Network configurations

Reading

Read the following texts. Match each text with the correct illustration.
a b

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File server

(t

File server

Star

In the star configuration, the central computer performs all processing and control functions. All access devices are linked directly to the central computer. The star configuration has two major limitations. First of all, the remote devices are unable to communicate directly. Instead, they must communicate via the central computer only. Secondly, the star network is very susceptible to failure, either in the central computer or the transmission links.

Switched

The central switch, which could be a telephone exchange, is used to connect different devices on the network directly. Once the link is established, the two devices communicate as though they were directly linked without interference from any other device. At the end of the session, the connection is closed, freeing capacity for other users and allowing access to other devices. Multiple switches can be used to create alternative transmission routes.

Ring

Each device is attached to a network shaped as a continuous loop. Data proceeds in only one direction and at a constant speed round the loop. Devices may send information only when they are in control of the 'token'. The token is a package of data which indicates which device has control. The receiving device picks up the token, then clears it for another's use once it has received the message. Only one device may send data at any given moment, and each device must be working for the network to function.

Bus/Ethernet

A bus network consists of one piece of cable terminated at each end to which all devices are connected. In a bus-based network, each device is able to broadcast a message when it has detected silence for a fixed period of time. All devices receive the broadcast and determine from the content of the message whether it was intended for them. The only problem occurs when two devices try to send at the same time. When a sending device detects another's transmission, it aborts its own.

Task 11 These are answers to questions about the texts. Write the questions.

1 To connect different devices on the network directly.

2 No, it goes in only one direction round the loop.

3 No, only one device may send data at any given moment.

4 From the content of the message.

5 It cancels its own transmission.

Task 12 Which of the network configurations on page 71 does this flowchart refer to?

Task 13

The columns below describe characteristics of the bus and ring configurations. Which column refers to which configuration? How did you decide?

varied time response

easy expansion

fault-tolerant

simple

calculable time response

fault-intolerant more complex

Task 14

Speaking

Work in pairs, A and B, using the information in the advertisement opposite. Prepare the role-play in advance and try not to refer to the advertisement during the activity.

Student A: You are a customer interested in the Netplan Eazy Kit. Before deciding whether to buy it, ask questions to find out:

1 what you need in order to use the Netplan Eazy Kit.

2 the total number of PCs you can run on it.

3 the cost of adding additional PCs.

4 how difficult it is to install.

5 what software it runs.

6 the other features offered.

Student B: You represent the makers of the Netplan Eazy Kit. Make notes about the features of the product. Answer any questions and try to encourage the customer to buy it.

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This is not the only way to share software.

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Extra efficiency

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Task 15

Word-play

Solve the crossword puzzle using the clues below.

7 9

2 3 4 6 8

Across

The means of communication between a human and a computer. (4,9)

To load software on to a computer, ready for use. (7) To transmit a message to all nodes on a network. (9) and 3 down Usually found in one building or a group of buildings close

together. (5,4,7)

This kind of network often uses a telephone exchange to connect different

devices directly. (8)

Down

Taking place at exactly the same time as something else. (11)

See 9 across.

An_____ board may be inserted into a computer to give it added features. (9)

The opposite of 9 across and 3 down. (3)

The network configuration in which all devices are linked through the central

computer. (4)

Language focus F

Time sequence

In activities such as scheduling, doing routine activities, and conducting and describing experiments, it is important to recognize the sequence of events. As we know, events do not simply occur in isolation, they occur either before, during, or after other events. This time sequence may be chronological, logical, or causal. The following tables show examples of time relaters.

1 Before given time-references:

Examples:

1 The memory storage capacity of earlier computers was not as large as those
of today.

2 When the first digital computer was developed, the first analog computer had
already been in use for some time.

3 Up to now, voice recognition technology has not been developed for mass
marketing.

2 Simultaneous with given time-references:

Time relaters

Adjectives Adverbials

contemporary

at present

at this point

now/then

today

for the time being

at the moment

at that time

simultaneous

meantime

meanwhile

in the meantime

when

at the same time

75

Examples:

1 At that time many new computer programs were being developed for use in
businesses.

2 Computers may soon take over many daily tasks, but in the meantime
ordinary people must continue to do them themselves.

3 Computer magazines keep us informed about contemporary issues in the
computing world.

3 After given time-references:

Time relaters

Adjectives following later next

Adverbials afterwards since by the end

after that by the time soon

eventually next

Examples:

1 Since the development of the chip, computers have become cheaper and more
compact.

2 You should have a good idea of the various applications of computer software
by the time you finish reading this book.

3 Although initial versions of word-processing programs were not very
complex, later versions were much more sophisticated.

Sample paragraph:

Computers, as we know them today, have not been around for a long time. It was not until the mid-1940s that the first working digital computer was completed. But since then, computers have evolved tremendously. Vacuum tubes were used in the first-generation computers only to be replaced by transistors in the second-generation computers at the beginning of the earlyl960s. By the end of the 1960s, transistors themselves were replaced by tiny integrated circuit boards and, consequently, a new generation of computers was on the market. Fourth-generation computers are now produced with circuits that are much smaller than before and can fit on a single chip. Even now, new technologies are being developed to make even better machines.

Exercise 1 Read the following paragraph and, as you read, underline the time relaters.

During the seventeenth and eighteenth centuries, many easy ways of
calculating were devised. Logarithm tables, calculus, and the basis for the
modern slide rule were invented during this period. It was not until the early
1800s that the first calculating machine appeared and, not too long after,
Charles Babbage designed a machine which became the basis for building
today's computers. A hundred years later, the first analog computer was built,
but the first digital computer was not completed until 1944. Since then,
computers have gone through four generations: digital computers using
vacuum tubes in the 1 950s. transistors in the early 1960s, integrated circuits
in the mid-60s, and a single chip in the 1970s. In the 1980s, we saw
computers become smaller, faster, and cheaper. Earlier this decade, computers
became portable, fr-,^ Hntnoe tp n"ln'!nm 4* the* vMe computer technology is
growing now, we., \ ■ " ■.■,•; •■r-.i-.i.ni:. bclv ■-. _s.■••■■■ •

the century.

Exercise 2

Exercise 3

Read the following sentences which come from previous units. Underline the
time relaters and indicate whether they refer to before, during, or after the
given time reference. The first one has been done for you.
after Since then, over seventy million PCs made by IBM and other

manufacturers have been sold. (Unit 1)

________ Over this period, PCs have become commodity items. Since IBM

made the design non-proprietary, anyone can make them. (Unit 1)

___ _.-..... Ten years later, in 1991, IBM were making PCs with 1 6Mb of

memory, expandable to 64Mb, running with a processor speed of 3 3MHz. (Unit 1)

_________ - Large companies are considering running major applications on

PCs, something which, ten years ago, no one would have believed possible of a PC. (Unit 1)

___________ When the computer finds the closest match, it encodes the

character in memory and displays it on the screen as if it has been typed. (Unit 2)

___________ Enter the clipboard computer, a technology that has been in

development for the last 20 years but took hold in the mass market only this year. (Unit 2)

___________ Eventually, we're all going to be interlinked, no matter which

service we use, in what DIALOG'S Richard Ream calls a 'network of networks'. (Unit 3)

___________ Until then, most of us have to go to more than one service to

find everything we need. (Unit 3)

Now refer back to paragraphs 1,2,4, and 5 of the texf entitled Computer networks (page 67, Unit 6). Underline all the time relaters and indicate whether they refer to before, during, or after the given time reference.

I

Taski

Task 2

Before reading the text, match the words and definitions listed below.

a protective device

to remove all traces of something

a device used to set off an explosion or other destructive

process

to discover or recognize that something is present

to set a process in motion

something which transmits a disease or virus

stolen, obtained without the owner's consent

to load the operating system into memory

7cS

Task 3

Now read the text to check your answers to Task 1.

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