Unit 4. Input, output devices

Focus: Input and output devices.

Grammar focus: Gerund with prepositions.

Skills focus: Reading for specific information to know about input and output devices.

Before reading:

Discuss the question: “How is it possible to interact with computer?”Read the information about input and output devices.

There are some input and output devices. Let us start with input devices. Input devices are the pieces of hardware which allow us to enter information into the computer, for example, a keyboard, a mouse, a voice recognition systems, scanners and cameras.

The keyboard

A standard PC keyboard has various groups of keys.

· Alphanumeric keys – these represent letters and numbers, arranged as on a typewriter.

· A numeric keypad appears to the right of the main keyboard and contains numeric and editing keys; the Num Lock key is used to switch from numbers to editing functions.

· Function keys appear at the top of the keyboard and can be programmed to do special jobs.

· Cursor keys include 'arrow keys' which move the insertion point, and keys such as Home, End, Page Up, and Page Down, which let you move around documents.

· Dedicated keys are used to issue commands or produce alternative characters. For example; Ctrl changes the functions of other keys (e.g. Ctrl + X cuts the selected text).

Caps Lock sets the keyboard in 'CAPITALS' mode; it only affects
letters.

Enter (or Return) is pressed to select options from a menu or to start a new paragraph.

Backspace deletes the character to the left of your current position.

The mouse

A mouse is a hand-held device that lets you move a pointer (or cursor) and select items on the screen. It has one or more buttons to communicate with the PC. A scroll wheel lets you move through your documents or web pages The pointer looks like an I-bar, an arrow or a pointing hand.

An optical mouse has an optical sensor instead of a ball underneath.

A cordless (wireless) mouse has no cable; it sends data via infrared signals or radio waves.

Mouse actions:

· to click – press and release the left button.

· to double-click – press and release the left button twice.

· to drag – hold down the button, move the pointer to a new place and then release the button.

· to right-click – press and release the right button; this action displays a list of commands.

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 phosphorus, 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 fatigue.

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: touchscreen, trackball, touchpad, webcam

1. A………. is a stationary device that works like a mouse turned upside down. You roll the ball with your hand to move the pointer on the screen.

2. Interactive……….are used in museums, information centres and Internet kiosks. You use your finger to point directly to objects on the screen.

3. A……….is used to send live video images via the Internet.

4. A……….is found on notebook PCs. You use it by pressing the sensitive pad with a finger.

 

Exercise 3. Complete these sentences with the correct 'mouse action'.

1. To start a program or open a document you………on its icon – that is, you rapidly press and release the mouse button twice.

2. If you want to select a menu option, you just……….on the left
button.

3. If you want to find the commands for a particular text, image, etc., you have to……….on it.

4. If you want to move an object, press the button and………..the object to the desired location.

 

 

Exercise 4. Read and correct the false statements.

1. The images shown on a monitor are not generated by the video card.

2. All visible colours can be made from mixing the three primary colours of red, yellow and blue.

3. Typical CRT-based displays occupy less space than LCD displays.

4. Active-matrix LCDs do not use a technology called thin film transistor or TFT.

5. The size of the screen is measured horizontally.

Exercise 5. Match each term with the correct definition.

1. phosphors	a. the frequency at which a monitor renews its image, measured in Hz
2. LCD screen	b. a flat-panel display which works by emitting light through a special liquid
3. pixel	c. the space between a display’s pixels
4. dot pitch	d. the smallest element in a displayed image
5. refresh rate	e. materials that emit light and produce colours when they are activated by an electron beam

 

Speaking

What do you think of this idea?

Some day, we’ll be talking to our PC naturally, like a friend.

Writing

Summarize the information on input and output devices for your friend who are buying a computer.