If the computer divides the screen into a large number of

small pixels, a very detailed, high resolution display is produ-

ced. This is suitable for displaying text and high quality grap-

hics but uses up a lot of the computer`s memory.

On the other hand, if the computer divides the screen into a

smaller number of large pixels, a less detailed, low resolution

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display is produced.

This is adequate for text and crude graphics and uses up

less of the computer`s memory.

The resolution of the display can be changing the screen mo-

de of the computer.

Task 2

Work in pairs, A and B. If working alone, do both tasks.

Read the Text bellow quickly to find out what kind of printer

each of the following is:

Student A Student B

1. daisywheel 1. dot-matrix

2. ink-jet 2. laser

3. line 3. thermal

The Table classifies printers. Write each of these printers in

the correct section of the table.

Now exchange information with your partner, to complete your table

Another common output device is a printer. This gives a

hardcopy printout i.e. computer output is printed on paper.

There are many different types of printers. To decide which

one is most suitable for a particular application, factors such

as cost, speed, noise output and print quality have to be taken

into consideration.

Impact printers print by forcing a print head into contact

with an inked ribbon and paper.

One common type of impact printer is a daisywheel printer.

This has solid characters positioned around a wheel. The wheel is

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rotated to the correct position and the required character is

hammered against the ribbon and paper. This type of printer can-

not print graphics and is very slow, having a maximum print rate

of about 60 characters per second (60 cps). However the quality

of print is very good. It produces what is referred to as Letter

Quality (LQ) print.

Another common type of impact printer is a dot-matrix prin-

ter. This uses pins to print a pattern of dots in the shape of

the required character. It can print text and graphics at rates

up to about 200 cps. However, the quality of the print is not as

good. The best print that can be achieved with this type of prin-

ter is known as Near Letter Quality (NLQ) print.

Although these types of printers are inexpensive, they can

be quite noise. Non-impact printers, on the other hand, give al-

most silent printing by using methods that do not require mecha-

nical contact between the print head and the paper e.g. heat,

electrostatic and lasers.

A thermal printer is an example of an inexpensive non-impact

printer. It uses heated wires to print characters on special heat

sensitive paper and can have a print rate of about 80 cps. Howe-