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Voice input



Today you can also interact with your computer by voice with a voice-recognition system that converts voice into text, so you can dictate text directly onto your word processor or email program. You can also control your PC with voice commands; this means you can launch programs, open, save or print files. Some systems let you search the "Web or chat using your voice instead of the keyboard.

Output devices are also very important, they allow us to get the processed information. The examples of output devices are printers and display screens. The screen of a computer is often known as the monitor or VDU (visual display unit).Inside the computer, there is a video card which processes images and sends the signals to the monitor. When choosing a monitor, you have to take into account a few basics.

· Type of display- the choice is between CRT or an LCD screen. The Cathode Ray Tube of a monitor is similar to a traditional TV set. It has three electron guns (one for each primary colour: red,green,blue) that strike the inside of the screen, which is coated with substances called phosphors, which glow and create colours. CRTs are cheap, but they are heavy, can flicker and emit radiation. A Liquid Crystal Display is made from flat plates with a liquid crystal solution between them. The crystal block the light in different quantities to create the image. Active – matrix LCDs use TFT (thin film transistor) technology, in which each pixel has its own transistor switch. They offer better quality and take up less space, so they are replacing CRTs.

· Screen size – the viewing area is measured diagonally; in other words, a 17” screen measures 17 inches from the top left corner to the bottom right.

· Resolution – the clarity of the image depends on the number of pixels (short for picture elements) contained on a display, horizontally and vertically. A typical resolution is 1,024x768. The sharpness of images is affected by dot pitch, the distance between the pixels on the screen, so a dot pitch of 0.28 mm or less will produce a sharp image.

· Brightness – the luminance of images is measured in cd/m2 (candela per square metre)

· Colour depth – the number of colours a monitor can display. For example, a VGA monitor produces 256 colours, enough for home use; a Super VGA can produce up to 16.7 million colours, so is ideal for photographic work and video games.

· Refresh rate – the number of images that the image is drawn each second. If a monitor has refresh rate of 75 Hertz (Hz), it means that the screen is scanned 75 times per second. If this rate is low, you will notice a flicker, which can cause eye fatique.

Exercise 1. Which input device would you use for these tasks?

1. To play computer games

2. To copy images from paper into a computer

3. To read price labels in a shop

4. To select text and click on links on web pages

5. To enter drawings and sketches into a computer

6. To input voice commands and dictate text

7. To draw pictures or select menu options directly on the screen

8. To take and store pictures and then download them to computer

Exercise 2. Complete each sentence by choosing from the following devices:





Дата публикования: 2015-02-22; Прочитано: 739 | Нарушение авторского права страницы | Мы поможем в написании вашей работы!



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