Impact printers by mechanical contact between print head and

paper. On the other hand, non-impact printers do not require mec-

hanical contact. Impact printers are noisy, whereas non-impact

printers are silent.

- 29 -

Finally, we can add examples.

The daisywheel printer is an example of impact printer. One

type of non-impact printer is a thermal printer.

Task 7

Another way to classify printers is by speed.

Study these facts about fast and slow printers.

ЪДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДї

і Fast і Slow і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і usually print a line or і print a character at a time і

і even a page at a time (line) і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і used with mainframe computers(line)і used with microcomputers і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і very expensive (line) і inexpensive і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і e.g. laser і e.g. daisywheel і

АДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЩ

Now complete the blanks in this paragraph.

Printers can also be ............. into ............ and

slow printers. Fast printers ..........................., whereas

.......................... print a character at a time. Fast

printers are normally used with mainframe. On the other hand

............................... with microcomputers. Fast prin-

ters are ............, whereas ............... relatively inex-

pensive. One type of fast printer .............................. .

The daisywheel printer ....................................... .

Task 8

Study these facts about plotters which are used for printing

- 30 -

high-quality, detailed graphics such as are required in Computer

Aided Design. Use these facts to write your own paragraph.

It should include: a classifying sentence

a comparison and contrast of several points

ЪДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДї

і Plotters і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і drum plotters і flatbed plotters і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

іpaper is placed over a drum і paper is placed over a bed і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

іthe drum and pen movements і only the pen is moved to produceі

іare used to produce the drawing the drawing і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

іthe drawing is produce in іthe drawing is produce in a і

іseries of small steps іseries of small steps і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

іslow іslow і

АДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЩ

.

- 31 -

UNIT FIVE

D A T A C O M M U N I C A T I O N S

Task 1

Try to answer these questions.

1. What is the purpose of a graphics terminal ?

2. How can terminals be connected to a computer which is a long

distance away ?

Now read the Text quickly to check your answers or find the

correct answers.

A multi-user system is made up of a number of terminals sha-

ring a mainframe computer. Each terminal consists of a least one

input device and output device and allows the user to communicate

with the computer.

There are a number of different types of terminals. For

example, a teletype terminal is made up of a keyboard and a prin-

ter which gives a hardcopy output.

A VDU terminal has a keyboard and a VDU screen. It usually

has its own internal processor which deals with input/output and

editing of data and is, therefore, referred to as an intelligent

terminal.

A graphics terminal is similar to a VDU terminal but is spe-

cially designed to display graphics such as pictures, maps,

graphs, diagrams etc. and has a lightpen attached to allow the

user to `draw` on the screen. It is normally used for Computer

3131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131 known as a data communications (or

datacomm) system.

Task 2

Read the Text again to complete this table.

ЪДДДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДї

і Terminal і Components і Features і

ГДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДґ

і 1 Teletype і і і

ГДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДґ

і 2 VDU і і і

ГДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДґ

і 3 Graphics і і і

АДДДДДДДДДДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДЩ

Task 3

Now work in pairs, A and B. If working alone, do both parts.

Read the Text below to find out the functions of each of these:

Student A Student B

1 network 1 network

2 LAN 2 WAN

3 modem 3 fibre optics cable

4 communications satellite 4 microwave radio

Note your findings in the Table.

When you have completed your section of the table, share

your findings with your partner so that can both complete the

table.

- 33 -

ЪДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДї

і Datacomm Systems і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і Component і Function і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 1 Network і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 2 LAN і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 3 WAN і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 4 Modem і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 5 Fibre optics cable і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 6 Microwave radio і і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 7 Communications satelliteі і

АДДДДДДДДДДДДДДДДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЩ

Datacomm systems may also be formed from a number of compu-

ters and peripherals connected together in a network. This allows

software and hardware to be shared by a large number of users

over long distances.

A network which is contained in a relatively small area,

such as an office building, factory site or university campus, is

known as a Local Area Network or LAN. The two main types of LAN

are single cable networks and loop networks.

In a single cable network, each computer `listens` all the

time for data addressed to it and only transmits data when the

network is quiet. A loop network, on the other hand, continuously

circulates data `slots` which can be filled with data. Data is

transmitted by filling an empty slot with a `packet` of data as

the slot passes the transmitting device.

If the network is connected over a larger area it is called

- 34 -

a Wide Area Network or WAN. This may be linked using telephone

lines. Dedicated lines are permanently connected to a system but

dialled lines are only connected when needed. However, existing

telephone lines are designed to carry analogue signals and not

the digital signals used by computers. A special device is there-

fore needed at each end of the telephone line to convert the sig-

nals to the correct form. This device is known as a modulator/de-

modulator or modem. A special kind of modem known as an acoustic

coupler has rubber cups into which an ordinary telephone can be

plugged.

Although this avoids having to make a special connection in-

to the telephone system, it is more likely to suffer from corrup-

tion of data due to interference.

Modern telecommunications systems are being developed using

fibre optics cables. These allow data to be transmitted as pulses

of light along thin strands of glass (about the thickness of a

human hair). In this way, data can be communicated at very low

levels of interference. When telecommunications systems have been

converted to digital systems using fibre optics cables and elect-

ronic telephone exchanges, modems will no longer be required.

Data can be communicated over long distances and over water

by using microwave radio links. These transmit and receive high

frequency microwave signals using small dish aerials. Since there

must be a clear path between these aerials, they are usually si-

tuated at the top of high towers.

Data communications over very long distances can make use of

communications satellites which are placed in fixed orbits above

the Earth. The satellites receive signals from ground stations on

Earth, amplify the signals, then re-transmit them to other ground

stations which may be in another country or another continent.

The development of efficient data communications systems is

an important aspect of the growth in information technology.

- 35 -

Study these details about different types of terminals.

ЪДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДДДДДДВДДДДДДДДДДДДДДДДДДДДДДДї

іTerminal і Components і Features і

ГДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДґ

іTeletype і keyboard, printer і hardcopy output і

ГДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДґ

іVDU і keyboard, internal і allows data to be і

і і processor, VDU screen і edited easily і

ГДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДДДЕДДДДДДДДДДДДДДДДДДДДДДДґ

іGraphics і keyboard, internal іused for Computer і

і і processor, VDU screen, іAided Design і

і і lightpen і і

АДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДДДДДДБДДДДДДДДДДДДДДДДДДДДДДДЩ

We can compare things which are similar as follows:

1. A VDU terminal is similar to a graphics terminal.

2. Both the VDU and the graphics terminal have VDU screen.

3. Like the teletype terminal, the VDU terminal has a keyboard.

We can contrast things which are different as follow:

4. A graphics terminal is different from a teletype terminal.

5. A teletype terminal can produce hardcopy output, whereas a

graphics terminal is designed to display diagrams, etc. on a

VDU screen.

6. Unlike a teletype terminal, a VDU terminal usually has an in-

ternal processor.

7. In contrast to ordinary terminals, intelligent terminals have

their own internal processor.

Task 4

With the help of both Texts and Glossary, write a sentence

of comparison and contrast for each of these.

1. Dedicated lines, Dialled lines

2. Analoque signals, Digital signals

3. Local Area Networks, Wide Area Networks

- 36 -

4. Ordinary telephone cables, Satellite links

5. Microwave radio, Output devices

6. Input devices, Output devices

7. Impact printers, Non-impact printers

8. Microcomputers, Mainframe computers

Task 5

Two important types of data communications services are

known as message switching services and videotex services.

Read the text to note three types of message switching ser-

vices and two types of videotex services. Write your answers in

the Table.

ЪДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДї

і Message Switching і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 1 і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 2 і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 3 і

АДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЩ

ЪДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДї

і Videotex і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 4 і

ГДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДґ

і 5 і

АДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДЩ

Task 6

Read the text again. Which form of data communications would

be used for each of these needs ?

1. To send a copy of a contract from one office to another.

2. To make travel information available to TV viewers in their

- 37 -

own homes.

3. To send an equiry quickly to an overseas company.

4. To send a photographic image from one police station to anot-

her.

5. To transfer money from one account to another from one`s home.

6. To find out weather information before going on a journey.

7. To store messages from different sources for later collection.

8. To send copy from one newspaper printers to another in a form

ready for printing.

9. To order and to pay for goods from one`s home.

Task 7

Study these definitions of different terms. Then complete

the term defined with the correct word, tele, data, or video.

1. Pages of text broadcast as part of a TV signal. ........text

2. A kind of storage device written to and read from by a laser

beam. ........disc

3. A large collection of information which can be searched to

find a particular item. ........base

4. A device that can send and receive data over long distances

and produce a hardcopy printout. ..........printer

5. A form of data communications service which allows large amo-

unts of information to be displayed on TV screens. .....tex

6. The transfer of information over long distances using telepho-

ne lines, satellites, microwaves radio, etc. ...communications

7. A kind of terminal consisting of a keyboard and a printer,

used for sending message over distances. ......type terminal

8. A system for the transfer of information, formed by a computer

and terminals connected by telecommunications links.

.............. communications system

9. A system using teleprinters and telephone system to provide

information exchange all round the world. ..........x

.

- 38 -

UNIT SIX

S O F T W A R E S Y S T E M

Task 1

Try to answer these questions.

1 What is a program library?

2 What is a payroll program for?

Read the text quickly to check your answer or to find the

correct answers.

The information used with computers is known as software and

includes programs and data. Programs are sets of instructions

telling the computer what operations have to be carried out and

in what order they should be done.

Specialised programs which enable the computer to be used

for particular purposes are called applications programs. A col-

lection of these programs kept in backing store,form what is

known as a program library.

There are two different types of applications programs;name-

ly custom programs and applications packages.

Custom programs are designed to suit a particular situation

and are usually written by the user himself. Applications packa-

ges,however,are more general and are purchased complete with ex-

tensive documentation explaining how to use them for particular

purposes. Common applications packages include payroll programs

for calculating employees' wages ,database programs for informa-

tion retrieval,word processor programs for text manipulation and

spreadsheet programs for financial planning.

Integrated packages have a number of programs combined in

one package so that the same data can be shared by them all.

Applications programs are usually stored on disc and loaded

into the main memory when required. However,they can also be put

onto ROM chips to make them immediately available to the user.

- 39 -

Task 2

Read the text again to complete this diagram.

Software

і

ЪДДДДДДБДДДДДДДДДї

Programs ЪДДДДДБДДДДДї

і і1 і

ЪДДДДДДДДДДДДДДДАДДДДДДДї АДДДДДДДДДДДЩ

ЪДДДДДДДДБДДДДДДї System

і2 і Programs

АДДДДДДДДВДДДДДДЩ

ЪДДДДДДДДБДДДДДДДДДДДДДДДДДДї

Custom ЪДДДДДДДБДДДДДДї

Programs і3 і

АДДДДДДДВДДДДДДЩ

e.g.Payroll Programs

і ДДДї

ЪДДДДДДДБДДДДДДї і

і4 і і

АДДДДДДДВДДДДДДЩ ГДДДIntegrated

ЪДДДДДДДБДДДДДДї і Package

і5 і і

АДДДДДДДДДДДДДДЩ і

ДДДЩ

Task 3

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

Student A Student B

Read the below Text to find Read the below Text to find

out about these types of out about these types of

systems programs: systems programs:

1 operating system 1 utility programs

2 database management 2 language translators

When you have completed your notes,share your information

- 40 -

with your partner.

SISTEMS PROGRAMS

OPERATING SYSTEMS LANGUAGE TRANSLATORS

main function________________ function ___________________

_____________________________ ____________________________

examples of functions________ examples____________________

_____________________________ ____________________________

_____________________________ ____________________________

UTILITY PROGRAMS DATABASE MANAGEMENT SYSTEMS

function ____________________ function __________________

_____________________________ ____________________________

examples_____________________ ___________________________

____________________________ ___________________________

The programs which control the basic functions of a computer

system are known as systems programs. They include the operating

system,utility (or service) programs, language translators and

database management systems.

The operating system is the most important type of systems

software. It consists of a group of programs designed to manage

and co-ordinate all the hardware and software of a computer sys-

tem as efficiently as possible and to provide communications bet-

ween the computer and the user. It is a very complex piece of

software which performs many different functions such as control-

ling the operation of the disc drives,displaying prompts and cur-

sors,keeping the system running if an error occurs in a prog-

ram,checking the input of identification numbers and passwords

and keeping a log of terminals used in a multi-user system.

The operating system must be compatible with the central

processor and is usually supplied by the computer manufacturer.