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Monitors

April 4th, 2009
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INTRODUCTION

The monitor is the main output device. It is called by many other names such as screen, display, video display and video display terminal.

There are different types of monitors. Common monitors for the PC include monochrome, CGA ( Color Graphics Array), SVGA ( Super Video Graphics Array, and XGA (Extended Graphics Array). Of these the SVGA is the most common.

This lecture on printers focuses on:

1. Types of Monitors
2. Two Main Charistics
3. How Pictures are formed
4. Graphics Adapter / Card
5. Interlaced and Non-interlaced
6. Refresh rate
7. CRT vs LCD

Types of Monitors

There are two main types of monitors :

• Interlace
• Non-interlace

Interlace MONITORS

Interlaced monitors must make two passes to display an image and because of this they flicker. Noninterlaced monitors make only one pass and do not flicker.

The two most important characteristics of any monitor are :

1. The number of colours it displays
2. The clarity of the images produced

Graphics Adapter

The graphics adapter card also called the video card or graphics board determines the representation of colour and resolution. This card is placed in the chassis and it is to this card the monitor is connected.

Refresh Rate

Another very important feature of a monitor is its Refresh rate which is a term used to define how many times per second a display is refreshed. The rate depends on the type of video card and monitor you're using, and can usually be changed in the display properties.

If possible, choose a refresh rate or 75Hz or higher because this is much easier for your eyes to handle. It's not uncommon to see refresh rates of over 100Hz in some high-end configurations.

How a Picture is formed

Images are made up of tiny dots called picture elements or pixels . A pixel is the smallest unit on the screen that can be turned on or off. The more pixels in a given area will result in sharper images. This feature is called the resolution of the monitor. If a screen has a resolution of 1024 X 768 this means that the screen has 1024 rows and 768 columns of pixels. The higher the resolution the clearer and crisper the image.

CRT vs LCD

Older monitors are based on cathode ray tube technology ( CRT ). The same technology used to display images on a television set. They are bulky but less expensive than the newer LCD ( Liquid Crystal Display) technology with provides flater screens with great quality.

In a CRT monitor, an electron beam in a vacuum tube, or a "raster" as it is known, is magnetically drawn back and forth to create a pattern on a layer of phosphor behind the curved screen. The electrons excite the phosphor, and by modulating the intensity of the beam, an image is created.

The LCD works differently. Its flat-panel display has a matrix structure. Every pixel or picture element has a flat or uniform backlight. A sheet of liquid crystal acts like a valve, passing more or less of the backlight onto the screen, creating an image or pattern.

GENERAL FACTS

The EYES Have it

Many users seem to get carried away with the CPU speed and too little attention is paid to the monitor. It is far better to invest more in a high quality monitor that produces crisp, clear images than to run after a computer with the fastest CPU. Users need to pay more attention to the health of their own eyes when using a computer.

The trend is now towards LCD so consider these when next you need a monitor.

SUMMARY

1. The two main types of monitors are interlaced and non-interlaced
2. A high quality graphics card is needed for sharp images
3. A pixel is the smallest unit on the screen that can be turned on or off.
4. The number of pixels determine the resolution.
5. Slim LCD monitors are fast replacing bulky CRT monitors on PCs

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