Delete Keys - Clipboard Technology

Oxford English for

Computing

Keith Boeckner

P. Charles Brown

Oxford University Press

Page Page

Unit 1 4 Unit 9 100

Personal computing 4 Computers in education 100

The processor 8 CALL 103

Language focus A11 Language focus I108

Contextual reference Giving examples

Unit 2 13 Unit 10 110

Portable computers 13 Computers in medicine 110

Operating systems 20 Data storage and management 115

Language focus B24 Language focus J120

Word formation prefixes Explanations and definitions

Unit 3 28 Unit 11123

Online services 28 Robotics 123

Data transmission 32 Robot characteristics 128

Language focus C36 Language focus K131

Word formation suffixes Compound nouns

Unit 4 39 Unit 12134

Programming and languages 39 Virtual reality 134

C language 44 VR input devices 139

Language focus D49 Language focus L142

Organizing information Classifying

Unit 5 52 Unit 13145

Computer software 52 Machine translation 145

Comparing software packages 57 Al and expert systems 148

Language focus E61 Language focus M152

Making comparisons Cause and effect

Unit 666 Unit 14155

Computer networks 66 Multimedia 155

Network configurations 70 Computer-to-video conversion 160

Language focus F75 Language focus N164

Time sequence Making predictions

Unit 778 Unit 15167

Computer viruses 78 Computer graphics 167

Computer security 81 24-bit colour 172

Language focus G86 Appendix 1176

Listing Letter writing

Unit 8 88 Appendix 2197

Computers in the office 88 Glossary of terms

Information systems 94

Language focus H97

The passive

Personal computing

Start-up

Listening

Interview 1 Interview 2

Name:

Occupation:

Type of PC used:

Reasons for choice: 1

3

Reading

Before reading the text on the following page, match each word with the correct definition:

the set of software that controls a computer system

a very small piece of silicon carrying a complex electrical circuit

a big computer system used for large-scale operations the physical portion of a computer system

a device moved by 'hand to indicate position on the screen

a visual symbol used in a menu instead of natural language

data, programs, etc., not forming part of a computer, but used when operating it.

Task 5 Now read the text and decide on a suitable title for it.

n 1952, a major computing company took a decision to get out of the business of making mainframe computers. They

5 believed that there was only a market for four mainframes in the whole world. That company was IBM. The following year they reversed their decision.

1() In 1980, IBM decided that there

was a market for 250,000 PCs, so they set up a special team to develop the first IBM PC. It went on sale in 1981 and set a world-wide

15 standard for IBM-compatibility which, over the next ten years, was only seriously challenged by one other company, Apple Computers. Since then, over seventy million

20 PCs made by IBM and other

manufacturers have been sold. Over this period, PCs have become commodity items. Since IBM made the design non-proprietary, anyone

25 can make them.

The history of the multi-billion dollar PC industry has been one of mistakes. Xerox Corporation funded the initial research on

30 personal computers in their Palo Alto laboratory in California. However, the company failed to capitalize on this work, and the ideas that they put together went

35 into the operating system developed for Apple's computers. This was a graphical interface: using a mouse, the user clicks on icons which represent the function

40 to be performed.

The first IBM PC was developed using existing available electrical components. With IBM's badge on the box it became the standard

45 machine for large corporations to purchase. When IBM were looking for an operating system, they went

initially to Digital Research, who were market leaders in command-

50 based operating systems (these are operating systems in which the users type in commands to perform a function). When the collaboration between IBM and Digital Research

55 failed, IBM turned to Bill Gates, then

25 years old, to write their operating system.

Bill Gates founded Microsoft
on the basis of the development

60 of MS/DOS, the initial operating system for the IBM PC. Digital Research have continued to develop their operating system, DR/DOS, and it is considered by

65 many people to be a better product than Microsoft's. However, without an endorsement from IBM, it has

become a minor player in the

70 market. Novell, the leaders in PC networking, now own Digital Research, so things may

change.

The original IBM PC had a

75 minimum of 16K of memory, but this could be upgraded to 512K if necessary, and ran with a processor speed of 4.77MHz. Ten

years later, in 1991, IBM were

so making PCs with 16Mb of memory, expandable to 64Mb, running with a processor speed of 33MHz. The cost of buying the hardware has come down

85 considerably as the machines have become commodity items. Large companies are

considering running major applications on PCs, something

90 which, ten years ago, no one would have believed possible of a PC. In contrast, many

computers in people's homes are just used to play computer 95 games.

The widespread availability of computers has in all probability changed the world for ever. The microchip technology which

loo made the PC possible has put chips not only into computers, but also into washing-machines and cars. Some books may never be published in paper form, but

105 may only be made available as
part of public databases.

Networks of computers are already being used to make information available on a world-

110 wide scale.

Vocabulary

commodity items (1. 2 3) — items which can be produced and traded freely non-proprietary (I. 24) — not belonging to any single company

capitalize on (I. 3 3) — profit from, turn to one's advantage

read the text slowly and try to understand every word?

Fl read quickly and try to understand the main theme?

underline or mark sentences that you thought were important? make notes about important points?

Which of these reading strategies do you think is most appropriate for this kind of task? Which do you think is least appropriate?

Task 7Answer these questions about the text.

1 How many mainframes did IBM think it was possible to sell in 1952?

2How many PCs have now been sold?

3Who paid for the initial research into PCs?

4Which company later used the results of this research to develop their operating system?

5What are command-based operating systems?

6DR/DOS is an acronym. What does it stand for?

7Since the invention of the IBM PC, many of its features have been improved. Which of the following features does the text not mention in this respect?

amemory

bspeed

csize

dcost

8Give three examples from the text of how the availability of computers has 'in all probability changed the world for ever'.

The processor

Reading

Read this passage about the structure of the processor and fill in the gaps using the words below.

has , which are electronic circuits providing specialized

functions such as graphics, or which connect a system board to

6 . The system board also consists of electronic devices, such

as an electronic for controlling the speed of operation;

8 , which store numeric data during the course of processing;

and various ⁹ _, including sequence control register, address
register, and function register.

adaptor boards registers microprocessor

clock conductive buses

system board accumulators input or output devices

Reading

Use the information in the reading passage and the diagram to help you match the terms below with the appropriate explanation or definition.

Aprocessor consists of many different electronic circuits and devices for performing control functions, arithmetic and logic operations, and data transfers. Data may be transferred from backing storage to the internal memory or from the internal memory to the arithmetic unit by means of

5 conductive channels known as buses. The part of the processor which controls data transfers between the various input and output devices is called the control unit.

Across

1A conductive line such as a data bus. (7)

2A visual symbol used in a menu to represent a file or program. (4)

3An input device used in computer games. (7)

4An device converts the electrical signals inside a computer into a form

that can exist outside the computer. (6)

SThe name given to system software that is held in ROM. (8)

6A device with one or more buttons used to point at locations on a computer screen. (5)

7The part of the CPU that transmits co-ordinating control signals and commands to the computer. (7,4)

81,048,576 bytes. (8)

9A large store of computerized data. (8)

10The system was first used commercially on the Apple Macintosh

computer, but is now widely used on IBM machines. (7)

11A signal route dedicated to sending information about locations within a computer. (7,3)

Down

12A register containing the results of an operation performed by the arithmetic-logic unit. (11)

Language focus A

Contextual reference

Transitional markers are words used to link ideas together so that the text is easier to read. When pronouns such as it, they, them, I, he, she, which, who, whose, that, such, one, and demonstrative adjectives such as this, that, these and those, are used as transitional markers, they refer to a word, or words, mentioned earlier in the sentence or paragraph. Their function is to take your thoughts back to something that has already been mentioned. Other words which are often used to refer backwards are the former, the latter, the first, second, etc., the last.

Using the sample paragraph as a model, draw a rectangle around the word, or words, that the circled words refer to. Then join the CD and the =with arrows.

Portable computers

`This is the smallest, most powerful computer in the world.'

`Those? Those are the batteries.'

Start-up

Task 1Discuss the following questions:

1 How small do you think computers can usefully become?

2 To what extent does the size of a computer influence what it can be used for? Think of examples to illustrate your answer.

Listening

Task 2Listen to the following extract from a radio talk show called Computerworks in

which the host talks with Sandra Cavanah, a writer with a computer magazine. As you listen, fill in the missing information about the various portable computers.

PortablePower: Weight: Screen size: Inplnputvice:

runs on between 15 and about ten inches diagonally keyboard

pounds

Notebook Power: batteries Weight: as little as Screen size: as small as _ Input device: keyboard

pounds inches

Reading

Task 3Before reading the text, match these words with their definitions:

aclipboard

bstylus

cscreen

dgrid

e voltage

fpixel

gtemplate

1 surface on which pictures or data are shown

2electrical force

3pattern used as a guide for creating letters or characters

4individual dot on a computer screen

5network of lines crossing at right angles

6pointed implement for drawing or writing

7portable board with a clip at the top for holding papers

Task 4Read the text and decide why the author chose the title Delete Keys. Can you

suggest a better title?

Delete Keys - Clipboard Technology

OR THE LAST GENERATION, Silicon Valley and Tokyo have

been working to design computers
that are ever easier to use. There is

5 one thing, however, that has prevented the machines from becoming their user-friendliest: you still have to input data with a keyboard, and that can require you

10 to do a lot of typing and to memorize a lot of elaborate commands.

Enter the clipboard computer, a technology that has been in

15 development for the last 20 years but took hold in the mass market only this year. Clipboard PCs —which, as their name suggests, are not much bigger than an actual

20 clipboard — replace the keyboard with a liquid crystal display (LCD) screen and an electronic stylus. Users input data by printing individual letters directly on the

25 screen.

There are two technologies at
work in a clipboard PC: one allows
raw data to get into the computer
and the other allows the computer

30 to figure out what that data means. The first technology relies principally on hardware and varies depending on the particular computer. In one system, marketed

35 under the name GRIDPad, the computer's LCD screen is covered by a sheet of glass with a transparent conductive coating. Voltage is sent

across the glass in horizontal and

40 vertical lines forming a fine grid; at any point on the grid, the voltage is slightly different. When the stylus — which is essentially a voltmeter — touches

45 the screen, it informs the

computer of the voltage at that point. The computer uses this information to determine where the stylus is and causes a liquid

so crystal pixel to appear at those

coordinates. The position of the stylus is monitored several hundred times a second, so as the stylus moves across the glass,

55 whole strings of pixels are activated.

`What we do is sort of connect

the dots,' says Jeff Hawkins, the creator of GRIDPad. 'Users can

60 then write whatever they want on the screen with a kind of electronic ink.'

Making that writing comprehensible to the computer,

65 however, requires the help of some powerful software. When the stylus is being used, the computer is programmed to look for moments when the tip does

70 not touch the screen for a third of a second or more. Every time this happens — and it happens a lot when somebody is printing —the software assumes that one

75 letter or number has been

written. The pixel positions of 1⁰.-

41 this fresh character are then passed on to the computer's pattern recognition software, which

so instantly identifies the letter or number written.

The software does this by first cleaning up the character —smoothing out crooked lines and

85 removing errant dots. The remaining lines and curves are then compared with a series of templates in the computer's memory that represent hundreds of thousands of

90 different versions of every letter in the English alphabet and all ten numerals. When the computer finds the closest match, it encodes the character in memory and displays it

95 on the screen as if it had been typed. The entire process takes just a fraction of a second. To delete a word, you simply draw a line through it. To move to the next

too page, you flick the stylus at the bottom of the screen as if you're flicking the page of a book.

There are a handful of clipboard

computers now on the market,

105 including GRIDPad, which is sold in the US; Penvision, manufactured by NCR and sold around the world;

and Sony's Palmtop and Canon's Al Note, both sold only in Japan.

1() IBM and Apple are also pouring millions of dollars into the technology.

In addition to this hardware, a variety of software is also

115 making its way to the market. Depending on the power of the computer and the sophistication of the software, clipboard

systems can be programmed to

120 understand the particular quirks of a particular user's printing; this is an especially useful

feature in Japan, where

elaborate kanji characters make

125 up most of the written language. Improvements in software may soon allow machines sold in the US to understand not only printing but continuous script as

130 well.

Given such flexibility, the designers of clipboard computers are predicting big things — and a big market — for their products.

135 'There's no doubt about it,' says an optimistic Hawkins. 'You're going to own one of these things in the not-too-distant future.' ■

Vocabulary

printing (1. 73) — (in this case) writing separated letters or numbers by hand kanji (1. 124) — Japanese script which uses Chinese characters

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

The Americans and the Japanese are working together to produce user-friendlier computers.

The clipboard computer was first sold twenty years ago.

On a clipboard, an electronic pen replaces the traditional keyboard.

ln the GRlDPad system, when the pen touches the screen, it informs the computer and a liquid crystal pixel appears at that point.

The software decides that one character or number is complete if the tip of the stylus is not in contact with the screen for more than half a second. The whole process of recognizing letters or numbers and printing them on the screen takes very little time.

There are many clipboard computers sold today which are all available everywhere in the world.

Clipboard systems can be made to understand any kind of writing.

1 electron, electronic, electronics, electronically

aAn pen is one example of an input device.

bA computer solves problems

c Many _______ students go on to work as engineers.

2technology, technological, technologically, technologist

aThe computer is the greatest ___________ invention of the twentieth

century.

bThere are two ________ involved in a clipboard PC.

c Today's computers are far superior to those used a few years ago.

3 identify, identifying, identifiable, identity

aThe clipboard's pattern recognition software immediately the letters and numbers written by the stylus.

bMost computer companies will not allow people without an card to enter their premises.

cA password is a mechanism for____________ the computer-user and

allowing access.

4compute, computing, computation, computerize, computerization

aThe of the manufacturing division will be expensive in the

short term, but cost-effective in the long term.

Speaking

Task 11Discuss the following questions:

1 What are the limitations of portable computers?

2Do you think students should be allowed to use portable computers in class?

Writing

Write an advertisement for a real or imaginary notebook computer. Your material should include its name and type, its size, price, and capacity, and the features that make it superior to other models.

You may base your material on the advertisement above, but do not copy straight from the text.

Speaking

Task 13Work in pairs.

Student A:You are a sales representative trying to sell your company's notebook computer. You are presenting your product to the Sales Director of a manufacturing company which is thinking of buying 30 notebook computers for the sales staff. Decide on the specifications and complete the table below. Then try to persuade the Sales Director to buy your product.

Name

Type (size)

Processor type Operating speed Memory

Display

Power supply Cost

Other features

4 Useful expressions It costs...

It runs/operates on... It weighs...

Student B:You are the Sales Director of a manufacturing company. You are considering buying 30 notebook computers for your sales staff. Find out about all the specifications of the model on offer. Decide whether it is suitable for your needs.

4 Useful expressions

How much does it cost?

What power source does it use? How big/heavy is it?

Operating systems

Reading

Task 14Before you read the text, try to answer the following questions:

1What is an operating system and what is its purpose?

2Where is an operating system stored and how is it transferred to internal memory?

3List some of the tasks typically performed by an operating system.

Now read the text and check your answers.

General features of operating systems

An operating system is a master control program which controls the functions of the computer system as a whole and the running of

application programs. All computers do not use the same operating systems. It is therefore important to assess the operating system used on a

5 particular model before initial commitment because some software is only

designed to run under the control of specific operating systems. Some operating systems are adopted as 'industry standards' and these are the ones which should be evaluated because they normally have a good software base. The reason for this is that software houses are willing to

1() expand resources on the development of application packages for machines functioning under the control of an operating system which is widely used. The cost of software is likely to be lower in such circumstances as the development costs are spread over a greater number of users, both actual and potential.

15 Mainframe computers usually process several application programs concurrently, switching from one to the other, for the purpose of increasing processing productivity. This is known as multiprogramming (multi-tasking in the context of microcomputers), which requires a powerful operating system incorporating work scheduling facilities to

20 control the switching between programs. This entails reading in data for one program while the processor is performing computations on another and printing out results on yet another.

In multi-user environments an operating system is required to control terminal operations on a shared access basis as only one user can access

25 the system at any moment of time. The operating system allocates control
to each terminal in turn. Such systems also require a system for record
locking and unlocking, to prevent one user attempting to read a record
whilst another user is updating it, for instance. The first user is allocated
control to write to a record (or file in some instances) and other users are

30 denied access until the record is updated and unlocked.

Some environments operate in concurrent batch and real-time mode. This means that a 'background' job deals with routine batch processing whilst the 'foreground' job deals with real-time operations such as airline seat reservations, on-line booking of hotel accommodation, or control of

35 warehouse stocks, etc. The real-time operation has priority, and the operating system interrupts batch processing operations to deal with real-time enquiries or file updates. The stage of batch processing attained at the time of the interrupt is temporarily transferred to backing storage. After the real-time operation has been dealt with, the interrupted program is

40 transferred back to internal memory from backing storage, and processing recommences from a 'restart' point. The operating system also copies to disk backing storage the state of the real-time system every few minutes (periodic check points) to provide a means of 'recovering' the system in the event of a malfunction.

45 An operating system is stored on disk and has to be booted into the internal memory (RAM) where it must reside throughout processing so that commands are instantly available. The operating system commands may exceed the internal memory capacity of the computer in which case only that portion of the OS which is frequently used is retained internally,

50 other modules being read in from disk as required. Many microcomputers
function under the control of a disk operating system known as DOS.

searches for a specific string of text in a file. allows a text file from the current directory to be displayed on screen.

allows the user to change the name of a file.

saves the contents of the hard disk to a floppy disk for security purposes.

is used when it is necessary to change the current directory.

clears data from the screen.

alphabetically sors and lists a disk directory. makes back-up copies of the contents of one disk to another.

deletes a specified file from the current directory, specified drive, or specified path.

produces a status report of the currently logged-on disk, indicating the amount of disk space used, the available capacity (in bytes), and the number of files on disk.

Find words which mean:

1 a computer that is small enough to hold in the hand. (7, P)

2an electronic pen. (6, S)

3to erase or omit. (6, D)

4one type of portable computer which operates with an electronic pen. (9, C)

5the information that the computer processes. (4, D)

6a network of lines crossing at right angles. (4, G)

7 a signal to a processor to suspend temporarily the current sequence of instructions. (9, I)

8a pattern used as a guide for creating letters or characters. (8, T)

9an individual dot on a computer screen. (5, P)

Language focus B

Word formation: prefixes

When you are reading, you will come across unfamiliar words. lt is often possible to guess the meanings of these words if you understand the way words in English are generally formed.

An English word can be divided into three parts: a prefix, a stem, and a suffix. Pre-means 'before'. A prefix, therefore, is what comes before the stem. Consider, as an example, the prefix de- (meaning 'reduce' or 'reverse') in a word like demagnetize (meaning 'to deprive of magnetism'). A suffix is what is attached to the end of the stem. Consider, as an example, the suffix -er (meaning `someone who') in programmer Ca person who programs').

Suffixes change the word from one part of speech to another. For example, -ly added to the adjective quick gives the adverb quickly. Prefixes, on the other hand, usually change the meaning of the word. For example, un- changes a word to the negative. Unmagnetizable means 'not capable of being magnetized'.

Let us now consider some prefixes, their usual meanings, and how they change the meanings of English words.

Exercise 1Study these tables. Try to find additional examples, using your dictionary if

necessary.

1 Negative and positive prefixes:

semi- half, partly semiconductor

equi- equal equidistant

mini- small minicomputer

micro- very small microcomputer

^macro-large, great 1 macroeconomics

mega- megabyte

semi- half semicircle

mono- one monochromatic

bi- two binary

tri- three triangle

quad- four quadruple

penta- five pentagon

hex- six hexadecimal

sept(em)- seven September

oct- eight octal

dec- ten decimal

multi- many multiplexor

7Peripheral devices can be either input devices (such as keyboards) or output devices (such as printers).

8Your pay rise is retroactive to the beginning of June and you will receive a bi­annual bonus.

9The octal and hexadecimal systems are number systems used as a form of shorthand in reading groups of four binary digits.

10 As the results are irregular, the program will have to be rewritten.

Exercise 3Fill in the gaps with the correct prefix from the following list.

auto de dec inter

maxi mega micro mini

mono multi semi sub

1 Most people prefer a colour screen to a______ chrome screen.

2_script is a character or symbol written below and to the right of a
number or letter, often used in science.

3A ____ byte equals approximately one million bytes.

4Once you finish your program, you will have to test it and______ bug it to
remove all the mistakes.

5The introduction of _____ conductor technology revolutionized the computer

industry.

6If a computer system has two or more central processors which are under common control, it is called a___________ processor system.

7The imal system is a number system with a base of 10.

8When the user and the computer are in active communication on a graphics system, we refer to this as_________________ active graphics.

Online services

Task 1Discuss the following questions:

1What online services are available in your country?

2What kind of facilities do online services provide?

Most people choose an online service because of the price or the number of available files.

Everybody has one service which he/she likes more than all the others. You should judge each BlX.ice according to whether it is better or wBlXe overall than the service you are currently using.

Eventually, all services will be accessible from the service you are using.

McGraw-Hill is owned byDELPHl'S

Tammy Ray and Jeanette Shearer think the BIX service is average. French Minitel users have free access to an English-language version of CompuServe, although they cannot use the e-mail facility.

DELPHI'S Hobby Shop now has two special-interest areas: onlfon classic vehicles, and one on new cars and technology.

Online Services

I'm frequently asked which online service is 'best', but the answer is there is no best. Rating a particular service over another is entirely

5 subjective. Price is important to some people, while the number of files available for download is important to others. Because of these and so many other different judgments, there can be

10 no absolute. It all comes down to individual needs and preferences.

Still, users tend to be fiercely loyal to their 'home' online service-which is usually the first online service they

15 ever used. They tend to judge all other online services based on this first service - often preventing themselves from seeing the advantages of a specific service. For my part, I like all

20 the services I use and I'm on two dozen.

Each offers one or more products or features that either do not exist elsewhere or are superior to the same

25 features on other services. And I've a really subjective reason for being on one service - I use it to send monthly articles to magazines in Japan.

So, the real answer to the question

30 is simple: the best online service is the service that has what you want and is easy for you to use. The point? Keep an open mind when checking out an online service. Judge it based on what

35 it offers and how it meets your needs -not in comparison to what you're used to using. (It takes a couple of sessions to shake preconceived notions of what an online service 'should' be.)

ao 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'.

Until then, most of us have to go

45 to more than one service to find everything we need.

And now, the news ...

IN. Vocabulary

It all comes down to (1. 10) — It is a question of two dozen (1. 20) — about twenty-four checking out (1. 33) — examining

is moderated by (1. 58) — is run by

bolstered (1. 68) — strengthened

Task 3Fill in the gaps in this summary of the first part of the text. Each clue is an

anagram. The first and last letters are correct.

In my opinion, there is no single 'best' online service. The choice depends on
your (prltacuair) needs and preferences. Most users have their

own ²_____________ (ftrvaioue), but this can prevent them from seeing the

________ (agtvndaaes) of other services. Each one offers something which

is either ⁴ (uqinue) to that service, or which is ⁵

(bteetr) than the same features on other services. So, when considering an

online service, decide whether its features ⁶_ (cosrernopd) to what

you need. Until all services are^' (iilktneernd), most of us will need

to___________ (cunoitne) using more than one.

Task 4 1Do you think the English in the text is:

aformal?

bneutral?

cinformal?

2Do you think this article originally appeared in:

aa computer magazine?

ba general magazine for young people?

ca general magazine for adults?

dan online bulletin board?

ethe science page of a newspaper?

Give reasons for your choices.

Task 5Make these words negative by adding the appropriate prefix from those given

below. The first one has been done for you.

in- un- im- dis-

1 infrequently

2loyal

3 ______advantages

4specific

5 ______like

6real

7probably

8available

Task 6Match each word or expression in the first column with a synonym in the

second column.

1 but (line 2) aultimately

2while (line 6) bhowever

3still (line 12) cwhereas

4for my part (line 19) dnevertheless

5eventually (line 40) epersonally

6until then (line 44) fmeanwhile

Listening

Task 7 riListen to Jean-Yves Martin, a sales representative of France Telecom,

explaining the Minitel online service to Paul Burgess, an English reporter. Complete Paul's notes.

Task 8 rAnswer these questions about the interview.

1What is 'Minitel rose'?

2 When did the system start?

3 How many Minitel terminals did the PTT install originally?

4 Did the first users have to pay?

Data transmission

Reading

Match up the jigsaw pieces to complete the definitions. One has been done for

Task 10Using the completed definitions from Task 9 and the information in the text

below, fill in the gaps in this diagram.

Accounts

Reading

Task 11Before reading the text below, answer these questions.

1 What are the advantages of digital transmission?

2 How does digital transmission differ from analog transmission?

3 What information does the code supply?

Now read the text to check your answers.

Digital transmission

Analog transmission has been in use for many years as the basis of telephone technology and is very effective for this purpose, but it is not so suitable for high-speed transmission of information. Digital transmission consists of electrical pulses representing data in binary code as a series of

5 on/off pulses. A number of different codes exist, some of which are based on a 6-, 7-, or 8-bit structure. ASCII is a 7-bit code and EBCDIC is an 8-bit code. The codes represent characters, transmission control signals, information separators, and device control. Digital technology has a number of advantages compared to analog, including higher transmission

1() speed, lower incidence of errors, and the facility for mixing data consisting of voice, image, and text on the same circuit. It is for this reason that data transmissions will be increasingly digital in the future. A network structure known as Integrated Services Digital Network (ISDN) facilitates these aspects.

Speaking

Task 12Work in pairs, A and B. Use the information in this unit to describe the

diagrams below. You may make notes first.

Student A: Describe diagram 1 to your partner.

AC — Acoustic coupler CC — Cluster controller M — Modem

MP — Multiplexor

PC — Personal computer T — Terminal

Writing

Task 13Write a paragraph to show the difference between analog and digital

transmission.

Across

1A combination of electronic devices and conductors that form a conducting path. (7)

2 An agreement that covers the procedures used to exchange information between co-operating computers. (8)

3This kind of transmission has been the basis for telephone technology for many years, though it is gradually being replaced. (6)

4 To send programs or data from a central computer to a remote PC. (8)

5Single vibrations of electric current. (7)

6A VDU screen and keyboard used to interact with a computer, usually with no computing capacity of its own. (8)

7This kind of transmission consists of electrical signals representing data in binary code. (7)

8A public database, for example, that can be accessed over a computer or telephone network. (6, 7)

9A____ controller controls a number of similar peripheral device such as

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