Vocabulary

fair and square (1ine 45-50) - honestly

it can't hurt (1ine 55-60) - it's probably a good idea

Task 2 Decide whether the following statements are true (T) or false (F) in relation to the information in the text. If you feel a statement is false, change it to make it true.

1  Viruses cannot be spread through a computer network, only via floppies transported from computer to computer.

2  The virus will spread as soon as you put the infected floppy in your PC.

3  The infector works by interfering in some way with the normal use of your computer.

4  The detonator in Lehigh works by altering what you see on your screen.

5  Most viruses spread through pirated games.

6  You should run an antivirus program every time you use your computer.

7  There are not very many viruses in circulation.

8  Virus shields are more effective than virus scanners.

Task 3 These are answers to questions about the text. Write the questions.

1. Two, one that infects and one that does the damage.

2. By interfering in some way with the normal use of the computer.

3. After it has infected four copies of COMMAND. COM.

4. Every time you access a hard disk subdirectory or a floppy disk containing COMMAND.COM.

5. Yes, by using your common sense and by occasionally scanning for them.

Task 4 Using the line reference given, look back in the text and find the reference for the words in italics.

1. They have two very (line 3)

2. is that it replicates itself (line 4)

3. enlarging it by about (line 15)

4. of itself to that file (line 23)

5. and infects it (line 32)

6. This is easy to (line 49)

7. which detect viruses (line 57)

8. once they've infected (line 59)

Task 5 Using the line references given, look back in the text and find words or phrases with a similar meaning to:

1. reproduces (lines 5-10)

2. infect (lines 5-10)

3. changing (lines 10-15)

4. immediately (lines 25-30)

5. complain (lines 35-40)

Using the line references given, look back in the text and find words or phrases that have an opposite meaning to:

6. reducing (lines 10-15)

7. removed from (lines 25-30)

8. records (lines 35-40)

9. ignorant (lines 40-45)

10. frequently (lines 40-45)

Task 6 Translate last five paragraphs (beginning 'Don't worry too much...' lines 41 - 69) into your own language.

UNIT EIGHT: 24-BIT COLOUR

Short explanation:

If your computer has 24-bit colour, then it can display photographic images in colour on its screen that have natural-looking tones.

Long, long explanation:

5 In principle, there is an infinite number of shades available between a solid colour and pure white. In practice, the human eye can detect somewhere between 150-200 distinct shades, so as long as you've got more than this, you can produce an undetectably smooth progression

of shades (there are exceptions, but they're not worth going into

10 here).

Cheapo computer monitors can't display shades - you get solid black or white and nothing else (in many cases you get black or green). It is possible to fake shades on one of these monitors by a sort of poor man's halftone process called dithering, but this is

15 useless for serious image viewing and retouching.

What you need is a computer that can show true shades on its screen. A computer builds up a picture from a series of building blocks called pixels. Each pixel is a square (normally) of a single colour. The more pixels you can divide the picture into, the higher

20 the resolution of the complete image. The computer organizes itself by describing each pixel that it wants to display as a code in the binary mathematical set (numbers built up from a series of Os or 1s). Each 0 or 1 is called a bit.

Computers are generally structured to work in groups of eight

25 bits (called a byte). These eight numbers can be used to count up to 256, and so can describe 256 shades of grey from black to white, which is more than enough to satisfy the eye.

A computer which can assign eight bits to describe each pixel will produce perfect black and white photographs on its monitor.

30 A monitor that can show all these shades is called a greyscale display.

Now your eye can detect those 150-200 shades in all three of the colours it can see: red, green, and blue. If you use eight bits to describe colour, you only get 256 colours, which isn't enough – you get a mildly posterized effect, although the dithering process can

35 simulate more colours at the expense of quality.

To get the full colour photographic effect on a computer monitor, you need to be able to generate 256 shades for each colour. This takes eight bits of information per colour, giving a total of 24 bits. This is the 24-bit colour that you keep reading about in computer

40 magazines. If you take all the possible variations of 256 shades of three colours, you end up with a possible 16.7 million colour shades.

Some computers, such as the Macintosh, offer 32-bit colour:

the spare eight bits can be used to control transparent overlays of colour - you get 256 levels of transparency.

45 You only really need 24-bit colour if you are going to do colour photographic retouching on-screen or similar 'painting' on-screen. For linework and picture placing, an 8-bit colour monitor is perfectly adequate, as you can still define colours for print even if you can't show them on the screen.

50 Naturally, there's a bottom line in all this, or everyone would be using 24-bit colour. To start with, you need special circuit boards which plug into your computer and drive the monitor. An 8-bit board

is cheaper than a 32-bit one.

You also need plenty of memory. A typical high resolution

55. colour monitor can display about a million pixels. The 24 bite that your computer uses to describe each pixel can also be described as three bytes. To describe a million pixels takes three million bytes. In other words, a hefty three megabytes of your computer's memory is assigned to driving the screen. With 8-bit colour, you only need one

60 Mb.

Generally, 24-bit colour boards include extra memory and processors to speed up the display performance.

Your opinion: It's cheaper to be colour-­blind.