4T then works as a modem.

V x -an analog sighafover "

\ an analog /

J ^communication I

" ^y Channel (telephone V i

circuit).

It may act as a translator between incompatible

multiple signals from various terminals and ^N combines them in data / frames for transmission I on a single high-speed ^1 line to the computer,

32

4 ■

m '

r ■'■

mk)["

_L

Task 10

Using the completed definitions from Task 9 and the information in the text below, fill in the gaps in this diagram.

Accounts

_I¹

i

2 3 4 5 6 7

''- signals

-- signals

10

Analog transmission

The older telephone systems function on the basis of analog signals representing voice modulation patterns which are represented by variations in wave forms. When using telephone lines for transmitting data by terminal to a computer, the digital signals from the terminal need to be converted to analog signals by an acoustic coupler or modem prior to transmission. A modem is a device which serves a dual purpose because it acts as a MOdulator (digital to analog) and DEModulator (analog to digital), hence the name MODEM. An analog communication system requires a modem at either end of the communication line. When the signals are received by the distant computer, the signals are reconverted to digital form prior to being input for processing.

33

Reading

Task 11 Before 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 10 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.

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I I I

_I

C L

Task 12

Speaking

Work 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.

cc

Local computer

M

M

Remote computer

Student B: Describe diagram 2 to your partner.

M

M

M

M

A C

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AC - Acoustic coupler CC -Clustercontroller M - Modem MP - Multiplexor PC - Personal computer T - Terminal

_c

34

_t

"t

Task 13

Writing

Write a paragraph to show the difference between analog and digital transmission.

_i

Task 14

Word-play Complete the puzzle and find t						he key word 13			in 13 down
1
2
3
4
5
6
7 « 9
10
11						'i
12							\ ■■MM

Across

1 ~^ A combination of electronic devices and conductors that form a conducting

path.(7)

2 i An agreement that covers the procedures used to exchange information

between co-operating computers. (8)

3 j This 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)

5. Single vib ations of electric current. (7)

6 ^A A VDU screen and keyboard used to interact with a computer, usually with no

computing capacity of its own. (8)

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

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

7. A controller controls a number of similar peripheral device such as

terminals and links them to the main computer. (7)

10. This merges information from several channels into one channel. (11)

11. A device that converts the computer's digital bit stream into an analog signal for transmission over a telephone line. (5)

12. A board is a public teleconferencing system that allows users to read and

write messages. (8)

Down

13 The process of sending signals electronically. (12)

35

Language focus C

Word formation: suffixes

We have already seen how prefixes can change the meaning of a word. Let us now consider some suffixes, their usual meanings, and how they change the meanings of English words.

Suffixes

Nouns	Verbs	Adjectives Adverbs
-ance	-ize	-able -ly
-ence	-ate	-ible
-or	-fy	-less
-er	-en	-ic
-ist	-ify	-ical
-ness		-ish
		-ive
	ables and try to make
Exercise 1 Study these t		additional examples. Use your dictionary if
necessary.
1 Noun-forming suffixes:
Suffix	Meaning	Examples
-ance	state	performance
-ence	quality of	independence
r	a person who	programmer, operator
er, -or J	a thing which	compiler, accumulator
-ist, -yst	a person who	analyst, typist
-ian	pertaining to	electrician
-tion, -ation	the act of	compilation
-ness	condition of	readiness
-ion	action/state	conversion
-ing	activity	multiplexing
-ment	state, action	measurement
-ity	state, quality	electricity
-ism	condition/state	magnetism
-dom	domain/condition	freedom
-ship	condition/state	relationship,
		partnership
36

2 Verb-forming suffixes:

Suffix

Meaning

Examples

-ize/-ise -ate

-ify -en

to make

computerize automate, activate, calculate simplify harden, widen

3 Adverb-forming suffix:

Suffix

Meaning

Examples

-ly

in the manner of

electronically, logically, comparably, helpfully

4 Adjective-forming suffixes:

Suffix

Meaning

Examples

-al -ar -ic -ical

-able -ible

-ous

-ful

-less

-ish

-ed -ive

having the quality of

capable of being

Tike, full of

characterized by

without

like

having the quality of

computational, logical

circular

magnetic, automatic

electrical

comparable divisible

dangerous

helpful

careless

yellowish

computed interactive

Exercise 2

1

2

Note: Words ending in -ing are formed from verbs. The -ing form may be used as a noun, part of a noun phrase, or part of a verb.

Examples:

1. Programming is an interesting job. (noun)

2. Programming in C is interesting, (part of noun phrase)

3. He is working as a programmer, (part of verb)

Read the following sentences and circle the suffixes. Underline the stem if it can be used on its own. The first one has been done for you.

A programnxg) designs, writes, and tests programs for perfomxln^ various tasks on acomput@).

A systems analyst studies organizational systems and decides what action needs to be taken to maximize efficiency.

37

3. Laser printers are preferable to other types of printing devices because of their speed and quietness.

4. The microcomputer we have purchased does not have a FORTRAN compiler. It is programmable in BASIC only.

5. We have found that operators who have the freedom to take short breaks during the day greatly improve their performance.

6. The number of shipments will increase over the coming months.

7. We decided to computerize the entire plant to give each division more independence.

8. Spooling is a way of storing data temporarily on disk or tape until it can be processed by another part of the system.

9. Turning your office into a paperless environment may be expensive at the beginning but can produce big savings in the long run.

10 Software developers are producing increasingly sophisticated applications for a growing global market.

Now, for each word that has a suffix, indicate what part of speech the word is (e.g. noun, verb, etc.).

Taski

Programming and language;

Start-up

Can you identify these programming languages?

/* this program finds the minimum of two integers */ #include <stdio.h>