interlaced. Normally, all the displays are interlaced to reduce flicker.
As shown in the figure, for non-interlaced display, the scanning is done continuously from top to bottom. For non-interlaced display, alternate rows are scanned.
A black and white monitor contains only one electron gun, whereas a color display monitor will have three electron guns, each of which represent red, green, and blue.
The horizontal and vertical deflection takes place by applying appropriate voltages to the horizontal, and vertical deflection plates. Usually, the screen is refreshed between 60-100 times per second.
The grid shown in the figure controls the speed with with the electrons hit the screen. If a positive voltage is applied to the screen grid, because of which the electrons are accelerated and hit the screen, making the screen brighter. If a negative voltage is applied to the grip, the electrons are decelerated and the screen will not glow. The microscopic control of electron beam flow, produces images on the screen.
One basic unit of measurement is "pixel" and stands for "picture element". A pixel is the smallest area in a graphics display that can be manipulated.
Given below are the commonly used screen resolutions:
Screen resolution is always stated as the horizontal number of pixels by the vertical number of pixels. A screen displaying 800 x 600 pixels has 600 rows, each 800 pixels wide.
Graphics Cards: The graphics card resides in the CPU box, and drives the video display. A typical graphics card is shown below:
The graphics card shown includes DVI connector, TV/Video connector, and a VGA connector. The card has an on-board graphics processor with cooling fan. Usually, for graphic intensive applications, you need a higher end graphic adapter card. For normal desktop usage, a video adapter will be sufficient.
LCD monitors, as their name suggests, use liquid crystal display (LCD) technology. The LCD technology is very different form CRT technology. An LCD is a thin and flat display device compared to bulky, and heavy CRT.
LCD crystals are liquid chemicals that allow light to pass through themselves when aligned. By using electrical currents to varying degrees to align the crystals, it is possible to create the desired images and colors.
The liquid crystals are suspended between two pieces of polarized glass ("substrate"). The fluorescent light source emanates light that passes through the first substrate. The electrical currents then cause the crystals to align, allow varying levels of light to pass through to the second substrate, resulting in desired images being shown on the LCD screen.
There are two types of LCDs:
Most LCD monitors, along with LCD TVs, use active-matrix.
As with CRT, a pixel is a single point in a graphic image in CRT, and stands for "picture element". Each pixel on an LCD monitor comprises of three cells, red, green, and blue.
The projector is useful when you need to show the contents of your seminar or lecture to a wider audience. A projector is almost always seen in any boardroom or a conference room.
There are primarily three types of projectors: LCD, DLP, and CRT
CRT projectors are bulkier, and difficult to carry. These are hardly used in modern Projectors due their size. The disadvantage with DLP is its high cost.
Important parameters that you need to see when selecting a projector are:
Connector types (e.g. VGA, DVI / HDMi, S-Video, Component / RGB)
15 PIN HIGHDENSITY D-SUB MALE at the monitor cable.
The Digital Display Working Group (DDWG) has developed the Digital Visual Interface (DVI) as a video interface standard to maximize the visual quality of digital display devices (eg. flat panel LCDs, and digital projectors). DVI-D is compatible with HDMi standard.
There are three types of DVI connector:
The connector also includes provision for a second data link for high resolution displays. This type of connector is referred to as DVI-DL (dual link).
The High-Definition Multimedia Interface (HDMI):
This is an all-digital audio/video interface that provides connectivity between any compatible digital audio/video source, such as a set-top box, a DVD player, a PC, or a video game console and a compatible digital audio and/or video monitor, such as a digital television (DTV).
It is considered as a replacement for older standards such as RF - coaxial cable, S-Video, VGA, and DVI. HDMI is backward compatible with the single-link Digital Visual Interface carrying digital video (DVI-D or DVI-I, but not DVI-A) used on computer monitors and graphics cards.
S-Video, short for "Separate Video", is an analog video signal that carries the video data as two separate signals (brightness and color), unlike composite video which carries the entire set of signals in one signal line. The 4-pin Mini-DIN connector (shown at right) is the most common of several types of S-Video connectors.
S-video does not carry audio on the same cable. It is mostly used to output a PC's video signal to a Television.
Settings (e.g. V-hold, refresh rate, resolution)
V-Hold adjusts Vertical Hold. Use this if screen is having uncontrollable scrolling.
The refresh rate (or "vertical refresh rate", "vertical scan rate" for CRTs) is the number of times that the screen is refreshed. This is distinct from the measure of frame rate in that the refresh rate includes the repeated refreshment of identical frames, while frame rate measures how often a display can change from one image to another.
For example, a movie projector advances from one frame to another 24 times each second. But each frame is refreshed twice before the next frame is projected. As a result, the movie projector runs at 24 frames per second, but has a 48 Hz refresh rate.
To change the refresh frequency for your monitor (Windows 2000 OS):
1. Open Display dialog box in Control Panel.
Resolution refers to the number of individual pixels
contained in a screen display. Resolution is expressed by identifying the
number of pixels on the horizontal axis (rows) and the number on the
vertical axis (columns), such as 1024x768. Monitor size and screen
resolution work together to determine the physical size of objects displayed
on the screen. Commonly used screen resolutions include 640x480, 800x600,
1024x768, 1152x864, 1280x1024, and 1600x1200.
1. Open Display dialog box in Control Panel.
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