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ФЕДЕРАЛЬНОЕ АГЕНТСТВО ПО ОБРАЗОВАНИЮ
Государственное образовательное учреждение
высшего профессионального образования
САНКТ-ПЕТЕРБУРГСКИЙ ГОСУДАРСТВЕННЫЙ УНИВЕРСИТЕТ
АЭРОКОСМИЧЕСКОГО ПРИБОРОСТРОЕНИЯ
INFORMATION AND INFOSERVICE
Методические указания и учебные задания по развитию навыков
профессионально-ориентированного чтения
АНГЛИЙСКИЙ ЯЗЫК
Санкт-Петербург
2007
Составители: И. В. Вихриева, О. В. Злобина, Д. С. Исаева, М. В. Мальцева
Под редакцией канд. филол. наук доцента Д. С. Исаевой
Рецензент: канд. филол. наук доцент И. И. Громовая
Методические указания содержат материал для обучения различным
видам чтения – ознакомительному, изучающему, поисковому и
просмотровому, и выработки навыков построения монологического
высказывания.
Текстовый материал является аутентичным. Тексты снабжены
заданиями, направленными на усвоение и закрепление полученной
информации, что позволяет овладеть базовыми навыками анализа
информации, и обеспечивает свободную ориентацию в подъязыке
специальности с выходом в профессионально обусловленную
коммуникацию.
Предназначены для студентов 3 курса, обучающихся специальности
«Информационный сервис».
Подготовлены кафедрой иностранных языков и рекомендованы к
изданию редакционно-издательским советом Санкт-Петербургского
государственного университета аэрокосмического приборостроения.
Сдано в набор 00. 07. 07. Подписано к печати 05. 12. 07.
Формат 60×84 1/16. Бумага офсетная. Печать офсетная. Усл. печ. л. 3,3.
Уч.-изд. л. 3,1. Тираж 200 экз. Заказ № 672
Компьютерная верстка Д. С. Исаева, Д. Мельников
Редакционно-издательский центр ГУАП
190000, Санкт-Петербург, Б. Морская ул., 67.
© ГУАП, 2007
UNIT 1
COMMUNICATION
1.1 Communication
Read the text without consulting the dictionary and summarize the
information given in it:
What is communication? The dictionary defines it as “giving or
exchanging information or news by speaking or writing”.
In today’s world, long-distance communication is easy. We can call
people on the telephone, send them telegrams, or write them letters. We
receive news and other information on radio or television every day. Our
modern inventions allow us to communicate with people in every part of
our planet.
In early times, how did people communicate over long distances? How
did they tell other people about a storm that was coming or an enemy who
was planning to attack?
At first, people probably used their feet. When the people of one village
wanted to send a message to someone who was far away, they gave the
news to a runner. This messenger ran to the nearest village and gave the
message to another runner. Then the second runner took it to a third runner,
and so on.
This was a very slow method of communication, and the message
didn’t always reach its destination. The messengers had to run through
forests and fields, cross rivers, and climb mountains. Sometimes they met
wild animals and never arrived at the next village. And the messages
frequently became mixed up, because each person who relayed1 the
information changed it a little.
People used other methods of communication, too. Cyrus the Great2,
who founded the Persian Empire, built a series of towers. A man with a
very strong voice stood on each tower. When the king wanted to send a
message, he gave it to the man on the first tower, who shouted it to the man
on the second tower, and relayed it to the man on the third tower. These
messengers usually used megaphones, which made their voices louder.
The use of fire and smoke was another primitive way of
communication. This method wasn’t very efficient on rainy days or at
night, and little wind could mix up the message very badly.
A few old methods of communication are still in use today. One of
these methods is the use of drums. When the drummer hits the drum, it
3
makes a noise that sounds a little like human speech. Drumbeats travel
quickly, but they can travel only a little way.
In 1790, a man in France invented the semaphore, which was a tall
pole3 with “arms” at the top. Ropes4 moved the arms up and down to form
letters of the alphabet. Semaphore operators were able to relay messages
very quickly. A kind of semaphore is still in use on the railroads.
Efficient long-distance communication had to wait for the discovery of
electricity. Scientists were carrying on experiments with electricity during
the whole 18th century. Finally in the 19th century people saw the first really
practical application of electricity in the field of communications. In 1844
Samuel F. B. Morse constructed the first electric telegraph. Within a few
years telegraph systems worked in many countries of the world.
About thirty years after Morse established his first telegraph system
Alexander Graham Bell sent the human voice over long distances by means
of electricity. His invention was the telephone.
Scientists and inventors of many countries continued to experiment
with communication devices and they produced many inventions. After the
telegraph and the telephone came the wireless telegraph and the radio and
television. An example of the level which communication reached then was
the earth satellites. As these satellites move in their orbits hundreds of
miles above the surface of the earth, they collect important information
about the earth and its atmosphere and send back to earth this information
by means of electrical signals.
Now quick communication over long distances is becoming more
important than ever. The most recent development is the Internet, a global
computer network that embraces millions of users all over the world.
Notes: 1отправлять, пересылать, посылать (сообщение, информацию);
2
Кир Великий; 3столб, шест; 4канат, веревка, трос
1. 2 TELEPHONE
1.2 (1) Telephone
Read and translate the text:
The telephone or phone is a telecommunications device which is used
to transmit and receive sound (most commonly voice and speech) across
4
distance. Most telephones operate through transmission of electric signals
over a complex telephone network which allows almost any phone user to
communicate with almost any other.
An elementary telephone system consists of two elements: for each
subscriber1, the system must contain the equipment necessary to convert
sound to electrical signals and back. This equipment is called the
"telephone" and allows users to speak and hear each other. Most telephones
are in two parts: The handset is a handle containing the transmitter and
receiver. The base contains a dial to initiate a call and a bell or other
signalling device to notify the user of a telephone call from another user.
Some telephones have more or fewer parts, and some don't have this kind
of integrated handset².
The system must connect the two or more telephones together.
Historically, and still usually, this is by means of twisted pair wire3, and
usually via the worldwide telephone network4. Sometimes it is by radio, as
in a cellular, satellite or radiotelephone or sometimes by voice over Internet
protocol 5, which uses a broadband internet connection.
The very early history of the telephone is a confusing morass6 of claim
and counterclaim, which was not clarified by the huge mass of lawsuits
which hoped to resolve the patent claims of individuals. The Bell and
Edison patents however were forensically victorious and commercially
decisive.
Notes: 1каждый подписчик; 2сложная телефонная трубка; 3пара
скрученного провода; 4всемирная телефонная сеть; 5протокол сети
Интернет; 6беспорядочная, запутанная трясина
Questions and tasks to the text:
1)
2)
3)
4)
5)
What is telephone?
How do most telephones operate?
Illustrate an elementary telephone system.
State that most telephones are in two parts.
Give some examples you know of connecting system. Can you
think of cases where it has occurred?
6) Why is the very early history of the telephone considered to be a
confusing morass of claims and counterclaims?
5
1.2 (2) Signalling
Read and translate the text:
Signalling began in an appropriately primitive manner1. The user
alerted the other end, or the exchange operator, by whistling into the
transmitter. Exchange operation soon resulted in2 telephones being
equipped with a bell, first operated over a second wire and later with the
same wire using a condenser.
Rural3 and other telephones that were not on a common battery
exchange had a “magneto” or hand cranked generator to produce a high
voltage alternating signal to ring the bells of other telephones on the line
and to alert the operator.
In the 1890s a new smaller style of telephone was introduced, packaged
in three parts. The transmitter stood on a stand, known as a “candlestick”4
for its shape. When not in use, the receiver hung on a hook with a switch in
it, known as a “switchhook”5. Previous telephones had required operating a
separate switch to connect either the voice parts of the telephone or the bell.
With the new kind, they less often forgot and left the phone “off the hook”.
The bell, induction coil, battery and magneto were in a separate “bell box”
if it was a magneto exchange.
Disadvantages of single wire operation such as crosstalk and hum from
nearby AC6 power wires had already led to the use of twisted pairs and, for
long distance telephones, four-wire circuits. Users at the beginning of the
20th century did not place long distance calls from their own telephones but
made an appointment to use a special sound proofed long distance
telephone booth7 furnished with the latest high technology equipment
where, for a workingman's week's pay, they could sit comfortably for three
minutes and shout across hundreds of miles without waking the neighbors.
What turned out to be the most popular and long lasting physical style
of telephone was introduced in the early 20th century. Transmitter and
receiver were united in a single molded plastic handle, which when not in
use sat in a cradle in the base unit. After the 1930s the base also enclosed
the bell and induction coil, obviating the old separate bell box. For the next
half century, the network behind the telephone became progressively
larger8 and much more efficient, but after the dial was added the instrument
itself changed little.
6
Notes:1примитивным образом; 2привело к; 3сельский, деревенский;
4
подсвечник; 5телефонный рычажок; 6(alternating current ) переменный
ток; 7телефонная будка; 8значительно шире
Questions аnd tasks to the text:
1) How did signaling begin?
2) What soon resulted in telephones being equipped with the bell?
Why?
3) Why did rural telephones have cranked generator?
4) Illustrate the introduction of a new smaller style of telephone.
5) Trace through disadvantages of single wire operation.
6) Did telephone users at the beginning of the 20 the century feel
comfortable while talking on phone. Why?
For Your Information
Read texts 1.2 (3), 1.2 (4), and 1.2 (5) without consulting the dictionary and
comment on main ideas.
1.2 (3) Instant Messaging
Instant messaging or IM is a form of real-time communication
between two or more people based on typed text. The text is conveyed via
computers connected over a network.
Instant messaging requires the use of a client program that hooks up
an instant messaging service and differs from e-mail in that conversations
are then able to happen in real time. Most services offer a presence
information feature, indicating whether people on one's list of contacts are
currently online and available to chat. This may be called a contact list.
In early instant messaging programs, each letter appeared as it was
typed, and when letters were deleted to correct typos this was also seen in
real time. This made it more like a telephone conversation than exchanging
letters. In modern instant messaging programs, the other party in the
conversation generally only sees each line of text right after a new line is
started. Most instant messaging applications also include the ability to set a
status message, roughly analogous to the message on a telephone
answering machine.
7
1.2 (4) IM Benefits
Instant messaging typically boosts communication and allows easy
collaboration. In contrast to e-mails, the parties know whether the peer is
available. Most systems allow the user to set an online status or away
message so peers get notified whenever the user is available, busy, or away
from the computer.
On the other hand, people are not forced to reply immediately to
incoming messages. This way, communication via instant messaging can
be less intrusive than communication via phone, which is partly a reason
why instant messaging is becoming more and more important in corporate
environments. However, not all popular systems allow the sending of
messages to people not currently logged on (offline messages), a vital
feature when to be used as a less formal e-mail replacement.
It is possible to save a conversation, so as to refer to it later, which is
not possible by telephone. Also, the fact that instant messages typically get
logged in a local message history closes the gap to the persistent nature of
e-mails, facilitating quick, safe, and persistent exchange of information.
Instant messaging has been known to greatly improve (mostly) children's
typing ability, a skill that is becoming increasingly important for the benefit
of today's youth.
1.2 (5) Mobile Instant Messaging
Mobile Instant Messaging is a presence enabled messaging service that
aims to transpose the desktop messaging experience to the usage scenario
of being on the move. While several of the core ideas of the desktop
experience aim to apply to a connected mobile device, others do not: Users
usually only look at their phone's screen - presence status changes might
occur under different circumstances as happens at the desktop, and several
functional limits exist based on the fact that the vast majority of mobile
communication devices are chosen by their users to fit into the palm of
their hand.
Some of the form factor and mobility related differences need to be
taken into account in order to create a really adequate, powerful and yet
convenient mobile experience: radio bandwidth, memory size, availability
of media formats, keypad based input, screen output, CPU performance and
battery power are core issues that desktop device users and even nomadic
users with connected notebooks are usually not exposed to.
8
Several large scale mobile telephone industry companies are planning
to jointly deliver a ubiquitous, interoperable presence enabled messaging
service, built according to interoperability recommendations developed in
the GSM Association.
Tasks on the section:
1) On the basis of the texts in this section make a report on instant
messaging. Mention the idea of early instant messaging programs.
2) Describe benefits of instant messaging.
3) Indicate the general approach of mobile instant messaging.
4) Why do some large mobile telephone industry companies plan to
deliver presence enabled messaging service?
1.3 RADIO
1.3 (1) Radio Network
Read and translate the text:
A radio network is a network system which distributes programming to
multiple stations1 simultaneously, or slightly delayed2 for the purpose of
extending total coverage beyond the limits of a single broadcast signal. The
resulting expanded audience for programming essentially applies the
benefits of mass-production to the broadcasting enterprise3.
Most radio networks also produce much of their programming.
Originally, radio networks owned some or all of the radio stations that
broadcast the network's programming. Presently however, there are many
networks that do not own any stations and only produce and/or distribute
programming. Similarly station ownership does not always indicate
network affiliation4. A company might own stations in several different
markets and purchase programming from a variety of networks.
Radio networks rose rapidly with the growth of regular broadcasting of
radio to home listeners in the 1920s. This growth took various paths in
different places. In Britain the BBC was developed with public funding, in
the form of a broadcast receiving license, and a broadcasting monopoly in
its early decades. In contrast, in the United States of America various
competing commercial networks arose funded by advertising revenue5. In
9
that instance, the same corporation that owned or operated the network
often manufactured and marketed the listener’s radio.
Major technical challenges to be overcome when distributing programs
over long distances are maintaining signal quality and managing the
number of switching/relay points6 in the signal chain. Early on, programs
were sent to remote stations7 (either owned or affiliated) by various
methods, including leased telephone lines, on pre-recorded gramophone
records or audio tape, and somewhat later via microwave relay stations.
Later on coaxial cable linking stations became the norm, as it provided the
best cost-benefit ratio.
Notes: 1многочисленные станции; 2слегка приостановленный;
3
транслирующее предприятие; 4присоединение сети; 5доход,
полученный с рекламы; 6реле; 7небольшие, отдаленные станции
Questions and tasks to the text:
1) Define carefully what is meant by a radio network.
2) Prove that radio networks rose rapidly with the growth of regular
broadcasting of radio.
3) Illustrate how the company might own stations in different markets.
4) Spell out the arguments to show that many networks do not own any
stations but only produce and distribute programming.
5) What factors might increase radio networks?
6) Trace through what happens if major technical challenges are overcome.
1.3 (2) Scientific Theory and Verification
Read and translate the text:
The arguments concerning the transmission of information have been
and are driven by perceived profit1 or national pride, and sometimes tends
to consider such issues as “the first practical...”, or whether the
development of radio took place in the inventor's country of birth or not.
James Clerk Maxwell performed the theoretical physical research
that correctly predicted the existence of radio (and all other
electromagnetic) waves.
10
Heinrich Rudolf Hertz was the experimental physicist who created
radio waves in a controlled laboratory manner. Both Maxwell and Hertz,
however, never devised systems for actual general use nor described the
application of the technology.
Developments, parallel to these individuals and after, are engineering
investigations2 that lead to the “invention of radio”: the objects, processes,
or techniques of information transception.
Many individuals contributed to the art of wireless, in the air, earth,
and water; this includes the precursory work3 in wireless telephony and
wireless telegraphy.
David E. Hughes, eight years before Hertz's experiments and nearly
two decades before Marconi's demonstrations, induced electromagnetic
waves in a signalling system. Hughes transmitted Morse code by an
induction apparatus4. In 1878, Hughes's induction transmission method
utilized a “clockwork transmitter"5 to transmit signals.
In 1885, T.A. Edison used a vibrator magnet for induction
transmission. In 1888, Edison deployed a system of signalling. In 1891,
Edison attained the wireless patent for this method using inductance.
From 1886 to 1888 inclusive Heinrich Hertz had proved that the
properties of radio waves were consistent with Maxwell’s electromagnetic
theory6. He demonstrated that radio radiation had all the properties of
waves (now called Hertzian waves), and discovered that the
electromagnetic equations could be reformulated into a partial differential
equation called the wave equation.
1
2
Notes:
осознанная
выгода;
технические
исследования;
3
предварительная работа; 4индукционная катушка; 5радиопередатчик с
точностью часового механизма; 6Электромагнитная теория Максвелла.
Questions and tasks to the text:
1)
2)
3)
4)
5)
6)
Who performed the theoretical physical research?
What did this research predict?
Who created waves in a controlled laboratory manner and why?
Spell out arguments to show the invention of radio.
Illustrate that many individuals contributed to the art of wireless.
Trace through what had happened eight years before Hertz’s
experiments.
11
7) Illustrate that Hertz had proved that properties of radio waves were
consistent with Maxwell’s Electromagnetic Theory.
For your information
Read texts 1.3 (3), 1.3 (4) and 1.3 (5) without consulting the dictionary and
give a short (3-5 sentences), either written or oral, summary of each.
1.3 (3) The Hertz Antenna
Of the three basic forms of wireless aerial launching structures, the
Hertz antenna was a center-fed half-wavelength dipole. Hertz’s setup for a
source and detector of radio waves (archaically called Hertz waves in his
honor) comprised a primitive radio system capable of transmitting and
receiving space waves through free space.
His transmitter was not at all efficient and was severely limited in
power output. Its dipole antenna differed from the vertical quarterwavelength antenna that was subsequently adopted by Marconi and others
in that it was not grounded.
Hertz used the damped oscillating currents in a dipole antenna,
triggered by a high-voltage electrical capacitive spark discharge, as his
source of radio waves. His detector in some experiments was another
dipole antenna connected to a narrow spark gap. A small spark in this gap
signified detection of the radio wave. When he added cylindrical reflectors
behind his dipole antennas, Hertz could detect radio waves about 20 meters
from the transmitter in his laboratory. He did not try to transmit further
because he wanted to prove the electromagnetic theory, not to develop
wireless communications.
Hertz was uninterested in practical importance of his experiments.
The art of radio was left to others to implement into a practical useful form.
His discoveries would later be taken up by entrepreneurs looking to make
their fortunes. Marconi's 1895 experiments followed Hertz's work (among
others) by using a spark source in what became known as a spark-gap
transmitter.
1.3 (4) Tesla's Work
Nikola Tesla was Serbian/Croatian/Austro-Hungarian/American
inventor, physicist, mechanical engineer and electrical engineer who some
Americans regard as one of the most important inventors in history.
12
Nikola Tesla was one of the first to patent a means to reliably produce
radio frequency currents. Tesla’s “Method of Operating Arc-Lamps”
(March 10, 1891), describes an alternator that produced high-frequency
current (for that time period), around 10,000 cycles per second. (The term
cycles-per-second was later modified to “Hertz”.) His patentable innovation
was suppression of the sound produced by arc lamps that operated on
alternating or pulsating current by using frequencies beyond the range of
human hearing. The alternator produced frequencies in the Very Low
Frequency (VLF) band.
Around July 1891, he established his New York laboratory and
constructed various apparatuses that produced between 15,000 to 18,000
cycles per second. At this location, he also lit vacuum tubes wirelessly
(thus providing hard evidence for the potential of wireless transmissions).
Transmission and radiation of radio frequency energy was a feature
exhibited in the experiments by Tesla and was noted early on to be used for
the telecommunication of information.
In 1892, Tesla delivered a widely reported presentation before the
Institution of Electrical Engineers of London in which he noted, among
other things, that intelligence would be transmitted without wires. Later, a
variety of Tesla's radio frequency systems were demonstrated during
another widely known lecture, presented to meetings of the National
Electric Light Association in St. Louis, Missouri and the Franklin Institute
in Philadelphia.
1.3(5) Tesla Transmitters
An early Tesla tramsmitter consisted of a flat-spiral quarterwave
resonator and an elevated terminal.
Early on in his research Tesla used his high voltage resonance
transformer - the Tesla coil - in radio-wave propagation experiments. The
aerial consisted of a top-loaded electrical conductor that was connected to a
high-voltage terminal of the transformer. The opposing high-voltage
terminal was grounded. The secondary winding was driven by a primary
circuit consisting of a few turns of heavy wire, a capacitor bank, a circuit
controller, and a power supply transformer. The launching structure
radiated as a common “Hertz wave” antenna.
After a while he began to favour another technique that he called the
“disturbed charge of ground and air method.” Tesla's wireless system used
the same basic apparatus, however instead of using electromagnetic space
13
waves the energy is carried by the conduction of electrical currents through
the earth and along with accompanying surface waves. In one form of the
system the “return” path closing the circuit is an electrical current flow
established between two elevated terminals, one belonging to the
transmitter and the other to the receiver. These consist of conduction
currents flowing through plasma and also electrostatic induction.
In other words, Tesla’s structure injected a large alternating current into
the earth via the ground terminal. Tesla's discovery of importance was the
“Surface wave” method.
Tasks on the section:
1) On the basis of the texts in this section make a report on properties
of radio waves. Mention the idea of radio network development.
2) Describe Hertz waves of wireless communication.
3) Indicate the general approach of the American inventor and
engineer Nikola Tesla.
1.4 TELEVISION
1.4 (1) Television Network
Read and translate the text:
A television network is a distribution network1 for television content
whereby a central operation provides programming for many television
stations. Until the mid 1980s, television programming in most countries of
the world was dominated by a small number of broadcast networks. Many
early television networks (e.g. the BBC2, NBC3 or CBS4) evolved from
earlier radio networks. It may be confused with a television channel.
Within the industry, a tiering 5 is sometimes created among groups of
networks based on whether their programming is simultaneously originated
from a central point, and whether the network master control has the
technical and administrative capability6 to take over the programming of
their affiliates in real time when it deems this necessary - the most common
example being breaking national news events.
In countries where most networks broadcast identical, centrally
originated content from all their stations and where most individual stations
14
are therefore nothing more than large “repeater stations”7 the terms
television network, television channel and television station have become
interchangeable in everyday language, with only professionals in TVrelated occupations continuing to make a difference between them, if one
was ever made. This applies to most countries outside Northern America,
the United Kingdom, Australia and Japan.
However, in North America in particular, many television channels
available via cable and satellite television8 are branded as “networks” but
are not truly networks in the sense defined above, as they are singular
operations – they have no affiliates9 or component stations. Such channels
are more precisely referred to as “specialty channels” (Canada) or “cable
networks” (U.S.), although the latter term is somewhat incorrect.
In the U.S., television networks are simply identified as “networks”
(such as ABC10, CBS or NBC), while the local stations are identified by the
station call sign and city of license. In Europe and much of Asia, Africa and
South America, television networks are often more or less numbered, for
example Britain's BBC One, BBC Two, ITV, Channel Four and Five etc, or
the Netherlands' Nederland 1, Nederland 2, Nederland 3. In Australia,
television networks are identified by the channel number in the capital
cities (such as Seven, Nine or Ten).
Notes:1распределительная сеть; 2Британская вещательная корпорация,
3
радио
и
телевещание
компании
Эн-Би-Си;
Би-Би-Си;
4
радиовещательная
и
телевизионная
компания
«Коламбия
бродкастинг систем» - Cи-Би-Эс; 5распределение по рядам;
6
административная способность; 7«повторяющиеся станции»; 8каналы,
транслирующие передачи посредством кабельного и спутникового
телевидения; 9филиал; 10американская радиовещательная компания,
Эй-Би-Си
Questions and tasks to the text:
1)
2)
3)
4)
What is a television network and what does it provide?
How did many early television networks evolve?
Show that most networks broadcast identically.
Spell out arguments to show that most TV networks are nothing but
large “repeater stations”.
15
5) Why many TV channels are available via cable and satellite TV
branded as “networks” in North America?
6) How are television networks and local stations identified?
1.4 (2) The History of Television Network
Read and translate the text:
NBC1 set up the first permanent coast-to-coast radio network in the
United States by 1928, using dedicated telephone line technology. But the
signal from an electronic television system, containing much more
information than a radio signal, required a broadband transmission
medium. Transmission by a nationwide series of microwave relay towers2
would be possible but extremely expensive.
Researchers at the AT&T (American Telephone and Telegraph
Company) subsidiary Bell Telephone Laboratories patented coaxial cable
in 1929, primarily as a telephone improvement device. But its high
capacity3 (transmitting 240 telephone calls simultaneously) also made it
ideal for long-distance television transmission, where it could handle a
frequency band of 1 megahertz. German television first demonstrated such
an application4 in 1936 by relaying televised telephone calls from Berlin to
Leipzig, 180 km (112 miles) away, by cable. The network was later
extended to television viewing offices in Nurenberg and Munich.
NBC had earlier demonstrated an inter-city television broadcast5 on
February 1, 1940, from its station in New York City to another in
Schenectady, New York, by General Electric relay antennas, and began
transmitting some programs on an irregular basis to Philadelphia and
Schenectady in 1941. Wartime priorities6 suspended the manufacture of
television and radio equipment for civilian use from April 1, 1942 to
October 1, 1945, temporarily shutting down7 expansion of television
networking.
AT&T made its first postwar addition in February 1946, with the
completion of a 225-mile (362 km) cable between New York City and
Washington, D.C., although a blurry8 demonstration broadcast showed that
it would not be in regular use for several months. NBC launched what it
called “the world's first regularly operating television network” on June 27,
1947, serving New York, Philadelphia, Schenectady and Washington.
Baltimore and Boston were added to the NBC television network in late
1947.
16
Notes: 1радио и телевещание компании Эн-Би-Си (National
Broadcasting Company); 2башня, вышка; 3высокая пропускная
4
5
способность;
применение;
телевещание
между
городами;
6
7
приоритеты военного времени; закрыть; 8нечеткий, неясный
Questions and tasks to the text:
1) When did NBC set up the first permanent coast-to-coast radio
network in the US? Why was it important?
2) When did researchers at AT&T patent coaxial cable?
3) Comment on arguments to show that primarily it was a telephone
improvement device. Who first demonstrated it?
4) Spell out arguments to demonstrate transmitting some programmes
on an irregular basis.
5) What was its first postwar addition that AT&T made? Was it in
regular use?
For Your Information
Read text 1.4 (3) without consulting the dictionary and give a short (3-5
sentences), either written or oral, summary of it.
1.4 (3) Let’s Put the Vision in Television!
Television has a vital role to play in helping us move towards a more
humane and sustainable planet.
Sooner or later, any meaningful process of renewal has to involve large
numbers of people, and that will undoubtedly require making use of the
best communications tools available. Two years ago, after completing the
book Voluntary Simplicity, Duane Elgin began working to build the
foundation for a national media reform. With Ann Niehaus, he co-founded
“Choosing Our Future”, a non-profit organization not supporting any
political party whose goal was to promote a more active democratic and
communicating society.
Their specific objective has been a new generation of public affairs
programming on TV that would explore, with depth and diversity, the
major challenges facing the United States. In the past two years, they have
done extensive research on changes in public attitudes towards television
and on its role in our democracy; held meetings with groups of citizens in
17
various parts of the country to discuss people's programming needs;
conducted a pilot petition campaign that called upon the television industry
to devote one-third of prime-time hours to “reality-based” or “socially
relevant” programming; and established a network of contacts with media
professionals around the country.
Tasks on the section:
On the basis of the text in this section make a report on the role TV
networks can play in our life. Mention the idea of public affairs
programming on TV.
UNIT 2
INFORMATION
2.1 Information as a Powerful Resource
Read the text without consulting the dictionary and summarize the
information given in it:
Information is a powerful resource, which helps not only in being
aware of everything that is around us and arouses our interest, but also it
enables us to communicate with each other more efficiently, to exchange
our thoughts in a higher level, to use modern information technologies for
our everyday life. How to make a real use of information?
Information is everything around us, but we should keep in mind the
fact, that it’s also an unlimited resource. So we must know how to omit the
unnecessary information and find the ways to concentrate only on needed
information that would help us to reach any kind of goal.
Nowadays, to get the necessary information you don’t have to spare
much time. The most productive way of receiving useful data is Internet
and other information technologies. In Internet, for instance, you can find
information about any company, buy or sell any good or service, find out
about modern tendencies in fashion, design, you even can read the freshest
news or communicate with your friend from another country without
leaving your house. Information technologies help to economize our time
and efforts while searching any facts.
18
What role does information play in business environment? Information
helps every business to innovate and to broad its opportunities. With the
help of information technologies a company can make close contacts with
customers, expand the range of services, and make easier for people a
process of buying its goods.
As we see, information has become our major commodity, our helper
and advisor, which covers more and more useful facts before us.
2.2 Information Technology
Read and translate the text:
Information technology (IT), as defined by the Information Technology
Association of America (ITAA1) is: “the study, design, development,
implementation, support or management of computer-based information
systems, particularly software applications and computer hardware”. In
short, IT deals with the use of electronic computers and computer software
to convert, store, protect, process, transmit and retrieve2 information. In this
definition, the term “information” can usually be replaced by “data”
without loss of meaning. Recently it has become popular to broaden the
term to include the field of electronic communication so that people tend to
use the abbreviation ICT (Information and Communication Technology).
IT professionals perform a variety of duties that range from installing
applications to designing complex computer networks and information
databases. A few of the duties of IT professionals may include:
▪
Data Management
Data management comprises all the disciplines related to managing data
as a valuable resource. It is the development and execution of architectures,
policies, practices and procedures that properly manage the full data
lifecycle.
▪
Computer Networking
Computer networking is communication between computer systems.
Such communicating computer systems constitute a computer network and
these networks generally involve at least two devices. The devices can be
separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances
(e.g. via the Internet). Examples of networks are a small home local area
19
network (LAN3) with two computers connected by standard networking
cables to a network interface card4 in each computer, or the Internet, a wide
area network5 that is the largest to ever exist.
▪
Software design
Software design is a process of problem-solving and planning for a
software solution. After the purpose and specifications of software are
determined, software developers will design or employ designers to
develop a plan for a solution.
If the software is user centered, software design may involve user
experience to help determine those specifications. If the software is
completely automated (meaning no user or user interface), a software
design may be as simple as a flow chart6 or text describing a planned
sequence of events. In either case some documentation of the plan is
usually the product of the design.
▪
Management Information Systems (MIS)
Management Information Systems is the application of people,
technologies, and procedures - collectively, the information system - to
business problems. It can also help in gathering and processing specific
information for decision making.
Notes:1Американская ассоциация по информационным технологиям;
искать, находить; 3локальная вычислительная сеть; 4сетевая
интерфейсная плата, сетевой адаптер (контроллер); 5глобальная
вычислительная сеть; 6блок-схема
2
Questions and tasks to the text:
1) Define the notion IT in short.
2) Do you agree that the term “information” can be replaced by
“data”? Why and why not?
3) Does the field of IT include electronic communication?
4) Name some duties of IT professionals. Which duty, in your
opinion, is the most popular nowadays?
5) Summarize what is said about: data management, computer
networking, software design, and management information
systems.
20
Summarize the information of the text and comment on the area of IT
application.
2.3 Information Theory
Read and translate the text:
Information theory is a discipline in applied mathematics1 involving the
quantification2 of data with the goal of enabling as much data as possible to
be reliably stored on a medium or communicated over a channel. The
measure of information, known as information entropy3, is usually
expressed by the average number of bits needed for storage or
communication.
Information theory is generally considered to have been founded in
1948 by Claude Shannon in his work A Mathematical Theory of
Communication. The central framework of classic information theory is the
engineering problem of the transmission of information over a noisy
channel.
Applications of fundamental topics of information theory include
lossless data compression4 (e.g. ZIP files5), lossy data compression6 (e.g.
MP3s), and channel coding (e.g. for DSL lines7). The field is at the
crossroads of mathematics, statistics, computer science, physics,
neurobiology8, and electrical engineering. Its impact has been crucial to
success of the Voyager missions to deep space, the invention of the CD, the
feasibility of mobile phones, the development of the Internet, the study of
linguistics and of human perception, the understanding of black holes, and
numerous other fields. Information theory is also used in information
retrieval, intelligence gathering9, gambling, statistics, and even in musical
composition.
The main concepts of information theory can be grasped by considering
the most widespread means of human communication: language. Two
important aspects of a good language are as follows. First, the most
common words (e.g., “a”, “the”, “I”) should be shorter than less common
words (e.g., “benefit”, “generation”, “mediocre”), so that sentences will not
be too long. Such a tradeoff10 in word length is analogous to data
compression and is the essential aspect of source coding. Second, if a part
of a sentence is unheard or misheard due to noise - e.g., a passing car - the
21
listener should still be able to understand the meaning of the underlying
message. Such robustness11 is as essential for an electronic communication
system as it is for a language; proper building such robustness into
communications is done by channel coding. Source coding and channel
coding are the fundamental concerns of information theory.
Note that these concerns have nothing to do with the importance of
messages. For example, a phrase such as “Thank you; come again” takes
about as long to say or write as urgent, “Call an ambulance!” while clearly
the latter is more important and more meaningful. Information theory,
however, does not involve message importance or meaning, as these are
matters of the quality of data rather than the quantity of data, the latter of
which is determined solely by probabilities.
Notes: 1прикладная математика; 2определение количества; 3энтропия
(греч. поворот, превращение) здесь: информационная энтропия - мера
хаотичности информации, связанная с вероятностью появления тех
или иных символов при передаче сообщений; 4сжатие информации без
потерь; 5самый распространенный стандарт сжатия файлов и формат
архивов на FTP-серверах; 6сжатие информации с потерями; 7сокр. от
digital subscriber line - цифровая абонентская линия; 8нейробиология;
9
сбор информации (сведений); 10выбор оптимального соотношения;
компромиссное решение; 11устойчивость (мат.)
Questions and tasks to the text:
1) Define the notions: information theory, information entropy, source
coding, and channel coding.
2) Name the fields where information theory is used.
3) What did the development of information theory result in?
4) Indicate the main concepts of information theory.
5) What is the essential aspect of source coding?
6) What is more important in information theory: the quality of data
or the quantity of data?
Sum up what you have learned about information theory.
22
2.4 Coding Theory
Read and translate the text:
Coding theory is the most important and direct application of
information theory. It can be subdivided into source coding theory and
channel coding theory. Using a statistical description for data, information
theory quantifies the number of bits needed to describe the data, which is
the information entropy of the source.
▪
Data Compression (Source Coding)
There are two formulations for the compression problem:
- lossless data compression with which the data must be reconstructed
exactly;
- lossy data compression allocates bits needed to reconstruct the data.
▪
Error Correcting Code (Channel coding)
While data compression removes as much redundancy1 as possible, an
error correcting code adds just the right kind of redundancy (i.e. error
correction) needed to transmit the data efficiently and faithfully across a
noisy channel.
This division of coding theory into compression and transmission is
justified2 by the information transmission theorems, or source-channel
separation theorems that justify the use of bits as the universal currency for
information in many contexts. However, these theorems only hold in the
situation where one transmitting user wishes to communicate to one
receiving user. In scenarios with more than one transmitter (the multipleaccess channel), more than one receiver (the broadcast channel) or
intermediary “helpers” (the relay channel), or more general networks,
compression followed by transmission may no longer be optimal. Network
information theory refers to these multi-agent communication models.
Coding theory is concerned with finding explicit methods3, called codes,
of increasing the efficiency and reducing the net error rate of data
communication over a noisy channel to near the limit that Shannon proved
is the maximum possible for that channel. These codes can be roughly
subdivided into data compression (source coding) and error correction
(channel coding) techniques. In the latter case, it took many years to find
the methods Shannon's work proved they were possible. A third class of
23
information theory codes are cryptographic algorithms (both codes and
ciphers). Concepts, methods and results from coding theory and
information theory are widely used in cryptography and crypto analysis.
Notes: 1избыточность; 2объяснять, подтверждать, доказывать; 3точный,
подробно разработанный
Questions and tasks to the text:
1) What applications of information theory exist (except coding
theory)?
2) What is information entropy?
3) Explain the notions: source coding theory, channel coding theory,
lossless data compression, and lossy data compression.
4) In what cases might compression followed by transmission be
optimal?
5) What is coding theory concerned with?
Sum up what you have learned about coding theory.
2.5 MP3
Read the text without consulting the dictionary and give a short (6-8
sentences), either written or oral, summary of it:
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a
popular audio encoding format. It uses a lossy compression algorithm that
is designed to greatly reduce the amount of data required to represent the
audio recording, yet still sound like a faithful reproduction of the original
uncompressed audio to most listeners. It was invented by a team of
European engineers at the end of the 1980s.
When creating an MP3 file, there is a trade-off between the amount of
space used and the sound quality of the result. Typically, the user is
allowed to set a bit rate, which specifies how many kilobits the file may use
per second of audio. The lower the bit rate used, the lower will be the audio
quality. Likewise, the higher the bit rate used the higher quality the
resulting MP3 will be.
24
MP3 files encoded with a lower bit rate will generally play back at a
lower quality. As well as the bit rate of the encoded file, the quality of MP3
files depends on the quality of the encoder and the difficulty of the signal
being encoded. As the MP3 standard allows quite a bit of freedom with
encoding algorithms, different encoders may feature quite different quality,
even when targeting similar bit rates.
In the first half of 1995 through the late 1990s, MP3 files began to
spread on the Internet. MP3's popularity began to rise rapidly with the
advent1 of Nullsoft's audio player Winamp (released in 1997), the UNIX
audio player mpg123 and the peer-to-peer file sharing network2 Napster
(released in 1999). These programs made it simple for average users to play
back, create, share and collect MP3s.
The small size of MP3 files has enabled widespread peer-to-peer file
sharing of music, which would previously have been impossible. The major
record companies, who argue that such free sharing of music reduces sales,
reacted to this by pursuing law-suits3 against Napster, which was eventually
closed down, and eventually against individual users who engaged in file
sharing.
Despite the popularity of MP3, online music retailers often use other
proprietary4 formats that are encrypted (known as Digital Rights
Management) to prevent users from using purchased music in ways not
specifically authorised by the record companies. The record companies
argue that this is necessary to prevent the files from being made available
on peer-to-peer file sharing networks. However, this has other side effects
such as preventing users from playing back their purchased music on
different types of devices. Some services, such as eMusic, continue to offer
the MP3 format, which allows users to playback their music on virtually
any device.
Notes: 1наступление, приход; 2(peer-to-peer сокр. P2P) совместное
использование файлов в децентрализованной, пиринговой сети;
3
предъявлять иск, вести судебное дело; 4патентованный, собственный
For Your Information
Read texts 2.6 and 2.7 without consulting the dictionary and comment on
their main ideas.
25
2.6 Summing up the 20th Century
Technology made modern society possible. It added to leisure time and
reduced the long hours of work. Technology can allow the world to feed
itself. It reduced the effects of natural catastrophes. The world is now a
smaller place where people can communicate with each other and travel
rapidly everywhere.
The establishment of the moving assembly line by Henry Ford in 1913
made automobiles inexpensive enough and allowed to produce cars at a
record-breaking rate. Technology raised the standard of living. The 20th
century has become the century of many inventions. New materials
(synthetic rubber, artificial fabrics and plastics) affected the ways of life
and fashion.
Electronics was ushered in1 when Marconi sent the first Transatlantic
radio message in 1901. Radio and television changed communication and
entertainment habits. In 1948 the transistor was invented, and the era of
modern computers was started.
In 1957 the Space Age began, when the first Earth-orbiting satellite –
Sputnik – was launched by the Soviet Union.
Medical technology was expanded by the use of new medicines and
new equipment. New technologies in biology led to genetic engineering, in
which living cells can be altered. In 1996 a lamb called Dolly became the
first large animal, which was cloned from the genetic material extracted
from the adult cell.
Technology keeps advancing at a rapid rate. It can only be guessed
what the “information revolution” of the late 20th century will bring about.
What will the next century be? Let’s take that risk and peer into the
future. In the digital realm, the next big advance will be voice recognition.
In a decade or so we’ll be able to chat not only with our computers but
automobile navigation systems, thermostats, microwaves and any other
device we want to boss2 around. That will open the way to the next phase
of the digital age: artificial intelligence. By our providing so many thoughts
to our machines each day, they’ll accumulate enough information about
how we think so that they’ll be able to mimic3 our minds. Scary4? But
potentially quite useful. At least until they decide they don’t need us any
more and start building even smarter machines they can boss around. The
digital revolution is likely to pale in comparison to the revolution in
biotechnology that is just beginning.
26
Among the few things certain about the coming century is that it will
be wired, networked and global. Because national borders will be unable to
block the flow of information and innovation.
Notes: 1вводить, возвещать приход чего-л.; 2управлять, распоряжаться;
подражать, имитировать; 4жутко.
3
2.7 To Depend on Computers – Is it Bad or Not?
Computers are a relatively new invention. The first computers were
built some fifty years ago and it is only in the last 30 or so years, that their
influence has affected our everyday life. Personal computers were
introduced as recently as the early 1980s. In this short time they made a
tremendous impact on our lives. We are now so dependent on computers
that it is hard to go into a bank, when their main computer is broken. Just
try to appreciate the chaos that would occur if computers were suddenly
removed worldwide.
In the future computers will be used to create bigger and even more
sophisticated1 computers. The prospects for this are quite alarming. They
will be so complex; that no individual could hope to understand how they
work. They will bring a lot of benefits2, but they will also increase the
potential for imaginable chaos. They will, for example, be able to fly planes
and they will be able to coordinate the movements of several planes in the
vicinity3 of an airport. Providing4 all the computers are working correctly,
nothing can go wrong. If one small program fails – disaster5.
There is a certain inevitability6 that technology will progress and
become increasingly complex. We should, however, ensure that we are still
in a position where we are able to control technology. It will be all too easy
to suddenly discover that technology is controlling us. By then it might be
too late. So, it’s very important to be suspicious of the benefits that
computers will bring and to make sure that we never become totally
dependent on a completely technological world.
Notes: 1здесь: сложный; 2выгода, польза; 3вблизи; 4при условии, если;
5
бедствие, катастрофа; 6неизбежность
Tasks on the section:
1) On the basis of the texts in this section make a report on new
information technology.
27
2) Indicate the fields where concepts, methods of coding theory and
information theory are used.
3) The prospects for our century to be wired, networked and global are
quite alarming. Do you agree or not? Express your opinion.
4) How do you appreciate the possibility to be dependent on computers?
Why is it necessary to be suspicious of the benefits that computers
might bring to us?
UNIT 3
DATA
(computing)
3.1 Data
Read and translate the text:
Data is information before it has been given any context, structure and
meaning. An example would be; 03091989. At first, this has no meaning,
but if we put it into context, such as 03/09/1989, we suddenly see that it is a
date format. But this still has no meaning, so if we say; 03/09/1989 - the
date of birth, we have successfully transformed 03091989 into a more
understandable format.
In computer science theory there is a clear distinction between data
and information, where data is a measurement1 that can be disorganized
and when the data becomes organized it becomes information. A large class
of practically important propositions are measurements or observations3 of
a variable4. Such propositions may comprise numbers, words, or images.
Raw data5 are numbers, characters, images or other outputs from
devices to convert physical quantities into symbols, in a very broad sense.
Such data are typically further processed by a human or input into a
computer, stored and processed there, or transmitted (output) to another
human or computer. Raw data is a relative term; data processing commonly
occurs by stages, and the “processed data” from one stage may be
considered the “raw data” of the next.
Mechanical computing devices are classified according to the means
by which they represent data. An analog computer represents a datum as a
voltage, distance, position, or other physical quantity. A digital computer
28
represents a datum as a sequence of symbols drawn from a fixed alphabet.
The most common digital computers use a binary alphabet, that is, an
alphabet of two characters, typically denoted “0” and “1”. More familiar
representations, such as numbers or letters, are then constructed from the
binary alphabet.
Notes: 1измерение; 2задача, проблема; 3наблюдения, результаты
научных наблюдений; 4переменная; 5необработанные данные
Questions to the text:
1) Is information a synonym for data?
2) What is a distinction between data and information?
3) What data are considered as raw data?
4) How is a datum represented in computing devices?
5) Name the main categories of mechanical computing devices and state the
difference in their operation.
Give a short (6-8 sentences) summary of the text.
3.2 Data Structure
Read and translate the text:
In the field of computer science, a data structure is a way of storing
data in a computer so that it can be used efficiently. Often a carefully
chosen data structure will allow the most efficient algorithm to be used.
The choice of the data structure often begins from the choice of an abstract
data structure. A well-designed data structure allows a variety of critical
operations to be performed, using as few resources, both execution time
and memory space, as possible. Data structures are implemented using the
data types, references1 and operations on them provided by a programming
language.
Different kinds of data structures are suited to different kinds of
applications, and some are highly specialized to certain tasks. For example,
B-trees2 are particularly well-suited for implementation3 of databases, while
routing tables rely on networks of machines to function.
29
A binary tree, a simple type of branching linked data structure
In the design of many types of programs, the choice of data structures
is a primary design consideration, as experience in building large systems
has shown that the difficulty of implementation and the quality and
performance of the final result depends heavily on choosing the best data
structure. After the data structures are chosen, the algorithms to be used
often become relatively obvious. Sometimes things work in the opposite
direction - data structures are chosen because certain key tasks have
algorithms that work best with particular data structures. In either case, the
choice of appropriate data structures is crucial.
Since data structures are so crucial to professional programmes, many
of them enjoy extensive support in standard libraries of modern
programming languages and environments, such as C++'s Standard
Template Library4, the Java Collections Framework5 and the Microsoft
NET Framework.
The fundamental building blocks of most data structures are arrays6,
records, discriminated unions7, and references. For example, the nullable
reference, a reference which can be null, is a combination of references and
discriminated unions, and the simplest linked data structure, the linked list,
is built from records and nullable references.
There is some debate about whether data structures represent
implementations or interfaces. How they are seen may be a matter of
perspective. A data structure can be viewed as an interface between two
functions or as an implementation of methods to access storage that is
organized according to the associated data type.
Notes: 1ссылки; 2двоичная древовидная схема; 3реализация, внедрение,
ввод в действие; 4библиотека стандартных шаблонов; 5база, основа,
30
структура,
конструкция;
объединение (типов данных)
6
матрица,
таблица;
7
размеченное
Questions and tasks to the text:
1) Define the notion: data structure, binary tree.
2) What data structures are there in programming?
3) Does the design of programs depend on the kind of data structure?
And how?
4) What unsolved problems concerning data structure exist in modern
programming?
Give a short (6-8 sentences) summary of the text.
3.3 (1) Data Compression
Read and translate the text:
In computer science and information theory, data compression or
source coding is the process of encoding information using fewer bits (or
other information-bearing units) than an unencoded representation would
use through use of specific encoding schemes. For example, this article
could be encoded with fewer bits if one were to accept the convention that
the word “compression” be encoded as “comp”. One popular instance of
compression with which many computer users are familiar is the ZIP file1
format, which, as well as providing compression, acts as an archiver,
storing many files in a single output file.
As with any communication, compressed data communication only
works when both the sender and receiver of the information understand the
encoding scheme. For example, this text makes sense only if the receiver
understands that it is intended to be interpreted as characters representing
the English language. Similarly, compressed data can only be understood if
the decoding method is known by the receiver.
Compression is useful because it helps to reduce the consumption2 of
expensive resources, such as hard disk space or transmission bandwidth3.
Compressed data must be decompressed to be viewed (or heard), and this
extra processing may be harmful, to some applications. For instance, a
compression scheme for video may require expensive hardware for the
video to be decompressed fast enough to be viewed as it's being
31
decompressed (the option of decompressing the video in full before
watching it may be inconvenient, and requires storage space for the
decompressed video). The design of data compression schemes therefore
involves trade-offs among various factors, including the degree of
compression, the amount of distortion introduced, and the computational
resources required to compress and uncompress the data.
There are two kinds of compression: lossless data compression and
lossy data compression.
Notes: 1самый распространенный стандарт сжатия файлов и формат
архивов на FTP-серверах; 2потребление, затрата, расход; 3полоса
пропускания (в системах связи - разность между максимальной и
минимальной частотой в заданном диапазоне), пропускная
способность
Questions and tasks to the text:
1)
2)
3)
4)
5)
How does data compression occur?
What examples of data compression are you familiar with?
In what cases does compressed data communication work?
Name some advantages of the process of data compression.
What kinds of data compression are there?
Sum up what you have learned about data compression.
3.3 (2) Lossless Data Compression and Lossy Data Compression
Read and translate the text:
Lossless compression algorithms usually exploit statistical redundancy1
in such a way as to represent the sender’s data more concisely2, but
nevertheless perfectly. Lossless compression is possible because most realworld data has statistical redundancy. For example, in English text, the
letter “e” is much more common than the letter “z”, and the probability that
the letter “q” will be followed by the letter “z” is very small.
Another kind of compression, called lossy data compression, is
possible if some loss of fidelity3 is acceptable. For example, a person
viewing a picture or television video scene might not notice if some of its
finest details are removed or not represented perfectly (i.e. may not even
notice compression artifacts). Similarly, two clips of audio may be sensed
32
as the same to a listener even though one is missing details found in the
other. Lossy data compression algorithms introduce relatively minor
differences and represent the picture, video, or audio using fewer bits.
Lossless compression schemes are reversible so that the original data
can be reconstructed, while lossy schemes accept some loss of data in order
to achieve higher compression.
However, lossless data compression algorithms will always fail to
compress some files; indeed, any compression algorithm will necessarily
fail to compress any data containing no visible patterns. Attempts to
compress data that has been compressed already will therefore usually
result in an expansion, as will attempts to compress encrypted data.
In practice, lossy data compression will also come to a point where
compressing again does not work, although an extremely lossy algorithm,
which for example always removes the last byte of a file, will always
compress a file up to the point where it is empty.
Lossless data compression is often used to optimize disk space on
office computers, or better use the connection bandwidth in a computer
network. For symbolic data such as spreadsheets text4, executable
programs, etc., losslessness is essential because changing even a single bit
cannot be tolerated (except in some limited cases).
Lossy image compression is used in digital cameras, greatly increasing
their storage capacities while hardly degrading picture quality at all.
Similarly, DVDs use the lossy MPEG-2 codes for video compression.
In lossy audio compression, methods of psychoacoustics5 are used to
remove non-audible (or less audible6) components of the signal.
Compression of human speech is often performed with even more
specialized techniques, so that “speech compression” or “voice coding” is
sometimes distinguished as a separate discipline than “audio compression”.
Different audio and speech compression standards are listed under audio
codes. Voice compression is used in Internet telephony for example, while
audio compression is used for CD ripping and is decoded by audio players.
Notes: 1чрезмерность, избыточность; 2кратко, сжато; 3точность
(воспроизведения),
верность
(передачи
информации);
4
5
крупноформатная
(электронная)
таблица;
психоакустика,
психофизиология слухового восприятия; 6слышный, внятный,
слышимый
33
Questions and tasks to the text:
1) What is data compression?
2) What is the difference between lossless data compression and lossy
data compression?
3) In what cases lossy data compression is possible?
4) What are the advantages and disadvantages of lossless data
compression?
5) What are the advantages and disadvantages of lossy data
compression?
6) What applications does data compression have?
Formulate the main idea of the text in 6-8 sentences.
3.4 Data Transmission
Read and translate the text:
Data transmission is the conveyance of any kind of information from
one space to another. Historically this could be done by courier, a chain of
bonfires or semaphores, and later by Morse code over copper wires.
In recent computer terms, it means sending a stream of bits or bytes
from one location to another using any number of technologies, such as
copper wire, optical fiber, laser, radio, or infra-red light. Practical examples
include moving data from one storage device to another and accessing a
website, which involves data transfer from web servers to a user's browser.
There are two types of data transmission: serial transmission and parallel
transmission. Serial transmission bits are sent over a single wire
individually. While only one bit is sent at a time, high transfer rates are
possible. This can be used over longer distances as a check digit or parity
bit1 can be sent along it easily. In parallel transmission multiple wires are
used and transmit bits simultaneously. Parallel transmission is much faster
than serial transmission as one byte can be sent rather than one bit. This
method is used internally within the computer, for example the internal
buses2 and sometimes externally for such things as printers. However this
method of transmission is only available over short distances as the signal
34
will degrade and become unreadable, as there is more interference3 between
many wires than between one.
Another important characteristic of data transmitting is
synchronisation, or time paring. Asynchronous transmission uses start and
stop bits to signify the beginning and end of a transmission. The extra 1 or
0 at the start and end of the transmission tells the receiver first that a
character is coming and secondly that the character has ended. This method
of transmission is used when data is sent intermittently4 as opposed to in a
solid stream. In the previous example the start and stop bits are in bold. The
start and stop bits must be of opposite polarity. This allows the receiver to
recognize when the second packet of information is being sent.
Synchronous transmission uses no start and stop bits but instead
synchronizes transmission speeds at both the receiving and sending end of
the transmission using clock signals5 built into each component. A
continual stream of data is then sent between the two nodes6. Due to there
being no start and stop bits the data transfer rate is quicker although more
errors will occur, as the clocks will eventually get out of sync, and the
receiving device would have the wrong time that had been agreed in
protocol (computing) for sending/receiving data, so some bytes could
become corrupted (by losing bits). Ways to get around this problem include
resynchronization of the clocks and use of check digits to ensure the byte is
correctly interpreted and received.
A protocol is an agreed-upon format for transmitting data between two
devices e.g.: computer and printer. All communications between devices
require that the devices agree on the format of the data. The set of rules
defining a format is called a protocol.
Handshaking7 is the process by which two devices initiate
communication. Handshaking begins when one device sends a message to
another device indicating that it wants to establish a communication
channel. The two devices then send several messages back and forth that
enable them to agree on a communications protocol. Handshaking must
occur before data transmission as it allows the protocol to be agreed.
Notes: 1контрольный (двоичный) разряд чётности; 2магистральная
шина, магистраль; 3взаимное влияние; интерференция; взаимные
помехи; 4толчками, скачками; 5тактовый сигнал, или синхросигнал сигнал, использующийся для согласования операций одной или более
35
цифровых схем; 6узел (в сетях - точка присоединения к сети,
устройство, подключенное к сети); 7установление взаимодействия
Questions and tasks to the text:
1) What does data transmission mean in computer terms?
2) Name types of data transmission.
3) What are the main principles of serial transmission (parallel
transmission, asynchronous transmission, and synchronous
transmission)?
4) What is data transmission protocol?
5) What is handshaking in data transmission?
Give a summary of the text.
3.5 Metadata
Read and translate the text:
The simplest definition of metadata is that it is data about data - more
specifically information (data) about a particular content (data).
An item1 of metadata may describe an individual datum or a collection
of data. For example, in the context of a library, where the data is the
content of the titles stocked, metadata about a title might typically include a
description of the content, the author, the publication date and the physical
location. In the context of a camera, where the data is the photographic
image, metadata might typically include the date the photograph was taken
and details of the camera settings. In the context of an information system,
where the data is the content of the computer files, metadata about an
individual data item might typically include the name of the field and its
length. Metadata about a collection of data items, a computer file, might
typically include the name of the file, the type of file and the name of the
data administrator.
Usually it is not possible to distinguish between (raw) data and metadata
because: something can be data and metadata at the same time; the headline
of an article is both its title (metadata) and part of its text (data). Data and
metadata can change their roles. A poem, as such, would be regarded as
data, but if there were a song that used it as lyrics, the whole poem could be
36
attached to an audio file of the song as metadata. Thus, the labeling
depends on the point of view.
It is possible to create meta-meta-...-metadata. Since, according to the
common definition, metadata itself is data, it is possible to create metadata
about metadata, metadata about metadata about metadata and so on.
Though at first this may seem useless, it can be essential to archive
metadata about metadata, for example to keep track of where the metadata
came from when merging2 two documents.
Metadata has many different applications. Metadata is used to speed up
and enrich searching for resources. In general, search queries using
metadata can save users from performing more complex filter operations
manually. It is now common for web browsers (with the notable exception
of Mozilla Firefox), P2P applications and media management software to
automatically download and locally cache 3 metadata, to improve the speed
at which files can be accessed and searched.
Metadata provide additional information to users of the data it describes.
This information may be descriptive or algorithmic.
Metadata helps to bridge the semantic gap. By telling a computer how
data items are related and how these relations can be evaluated
automatically, it becomes possible to process even more complex filter and
search operations. For example, if a search engine understands that “Van
Gogh” was a “Dutch painter”, it can answer a search query on “Dutch
painters” with a link to a web page about Vincent Van Gogh, although the
exact words “Dutch painters” never occur on that page. This approach,
called knowledge representation, is of special interest to the semantic web
and artificial intelligence.
Certain metadata is designed to optimize lossy compression algorithms.
For example, if a video has metadata that allows a computer to tell
foreground4 from background, the latter can be compressed more
aggressively to achieve a higher compression rate.
Some metadata is intended to enable variable content presentation. For
example, if a picture has metadata that indicates the most important region the one where there is a person - an image viewer on a small screen, such as
on a mobile phone's, can narrow the picture to that region and thus show
the user the most interesting details. A similar kind of metadata is intended
to allow blind people to access diagrams and pictures, by converting them
for special output devices or reading their description using text-to-speech
software.
37
Other descriptive metadata can be used to automate workflows. For
example, if a “smart” software tool knows content and structure of data, it
can convert it automatically and pass it to another “smart” tool as input. As
a result, users save the many copy-and-paste operations required when
analyzing data with “dumb”5 tools.
Metadata is becoming an increasingly important part of electronic
discovery.
Metadata has become important on the World Wide Web because of the
need to find useful information from the mass of information available.
Manually-created metadata adds value because it ensures consistency. If a
web page about a certain topic contains a word or phrase, then all web
pages about that topic should contain that same word or phrase.
1
2
Notes:
элемент,
единица;
слияние,
объединение;
³кэш
(быстродействующая
буферная
память
большой
ёмкости,
используемая для хранения копии областей оперативной памяти с
4
наиболее
частым
доступом);
самое
важное
место,
5
(высоко)приоритетный; неслышный, заглушенный
Questions and tasks to the text:
1) Define the notion metadata.
2) What forms metadata?
3) What applications do metadata have?
4) What are the advantages of using metadata?
Give a short (7-9 sentences), either written or oral, summary of the text.
3.6 DBMS (Database Management System)
Read the text without consulting the dictionary and give a short (8-9
sentences), either written or oral, summary of it:
A DBMS1 is a complex set of software programmes that controls the
organization, storage and retrieval of data in a database. A DBMS includes:
a modeling language to define the schema (relational model)2 of each
database hosted in the DBMS, according to the DBMS data model.
The three most common organizations are the hierarchical, network
and relational models. A database management system may provide one,
38
two or all three methods. Inverted lists3 and other methods are also used.
The most suitable structure depends on the application and on the
transaction rate and the number of inquiries4 that will be made. Many
DBMSs also support the Open Database Connectivity 5 API6 that supports a
standard way for programmers to access the DBMS.
It also controls the security of the database. Data security prevents
unauthorised users from viewing or updating the database. Using
passwords, users are allowed access to the entire database or subsets of it
called subschemas. For example, an employee database can contain all the
data about an individual employee, but one group of users may be
authorized to view only payroll data7, while others are allowed access to
only work history and medical data.
It also maintains the integrity8 of the data in the database. The DBMS
can maintain the integrity of the database by not allowing more than one
user to update the same record at the same time. The DBMS can help
prevent duplicate records via unique index constraints9; for example, no
two customers with the same customer numbers (key fields) can be entered
into the database.
The DBMS accepts requests for data from the application programme
and instructs the operating system to transfer the appropriate data.
When a DBMS is used, information systems can be changed much
more easily as the organization's information requirements change. New
categories of data can be added to the database without disruption10 to the
existing system.
Organizations may use one kind of DBMS for daily transaction
processing and then move the detail onto another computer that uses
another DBMS better suited for random inquiries and analysis. Overall
systems design decisions are performed by data administrators and systems
analysts. Detailed database design is performed by database administrators.
Database servers are specially designed computers that hold the actual
databases and run only the DBMS and related software. Database servers
are usually multiprocessor computers, with RAID disk arrays11 used for
stable storage. Connected to one or more servers via a high-speed channel,
hardware database accelerators are also used in large volume transaction
processing environments.
DBMSs are found at the heart of most database applications.
39
Notes: 1(сокр. от database management system) система управления
базами данных; 2реляционная модель, модель структуры БД,
построенная на понятии отношения, где отношение - двумерная
таблица, предназначенная для упорядоченного хранения данных;
3
инвертированный список (список записей, имеющих определенное
значение вторичного ключа); 4запрос; 5открытый интерфейс доступа к
базам данных программного интерфейса приложения; 6(сокр. от
Application Platform Interface) интерфейс прикладных базовых систем;
7
сведения о платежной ведомости; 8целостность, сохранность;
9
10
ограничение, ограничивающее условие;
подрыв; 11(сокр.от
Redundant Array of Inexpensive [or Independent] Disks) дисковый
массив (матрица), избыточный массив недорогих дисков
Tasks on the section:
On the basis of the texts in this section make a report on: data structure
in modern programming; methods of data compression; new methods of
data transmission.
UNIT 4
NETWORKING
4.1 The Idea and the Definition of Networking
Read and translate the text:
The idea of networking is probably as old as telecommunications itself.
Consider people living in the Stone Age, when drums may have been used
to transmit messages between individuals. Suppose caveman1 A wants to
invite caveman B over for a game of hurling rocks2 at each other, but they
live too far apart for B to hear A banging his drum. What are A's options?
He could 1) walk over to B's place, 2) get a bigger drum, or 3) ask C, who
lives halfway between them, to forward the message. The last option is
called networking.
Of course, we have come a long way from the primitive pursuits3 and
devices of our forebears4. Nowadays, we have computers talk to each other
over vast assemblages of wires, fiber optics, microwaves, and the like, to
make an appointment for Saturday's football match.
A network itself can be defined as a collection of hosts that are able to
communicate with each other, often by relying on the services of a number
40
of dedicated hosts that relay data between the participants. Hosts are often
computers, but need not be; one can also think of X terminals5 or intelligent
printers as hosts. Small agglomerations of hosts are also called sites.
Computer networks differ in their design. The two types of high-level
network design are called client-server and peer-to-peer. Client-server
networks feature centralized server computers that store email, Web pages,
files and/or applications. On a peer-to-peer network, conversely, all
computers tend to support the same functions. Client-server networks are
much more common in business and peer-to-peer networks are much more
common in homes.
Communication is impossible without some sort of language or code. In
computer networks, these languages are collectively referred to as
protocols. These are not written protocols, but rather highly formalized
codes of behavior, for instance, like when heads of state meet. In a very
similar fashion, the protocols used in computer networks are nothing but
very strict rules for the exchange of messages between two or more hosts.
There are a few types of networks in use now. Local Area Networks
(LANs)6 and Wide Area Networks (WANs)7, such as the Internet, rely on
TCP/IP8 as the most popular protocols. However, some other kinds of
protocols, such as IPX9 for the Novell NetWare10 environment, exist too.
All these protocols are networking protocols and are used to carry data
between host computers.
Notes: 1пещерный человек; 2бросать камни; 3ежедневные занятия;
4
предки; 5компьютерный терминал, предназначенный прежде всего
для ввода-вывода данных пользователем, в то время как сама
обработка производится на сервере, с которым терминал объединен в
сеть; относительно низкая стоимость сделала их популярными в 1990е г.г.; 6Локальная вычислительная сеть, ЛВС; 7Глобальная
вычислительная сеть, ГВС; 8transfer control protocol, протокол,
контролирующий передачу данных; Internet protocol, протокол сети
Интернет; 9Internetwork Packet Exchange, протокол сетевого уровня,
обеспечивающий связь между NetWare-серверами и конечными
станциями; 10закрытая сетевая операционная система с набором
сетевых протоколов, которые используются в этой системе для
взаимодействия с компьютерами-клиентами, подключёнными к сети;
создана американской компанией Novell.
41
Questions to the text:
1) How were messages communicated in Stone Age?
2) What is the main purpose of any network?
3) How technically can computers be networked?
4) What basis are networks classified on?
5) What classifications of networks are there?
6) What are the typical designs of computer networks?
7) Which network design (client-server or peer-to-peer) is hierarchical?
Why?
8) What is necessary for communication to take place?
9) What is net protocol similar to? How?
10) What are the most often used protocols? Why are they?
On the basis of the text define the following terms: 1) network; 2) host;
3) site; 4) LAN; 5) WAN; 6) protocol
4.2 Topology in Network Design
Read and translate the text:
In networking, the term “topology” refers to the layout of connected
devices on a network. One can think of a topology as a network's virtual
shape or structure. This shape does not necessarily correspond to the actual
physical layout of the devices on the network. For example, the computers
on a home LAN may be arranged in a circle in a family room, but it would
be highly unlikely to find an actual ring topology there.
Network topologies are categorized into the following basic types:
•
bus1
•
ring
•
star
•
tree
•
mesh2
42
More complex networks can be built as hybrids of two or more of the
above basic topologies.
▪
Bus Topology
Bus networks (not to be confused with the system bus of a computer)
use a common backbone to connect all devices. A single cable, the
backbone, functions as a shared communication medium that devices attach
or tap into with an interface connector. A device wanting to communicate
with another device on the network sends a broadcast message onto the
wire that all other devices see, but only the intended recipient actually
accepts and processes the message.
Ethernet3 bus topologies are relatively easy to install and don't require
much cabling compared to the alternatives. However, bus networks work
best with a limited number of devices. If more than a few dozen computers
are added to a network bus, performance problems are likely to result. In
addition, if the backbone cable fails, the entire network effectively becomes
unusable.
▪
Ring Topology
In a ring network, every device has exactly two neighbors for
communication purposes. All messages travel through a ring in the same
direction (either “clockwise” or “counterclockwise”). A failure in any cable
or device breaks the loop and can take down the entire network. To
implement a ring network, one typically uses FDDI4, SONET5, or Token
Ring6 technology. Ring topologies are found in some office buildings or
school campuses.
▪
Star Topology
43
Many home networks use the star topology. A star network features a
central connection point called a “hub” that may be a hub7, switch8 or
router9. Devices typically connect to the hub with Unshielded Twisted Pair
(UTP10) Ethernet.
Compared to the bus topology, a star network generally requires more
cable, but a failure in any star network cable will only take down one
computer's network access and not the entire LAN. (If the hub fails,
however, the entire network also fails.)
▪
Tree Topology
Tree topologies integrate multiple star topologies together onto a bus. In
its simplest form, only hub devices connect directly to the tree bus and each
hub functions as the “root” of a tree of devices. This bus/star hybrid
approach supports future expandability of the network much better than a
bus (limited in the number of devices due to the broadcast traffic it
generates) or a star (limited by the number of hub connection points) alone.
▪
Mesh Topology
Mesh topologies involve the concept of routes. Unlike each of the
previous topologies, messages sent on a mesh network can take any of
several possible paths from source to destination. (Recall that even in a
ring, although two cable paths exist, messages can only travel in one
direction.) Some WANs, most notably the Internet, employ mesh routing.
A mesh network in which every device connects to every other is called
a full mesh. As shown in the illustration below, partial mesh networks also
exist in which some devices connect only indirectly to others.
Notes: 1магистральная шина, магистраль; 2ячейка сети, петля; 3эзернет,
(от лат. aether - эфир), пакетная технология компьютерных сетей,
ставшая самой распространённой технологией ЛВС в середине 1990-х
г.г.; 4Fiber-Distributed Data Interface, распределённый волоконный
интерфейс данных, стандарт передачи данных в ЛВС на расстоянии до
200 км, основанный на протоколе token ring; 5synchronous optical
networking standard, стандарт синхронизированной оптоволоконной
сети, широко распространенный в США; 6«маркерное кольцо»,
архитектура кольцевой сети с маркерным (эстафетным) доступом;
технология, разработанная компанией IBM; 7сетевой концентратор
или хаб (от англ. hub — центр деятельности), сетевое устройство для
объединения нескольких устройств Ethernet в общий сегмент;
8
коммутатор (свитч); 9маршрутизатор; 10витая пара, вид кабеля связи в
44
виде одной или нескольких пар изолированных проводников,
скрученных между собой (с небольшим числом витков на единицу
длины), для уменьшения взаимных наводок при передаче сигнала, и
покрытых пластиковой оболочкой.
Questions to the text:
1) What is ‘topology’ in networking? How doe it correspond to the
physical layout?
2) What are the basic topologies of networks?
3) What are the principles of their architectural design?
4) What are the advantages and disadvantages of different topologies?
5) Where can they be used?
Give a short (7-9 sentences), either written or oral, summary of the text.
4.3 Area Networks
Read and translate the text:
One way to categorize the different types of computer network designs
is by their scope or scale. For historical reasons, the networking industry
refers to nearly every type of design as some kind of area network.
Common examples of area network types are:
•
LAN - Local Area Network
•
WLAN - Wireless Local Area Network
•
WAN - Wide Area Network
•
MAN - Metropolitan Area Network
•
SAN - Storage Area Network, System Area Network, Server Area
Network, or sometimes Small Area Network
•
CAN - Campus Area Network, Controller Area Network, or
sometimes Cluster Area Network
•
PAN - Personal Area Network
•
DAN - Desk Area Network
LAN and WAN were the original categories of area networks, while the
others have gradually emerged over many years of technology evolution.
▪
LAN - Local Area Network
45
LAN’s basic characteristic is connection over a relatively short distance.
A networked office building, school, or home usually contains a single
LAN, though sometimes one building will contain a few small LANs
(perhaps one per room), and occasionally a LAN will span a group of
nearby buildings. In TCP/IP networking, a LAN is often but not always
implemented as a single IP subnet.
In addition to operating in a limited space, LANs are also typically
owned, controlled, and managed by a single person or organization. They
also tend to use certain connectivity technologies, primarily Ethernet and
Token Ring.
▪
WAN - Wide Area Network
As the term implies, a WAN spans a large physical distance. The
Internet is the largest WAN, spanning the Earth.
A WAN is a geographically-dispersed collection of LANs. A network
device called a router connects LANs to a WAN. In IP networking, the
router maintains both a LAN address and a WAN address.
A WAN differs from a LAN in several important ways. Most WANs
(like the Internet) are not owned by any one organization but rather exist
under collective or distributed ownership and management. WANs tend to
use technology like Frame Relay1 and X.252 for connectivity over the
longer distances.
▪
LAN, WAN and Home Networking
Residences typically employ one LAN and connect to the Internet WAN
via an Internet Service Provider (ISP) using a broadband modem. The ISP
provides a WAN IP address to the modem, and all of the computers on the
home network use LAN (so-called private) IP addresses. All computers on
the home LAN can communicate directly with each other but must go
through a central gateway, typically a broadband router3, to reach the ISP.
▪
Other Types of Area Networks
While LAN and WAN are by far the most popular network types
mentioned, you may also commonly see references to these others:
•
Wireless Local Area Network - a LAN based on WiFi4 wireless
network technology.
•
Metropolitan Area Network - a network spanning a physical area
larger than a LAN but smaller than a WAN, such as a city. A MAN is
46
typically owned an operated by a single entity such as a government body
or large corporation.
•
Campus Area Network - a network spanning multiple LANs but
smaller than a MAN, such as on a university or local business campus.
•
Storage Area Network - connects servers to data storage devices
through a technology like Fibre Channel.
•
System Area Network - links high-performance computers with
high-speed connections in a cluster configuration, also known as Cluster5
Area Network.
Notes: 1«ретрансляция кадров», FR, протокол канального уровня,
изначально ориентированный на физические линии с низкой частотой
ошибок; 2протокол, рассчитанный на линии с достаточно высокой
3
частотой
ошибок,
напр.
телефонные;
широкополосный
4
маршрутизатор;
стандарт оборудования беспроводных ЛВС,
разработанный консорциумом «Wi-Fi Alliance». Технологию назвали
Wireless-Fidelity (дословно "Беспроводная Надежность") по аналогии с
Hi-Fi; 5кластер, разновидность параллельной или распределенной
системы,
используемой
как
единый,
унифицированный
компьютерный ресурс.
Questions to the text:
1)
2)
3)
4)
What are the basic types of area networks?
What are their principle characteristics?
Where are they used?
What other types of area networks exist?
Summarize the information of the text and comment on the area
networks.
4.4 Connectivity
Read and translate the text:
When networking two computers, the cheapest and simplest way to
connect them is through a point-to-point connection. Crossover cabling,
47
direct cable connection (DCC), or infrared connections are three methods
for building point-to-point home networks:
Direct Cable Connection (DCC) is a feature built into Windows
computers beginning with Windows 95. Direct Cable Connection (DCC) is
only available on Windows computers.
Crossover cabling works best when networking computers running
different operating systems. Crossover cabling also supports the Fast
Ethernet speeds required for a shared home Internet connection.
Mobile computers typically support infrared networking via built-in
infrared ports. Infrared networks run at slow speeds but are extremely
useful for point-to-point file sharing.
Powerline networks use the electrical power lines of a home instead of
Ethernet cables to transmit network data. Phoneline networks utilize
telephone lines run between different rooms of a home. Both powerline and
phoneline options can be set up by purchasing special kits for that purpose.
▪
Wired Networks
This diagram illustrates several common forms of wiring in computer
networks. In many homes, twisted-pair Ethernet cables are often used to
connect computers. Phone or cable TV lines in turn connect the home LAN
to the Internet Service Provider (ISP). ISPs, larger schools and businesses
often stack their computer equipment in racks (as shown), and they use a
48
mix of different kinds of cable to join this equipment to LANs and to the
Internet. Much of the Internet uses high-speed fiber optic cable to send
traffic long distances underground, but twisted pair and coaxial cable can
also be used for leased lines and in more remote areas.
Ethernet is a physical and data link layer technology for LANs invented
by engineer Robert Metcalfe.
When first widely deployed in the 1980s, Ethernet supported a
maximum theoretical data rate of 10 megabits per second (Mbps). Later,
Fast Ethernet standards increased this maximum data rate to 100 Mbps.
Today, Gigabit Ethernet technology further extends peak performance up to
1000 Mbps.
The run length of individual Ethernet cables is limited to roughly 100
meters, but Ethernet can be bridged to easily network entire schools or
office buildings.
▪
Wireless Networks
This diagram illustrates several common forms of wireless computer
networks. Wi-Fi is the standard technology for building wireless home
networks and other LANs. Businesses and communities also use the same
Wi-Fi technology to set up public hotspots. Next, Bluetooth networks allow
handhelds, cell phones and other other peripheral devices to communicate
49
over short ranges. Finally, cellular technology supports voice
communications over mobile phones.
BlueTooth is a specification for the use of low-power radio
communications to wirelessly link phones, computers and other network
devices over short distances. The name "Bluetooth" is borrowed from
Harald Bluetooth, a king in Denmark more than 1,000 years ago.
Bluetooth technology was designed primarily to support simple wireless
networking of personal consumer devices and peripherals, including cell
phones, PDAs1, and wireless headsets. Wireless signals transmitted with
Bluetooth cover short distances, typically up to 30 feet (10 meters).
Bluetooth devices generally communicate at less than 1 Mbps.
Bluetooth networks feature a dynamic topology called a piconet or
PAN2. Piconets contain a minimum of two and a maximum of eight
Bluetooth peer devices.
Compared to Wi-Fi, Bluetooth networking is much slower, a bit more
limited in range, and supports many fewer devices.
A hotspot is any location where Wi-Fi network access (usually Internet
access) is made publicly available. You can often find hotspots in airports,
hotels, coffee shops, and other places where business people tend to
congregate. Hotspots are considered a valuable productivity tool for
business travelers and other frequent users of network services.
Technically speaking, hotspots consist of one or several wireless access
points (AP) installed inside buildings and/or adjoining outdoor areas. These
APs are typically networked to printers and/or a shared high-speed Internet
connection. Some hotspots require special application software be installed
on the Wi-Fi client, primarily for billing and security purposes, but others
require no configuration other than knowledge of the network name.
Wireless service providers generally own and maintain hotspots.
Hobbyists sometimes setup hotspots as well, often for non-profit
purposes. The majority of hotspots require payment of hourly, daily,
monthly, or other subscription fees. Hotspot providers strive to make
connecting Wi-Fi clients as simple and secure as possible. However, being
public, hotspots generally provide less secure Internet connections than do
other wireless business networks.
Notes: 1КПК, Personal Digital Assistant, «личный цифровой секретарь»;
пиконет, компьютерная сеть, использующая протоколы технологии
Bluetooth, для объединения нескольких подчиненных устройств
2
50
(slaves) с главным (master); personal area network, используемая для
объединения стационарного компьютера или ноутбука с телефоном
и/или КПК одного человека и/или выхода в Интернет.
Questions to the text:
1)
2)
3)
4)
5)
How are computers in the network connected?
What are the main principles of wired networking?
What are the advantages and disadvantages of wired networks?
Where are they typically used?
What are the main principles of wireless networking?
On the basis of the text compare the wired and wireless networks. What
problems arise in case of wired/wireless connections?
4.5 Network File Sharing
Read and translate the text:
Computer networks allow you to share files with friends, family,
coworkers and customers. Before the Internet and home networks became
popular, files were often shared using floppy disks. Nowadays, some
people still use CD-ROM/DVD-ROM disks and USB keys for transferring
their photos and videos, but networks give you more flexible options.
Network file sharing is the process of copying files from one computer
to another using a live network connection. Different available methods and
networking technologies to share files are:
▪
File Sharing With Microsoft Windows
Microsoft Windows (and other personal computer operating systems)
contain built-in features for file sharing. For example, Windows file folders
can be shared across a LAN or the Internet using the Explorer interface and
network drive mappings. You can also set up security access restrictions
that control who can obtain the shared files.
▪
FTP File Transfers
File Transfer Protocol (FTP) is an older but still popular method to share
files on the Internet. A central computer called the FTP server holds all the
51
files to be shared, while remote computers running FTP client software can
log in to the server to obtain copies.
All modern computer operating systems contain built-in FTP client
software, and popular Web browsers like Internet Explorer can also be
configured to run as FTP clients. Alternative FTP client programs are also
available for free download on the Internet. As with Windows file sharing,
security access options can be set on the FTP server requiring clients to
supply a valid login name and password.
▪
P2P - Peer to Peer File Sharing
Peer to peer (P2P) file sharing an extremely popular method for
swapping large files on the Internet, particularly music and videos. Unlike
FTP, most P2P file sharing systems do not use any central servers but
instead allow all computers on the network to function both as a client and
a server. Numerous free P2P software programs exist each with their own
technical advantages and loyal community following.
▪
Email
For decades, files can be transferred from person to person over a
network using email software. Emails can travel across the Internet or
within a company intranet. Like FTP systems, email systems use a
client/server model. The sender and receiver may use different email
software programs, but the sender must know the recipient's email address,
and that address must be configured to allow the incoming mail.
Email systems are designed for transferring small amounts of data and
generally limit the size of individual files that can be shared.
▪
Online Sharing Services
Finally, numerous Web sites built for community file sharing exist on
the Internet. Members post or upload their files to the site using a Web
browser, and others can then download copies of these files using their
browser. Some community file sharing sites charge member fees, while
others are free (advertising supported).
Questions to the text:
1) What is file sharing intended for?
2) Which were/are the usual ways to share files?
52
3) How many file-sharing methods and technologies are enumerated
above? What are they? How and for what are they commonly used?
Which are the ones you use?
Write a brief story (about 120-150 words) on your personal experience of
file sharing.
4.6 Planning and Building the Local Area Network
Read and translate the text:
Before purchasing and installing equipment, determine your needs. The
location of your computer(s), printer(s) and other devices you want to
connect can affect your network design. Some systems may already contain
built-in networking capability while others may not.
Those devices that need network capability added probably support only
certain kinds of network gear. Take care to buy compatible gear. If you
desire shared Internet access, be sure to factor this into your design. Other
important factors in network design include reach and speed. Finally,
consider both present and future needs in your plan. How many computers
will your network have in the next year or two? A network with just two
computers can involve a very different design than a network with five, for
example.
The home networker can choose from either wireless or wired designs.
Wireless networks provide more mobility to a person in and around their
home, and they make especially good sense for laptop networking.
Networks with wires or cables, on the other hand, usually cost less than
wireless, may perform faster and more reliably, and make good sense for
desktop networking. Choosing between wired and wireless options can be
difficult, but making an informed decision here can save money and
increase one's overall satisfaction with their home network.
In building networks the five key areas are: ease of installation, total
cost, reliability, performance, and security.
▪
Installation
Ethernet cables must be run from each computer to another computer or
to the central device. It can be time-consuming and difficult to run cables
under the floor or through walls, especially when computers sit in different
53
rooms. Some newer homes are pre-wired, greatly simplifying the cabling
process and minimizing unsightly cable runs.
The correct cabling configuration for a wired LAN varies depending on
the mix of devices, the type of Internet connection, and whether internal or
external modems are used. However, none of these options pose any more
difficulty than, for example, wiring a home theater system.
After hardware installation, the remaining steps in configuring either
wired or wireless LANs do not differ much as both rely on standard
Internet Protocol and network operating system configuration options.
▪
Cost
Ethernet cables, hubs and switches are very inexpensive. Some
connection sharing software packages are free; some cost a nominal fee.
Broadband routers cost more, but these are optional components of a wired
LAN, and their higher cost is offset by the benefit of easier installation and
built-in security features.
▪
Reliability
Ethernet cables, hubs and switches are extremely reliable, mainly
because manufacturers have been continually improving Ethernet
technology over several decades. Loose cables likely remain the single
most common and annoying source of failure in a wired network. When
installing a wired LAN or moving any of the components later, be sure to
carefully check the cable connections.
Broadband routers have also suffered from some reliability problems in
the past. Unlike other Ethernet gear, these products are relatively new,
multi-function devices. Broadband routers have matured over the past
several years and their reliability has improved greatly.
▪
Performance
Wired LANs offer superior performance. Traditional Ethernet
connections offer only 10 Mbps bandwidth, but 100 Mbps Fast Ethernet
technology costs little more and is readily available. Although 100 Mbps
represents a theoretical maximum performance never really achieved in
practice, Fast Ethernet should be sufficient for home file sharing, gaming,
and high-speed Internet access for many years into the future.
Wired LANs utilizing hubs can suffer performance slowdown if
computers heavily utilize the network simultaneously. Use Ethernet
54
switches instead of hubs to avoid this problem; a switch costs little more
than a hub.
▪
Security
For any wired LAN connected to the Internet, firewalls1 are the primary
security consideration. Wired Ethernet hubs and switches do not support
firewalls. However, firewall software products can be installed on the
computers themselves. Broadband routers offer equivalent firewall
capability built into the device, configurable through its own software.
Notes: 1(меж)сетевой экран или брандмауэр, комплекс аппаратных
и/или программных средств, осуществляющий контроль и
фильтрацию проходящих через него сетевых пакетов на различных
уровнях в соответствии с заданными правилами, основной задачей
которого является защита компьютерных сетей или отдельных узлов
от несанкционированного доступа. Часто называют фильтрами, т.к.
их основная задача - не пропускать (фильтровать) пакеты не
подходящие под критерии, определенные в конфигурации.
Questions to the text:
1) What should you think about when planning a network?
2) How is the decision between a wired and wireless networking taken?
3) What are the main factors to consider?
4) What should be done before the installation stage?
5) What are the ways to minimize the costs of installation?
6) Why is reliability and security so crucial for computer networking?
7) What does network performance depend on?
Make up a plan of the text. Explain what factors should be considered
while planning and building a LAN and why.
Tasks on the section:
1) On the basis of the texts in this section make a report on Networking.
Mention the idea of networking, network designs, topologies, and
connectivity.
2) Recommend a LAN for a home or a business. Think of the factors
you should consider. Explain your choice.
55
CONTENTS
UNIT 1
COMMUNICATION.......................................................................... 3
1.1 Communication .................................................................................................. 3
1. 2 TELEPHONE .................................................................................................... 4
1.2 (1) Telephone...................................................................................................... 4
1.2 (2) Signalling ...................................................................................................... 6
1.2 (3) Instant Messaging ......................................................................................... 7
1.2 (4) IM Benefits ................................................................................................... 8
1.2 (5) Mobile Instant Messaging ............................................................................ 8
1.3 RADIO................................................................................................................ 9
1.3 (1) Radio Network.............................................................................................. 9
1.3 (2) Scientific Theory and Verification ............................................................. 10
1.3 (3) The Hertz Antenna...................................................................................... 12
1.3 (4) Tesla's Work................................................................................................ 12
1.3(5) Tesla Transmitters........................................................................................ 13
1.4 TELEVISION................................................................................................... 14
1.4 (1) Television Network..................................................................................... 14
1.4 (2) The History of Television Network............................................................ 16
1.4 (3) Let’s Put the Vision in Television!............................................................. 17
UNIT 2
INFORMATION .............................................................................. 18
2.1 Information as a Powerful Resource ................................................................ 18
2.2 Information Technology................................................................................... 19
2.3 Information Theory .......................................................................................... 21
2.4 Coding Theory.................................................................................................. 23
2.5 MP3................................................................................................................... 24
2.6 Summing up the 20th Century .......................................................................... 26
2.7 To Depend on Computers – Is it Bad or Not? ................................................. 27
UNIT 3
DATA ............................................................................................... 28
3.1 Data ................................................................................................................... 28
3.2 Data Structure ................................................................................................... 29
3.3 (1) Data Compression....................................................................................... 31
3.3 (2) Lossless Data Compression and Lossy Data Compression ....................... 32
3.4 Data Transmission ............................................................................................ 34
3.5 Metadata............................................................................................................ 36
3.6 DBMS (Database Management System) ......................................................... 38
UNIT 4
NETWORKING............................................................................... 40
4.1 The Idea and the Definition of Networking..................................................... 40
4.2 Topology in Network Design........................................................................... 42
4.3 Area Networks.................................................................................................. 45
4.4 Connectivity...................................................................................................... 47
4.5 Network File Sharing ....................................................................................... 51
4.6 Planning and Building the Local Area Network.............................................. 53
56
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