The Monitor

dot; pixel; display; resolution; cathode ray tube; hertz; refresh rate; flicker; bit-mapped; electron beam; visualize

The characters and pictures that we see on the screen are made up of dots, also called picture elements (pixels). The total number of pixels in which the display is divided both horizontally and vertically is known as the resolution. If the number of pixels is very large we obtain a high resolution display and therefore a sharp image. If the number of pixels is small, a low resolution is produced. A larger number of pixels gives a much clearer image.

The cathode ray tube of the monitor is very similar to that of a TV set. Inside the tube there is an electron beam which scans the screen and turns on or off the pixels that make up the image. The beam begins in the top left corner and scans the screen from left to right in a continuous sequence, similar to the movement of our eyes when we read but much faster. This sequence is repeated 50, 60 or 75 times per second depending on the system. If the rate of this repetition is low, we can perceive a flickering, unsteady screen, which can cause eye fatigue. However, a fast moving 75 Hz refresh rate eliminates this annoying flicker.

What we see on the screen is created and stored in an area of RAM, so that there is a memory cell allocated to each pixel. This type of display is called bit-mapped. On monochrome monitors, bits 0 are visualized as white dots, and bits 1 as black dots.

On colour displays, there are three electron guns at the back of the monitor’s tube. Each electron gun shoots out a beam of electrons strike the inside of the screen which is coated with substances called phosphors that grow when struck by electrons. Three different phosphor materials are used – one each for red, green and blue. To create different colours, the intensity of each of the three electron beams is varied.

The monitor is controlled by a separate circuit board, known as the display adapter, which plugs into the motherboard of the computer. Different boards drive different types of displays. For example, the VGA (Video Graphics Array) card has become a standard for colour monitors.

Portable computers use flat Liquid-Crystal Display instead of a picture tube. A LCD uses a grid of crystals and polarizing filters to show the image. The crystals block the light in different amounts to generate the dots in the image.

(E.C.U.)

b) Прочитайте текст еще раз и ответьте на следующие вопросы:

1. According to the writer, what is the importance of the ‘pixel resolution’?

2. Which unit of frequency to measure the refresh rate of a monitor?

3. In the writer’s opinion, why can a low refresh rate produce eye fatigue?

4. What substance is hit by electron in a monitor?

5. What is the standard display system for many PCs?

6. What does LCD stands for? What type of computers use LCD?

Упражнение 42. Как Вы знаете, существуют определенные рекомендации для людей, работающих на компьютере, которые помогают избежать переутомления, снизить вероятность нарушения зрения и т.д. Приведенные ниже правила даны в форме инструкции, однако, как известно, иногда лучше выразить их в форме совета. Измените следующие предложения по образцу:

Position your keyboard at the same height as you elbows. – You should/ought to position your keyboard at the same height as you elbows.

Don’t use a monitor that is fuzzy or distorts the image. – You shouldn’t/oughtn’t to use a monitor that is fuzzy or distorts the image.

1. Do not stare at the screen for long periods of time.

2. Avoid placing the monitor so that it reflects a source of bright light, such as a window.

3. Keep the screen clean to prevent distorting shadows.

4. If you work in an office with a large number of computers don’t sit too close to the sides or backs of monitors.

5. Buy a protective filter that cuts down the ELF (Extremely Low Frequency) emissions.

У пражнение 43.

a) Прослушайте лекцию о принтерах и заполните таблицу:

Type of printer	Advantages	Disadvantages	Notes

b) Прочитайте текст о принтерах и дополните таблицу предыдущего задания: