The Internet is a
vast network of computers that connects
many of the world's businesses, institutions, and
individuals. The Internet, which is short for interconnected network
of networks, links tens of thousands of smaller computer
networks. It enables users of computers and other networked devices
throughout the world to send and receive messages, share
information in a variety of forms, and even play computer games with
people thousands of miles or kilometers away. Computers
linked to the Internet range from simple and inexpensive personal
computers, often called PC's, to huge mainframe computers
used by government institutions, educational institutions, and
businesses. Other devices linked to the Internet include
sophisticated telephones and televisions.
and other devices require special hardware and software to connect to
the Internet. Necessary hardware
includes a modem or an adapter. A modem is a device that
translates a computer's digital (numerical) information into
signals that can be transmitted over telephone lines, over
cable, or through the air as wireless communications (see Modem).
An adapter, also called a network interface card, links a
computer to a high-speed communication system designed to carry
data in digital form. Adapters are often called modems,
though they are not true modems. Required software includes a
program that allows the transmission and receipt of
messages. Many computers and computing devices come with modems and
Internet, often called simply the Net,
began as a collection of text-only documents intended for
scientists, universities, and some parts of government. But the
development and rapid growth of the World Wide Web (also
known as the Web) transformed the presentation of information on
the Net. The Web is a worldwide system of interconnected
computer files linked to one another on the Net. It enables the use
of multimedia—which includes photographs, moving pictures,
and sound as well as text. Multimedia presentations on the
Web approach the visual quality of television and the audio
(sound) quality of recorded music.
Web consists of millions of Web sites, collections of information at
specific electronic addresses. Web sites
in turn contain Web pages that hold multimedia or text-only
information. Web sites and their pages reside in computers connected
to the Internet.
Uses of the
tens of millions of people and businesses use the Net and the Web
daily. The major uses include communications, research,
publishing, business transactions, and push technology, which employs
the Web for the broadcast of video and audio programming.
Probably the most popular use of the Internet and the Web is
sending and receiving e-mail (electronic mail). The number of
e-mail messages sent each year far exceeds the number of
pieces of traditional mail carried by the world's postal systems.
companies, and institutions have e-mail addresses that enable
the sending and receipt of mail, just as a street address or
post office box provides directions for traditional mail delivery.
Users generally acquire e-mail addresses through an Internet
service provider (ISP) or an online service. Both of these types
of businesses provide access to the Internet. An ISP
maintains its customers' e-mail addresses, routes e-mail and requests
for Internet-based information to and from its users, and
manages high-speed communications lines that quicken the transfer
of data over the Internet. An online service resembles an
ISP, but it provides a wide range of exclusive content in addition
to Internet access. Most ISP's and online services allow
customers to have several different e-mail addresses.
e-mail users attach illustrations, sound files, and even videos to
their e-mails. An e-mail recipient whose computer system
contains the required software can then view and listen to attachments
as well as read the text message. Attachments may include
charts and graphs, and even the text of entire books.
Internet easily enables multiple mailings, the sending of the same
e-mail to many addresses. Businesses advertise products and
services via e-mail. Newsgroups—loose organizations of people
who share a common interest—also use multiple mailings. They
send their members copies of e-mail on the subject of interest.
Members can respond to those e-mails and may introduce new
much e-mail contains financial and other private
information, most e-mail software includes encryption
that convert private e-mail into secret code for
transmission. Similar software decrypts (translates back into readable
the code when it reaches its intended destination.
communicate over the Internet using instant messaging. This
technology notifies a user when a friend or co-worker from a list
created by the user is online. It then enables the two to
communicate through text messages that can be seen by both users
as the messages are typed.
of the Internet resembles a vast library, containing as much
information on every subject as might be held in tens of millions
of books. Information may appear as files consisting only of
text or as multimedia displays.
types of programs called search engines help people sort through the
vast amounts of information on the Internet.
Web users can choose from many search engines available on
Web pages. A search engine allows a user to enter a topic for search,
then finds Web pages that match that topic.
ease with which computers store information, and the speed
with which computer users can access it, the Internet serves as
a popular first stop for many people investigating a
particular topic. A businessperson might search Internet resources for
help in developing sales or product information. Students
can access databases to find material related to homework assignments.
Physicians can use the Net to compare medical treatments and
to review advances in medical science. Scientists can share research
data on the Net.
use the Internet as a medium for presenting the contents of
newspapers, magazines, and books. Because information on the Net
is electronic, the publisher saves the costs of paper,
printing, and distribution. More importantly, the publisher can update
information almost instantly, making it possible to
distribute far more current news than could be provided on paper.
versions of newspapers and magazines often contain more information
than a paper publication could include. Web-based
publications can also present interactive features. For example, a news
story may contain links (interactive connections) to related
stories or background information. If a reader wishes to explore
the linked material, he or she simply clicks on a
highlighted word to connect to a Web page containing that information.
Internet also serves as a distribution system for e-books (electronic
books). An e-book consists of digital files formatted so
that when a reader downloads (transfers) them to a special handheld
device—or to a computer with special software—the words and
pictures appear much as they would on a printed page.
A customer can buy e-books at the publisher's Web site or at
a site owned by a bookstore. Some electronic library sites
include text-only e-books. These e-books can be viewed
without the use of special devices or software.
Many companies use the Internet to carry
out business transactions commonly referred to as
e-commerce. Retailers sell nearly every type of product over the
Users generally pay for such purchases with credit cards.
Software publishers view the Net as a convenient and inexpensive
way to distribute their products. Over the Internet, users
can buy new computer programs, sample programs before purchasing
them, or receive upgrades to programs they already own.
Music publishers sell copies of songs as downloadable digital files.
between companies and consumers are commonly known as B2C
(business to consumer) transactions. Additionally, many
companies use the Internet to engage in B2B (business to business)
transactions. By linking together in a vast network, buyers
and sellers can share information, keep track of inventories,
assess needs, and compare products far more efficiently than
they could using traditional business communications.
Internet has important uses within the financial community. Many banks
and stockbrokers offer their customers software to make and
track investments from their computer. Consumers can use similar
software to pay many types of bills. Individuals can also
file tax returns and pay taxes over the Internet. Economic transactions
over the Internet use encryption technology to protect the
privacy and security of the users.
popular type of Internet business is the online auction. Online
auctions enable people to post descriptions of
items they wish to sell, along with a suggested opening bid.
Visitors to the auction site may place a bid on any posted item.
Consumer auction sites offer almost every imaginable type of
item. But most forbid the sale of dangerous or illegal materials.
Business auction sites, also called trading exchanges, have
captured a large share of B2B transactions. Such sites may, for
example, offer manufacturers the chance to bid on raw
technology, also known as Webcasting or Netcasting, takes
advantage of the ability of the Internet and the Web to deliver
high-quality digital audio or video signals. Push technology
enables producers to distribute their presentations to PC's
and other devices capable of receiving and playing them.
technology programs have no fixed schedules. A producer can
offer audio or video presentations to anyone who subscribes to
them. The user might either download the entire video to his
or her computer for later playback or play it in real time over
the Internet. Real-time play is possible through a
technology called streaming. Many radio stations stream their
in real time so that people throughout the world may listen
over the Web. Many also offer downloads of previous programming.
networks and movie producers often use push technology to promote
their products and to present clips from programs and motion
pictures. Some television producers have created programming
specifically for the Web. Such programs are often called
television news organizations use the Web to post additional stories,
constantly updating the news. They also
offer extended versions of interviews and other features.
Popular offerings include weather reports, global financial information,
sports scores, and breaking news.
Net is a popular showcase
for short independent films. Many independent and amateur
filmmakers create films using digital video cameras, which store
video in digital format suitable for transmission over the
Internet. They can then use special software to edit their films
and to add professional-quality special effects.
uses. Yet another popular feature of the Net is
chat. Using special software, users can gather in electronic "chat
rooms" and send typed messages back and forth, discussing
topics of common interest. The Internet also features many
Web-based games with animation, sound effects, and music.
Game players can challenge others in distant countries to tournaments.
creation of personal Web pages is a particularly popular use of the
Web. Individuals create and maintain these pages. Some
people use such pages to share personal information or to promote
ideas and theories. One type of page, called a Weblog or
blog, is a personal journal of thoughts and ideas for other users
to read. A Weblog may also contain links to an individual's
favorite Web sites. Most ISP's and online services provide
space on a resource computer called a server, or host, for
hosting (storing) Web pages for individuals. Many services include
the use of this space in the subscription price. But some
charge the individual separately for the use of server space.
often place messages on frequently visited Web pages. Links
join these messages electronically to the advertiser's own
Web site. In effect, advertisers can invite Internet users
to view commercials on their computer. Additionally, a user
can supply the advertiser with his or her e-mail address to get
further information, or such incentives as discount coupons.
the Internet works
networks enable computers
to communicate and share information and resources. The
simplest networks consist of a user's computer, known as the client,
and a server. The client makes requests of the server,
which, in turn, provides the requested resources, such as information
or software. The Internet works in much the same way, on a
far vaster scale. To connect to the Net, a user logs on by instructing
his or her computer's communications software to contact the
ISP or online service. To protect the user's security,
this process usually requires a secret password.
was built around telephone connections that were, for the
most part, the same as those used for voice communications. But
the ever-increasing volume of Internet traffic, and the
large size of video and sound files, require faster communications
links. High-speed links, often called broadband connections,
can deliver large amounts of information more quickly than traditional
telephone lines can.
the most common broadband connections
are (1) cable television connections, (2) fiber-optic
telephone lines, (3) ISDN (integrated services digital network) and
DSL (digital subscriber line), and (4) satellite
connections. Cable television connections use the same cables that
television signals to carry Internet traffic. They require
the use of a special cable modem. Fiber-optic telephone lines employ
thin, high-capacity fibers to transmit vast amounts of
information as patterns of light. ISDN and DSL use new technologies
to increase the information-carrying capacity of traditional
copper phone lines. Satellite connections use wireless communications
with orbiting satellites. They enable people to use the
Internet even in locations with no land-based communications lines.
connected to the ISP or online service, the user has several options.
The user's communications software alone may provide access
to such functions as e-mail and newsgroups. Most such software
also includes a simple word processing program that enables a
user to compose, revise, or read messages. A piece of software
known as a browser enables a user to gain access to millions
of Web sites. Each site has a separate electronic address, known
as a uniform resource locator (URL). Many search engines and
other programs throughout the Internet maintain and constantly
update directories of addresses.
are organized into various top level domains (major
categories). In a URL, the top level domain takes the form of a of an
extension of two or more letters, such as .ca for Canada,
.com for commercial, .edu for educational, or .museum for museum.
An organization called The Internet Corporation for Assigned
Names and Numbers (ICANN) coordinates the assignment of top level
domains. In the United States, a domain name includes a top
level domain and a second level domain. In the domain name
for example, worldbook is the second level domain.
an address, or by clicking on a link, a user transmits a
request through the ISP or online service and onto the larger Internet.
When the request arrives at the desired destination, the
server responds by sending the user the requested information. This
information is often in the form of a starting page called a
home page, which often resembles the table of contents of a book
or magazine. From a home page, the user can search for
further information by using links to other pages within the same Web
site or to other Web sites.
browsers include systems for
bookmarking (recording) the addresses of favorite or
frequently visited sites. A user who has bookmarked a site simply clicks
on the appropriate bookmark to visit the site again.
maintain personal Web sites under domain names that include
their own names. Several companies register domain names. Many
ISP's and online services also register domain names for
their customers for an added charge.
files, especially illustration, motion-picture, and sound files, travel
over the Internet in compressed form.
One compression technique stores data that represent a less
precise version of an image or sound than the original file does.
Another technique saves space by removing image or sound
data that are repeated, then merging all the repeated sections together
into a separate file. When the original file is
decompressed, the repeated sections return to their proper places.
about uses of the Internet
Internet and the Web have revealed only a fraction of their potential
as tools for education, research, communications,
news, and entertainment. Most people believe that the
benefits of the Internet far outweigh its challenges. However, some
people have serious concerns over the use of the Internet.
about material. Among concerns over use of the Internet are
doubts about the accuracy and appropriateness of information.
Much information posted on the Internet may be misleading,
inaccurate, or even fraudulent. Many teachers teach their students
how to evaluate the information they find on the Internet
and identify which Web sites are reputable sources.
parents worry about violent or pornographic material available on the
Criminals may lurk in chat rooms, seeking to arrange
face-to-face meetings with unsuspecting victims. Special programs known
as parental control software, also called Internet filters,
can help parents restrict access to sites that may be unsuitable
the United States, the Children's Internet
Protection Act requires the installation of such filters in
public schools and libraries that provide Internet access and
receive federal funding. Schools and libraries that fail to
comply with the act could lose federal aid.
is an important concern for those who use the Internet. Mischievous
known as hackers often try to break into large computer
systems. Some damage databases stored in these systems or attempt
to steal information or electronic funds. Others may seek
access to personal financial information. Many people feel concerned
about the security and confidentiality of credit card
numbers used to make purchases over the Internet. To protect themselves
and their services from unwanted intruders, many ISP's and
online services, corporations, and even individuals erect software
and hardware barriers called firewalls. Such barriers seal
off a server or other computer from intrusion.
itself can become a danger on the Internet. Programs known as viruses,
e-mail bombs, Trojan horses, and worms have spread across
the Internet and can cause damage to data on systems that receive
them. Some of these programs have spread to computers around
the world in a matter of hours. Many companies produce software
designed to protect users from viruses and other such
destructive programs. Most publishers of virus protection software
their programs when new types of viruses are detected.
Customers can often download these updates over the Internet.
The distribution of e-books, digital music,
and digital video poses important legal questions,
particularly because digital files can be so easily pirated—that
is, copied and distributed without permission or payment.
Web users can e-mail copies of e-books and digital recordings anywhere.
Unauthorized Web sites offer pirated e-books, recordings, or
videos. Some Internet companies provide sites where people can
freely share digital copies of music. At first, this sharing
was free, and the traditional music industry claimed that the
practice was illegal. Several music distributors
participated in lawsuits against the companies. As a result, these
have begun to charge customers for downloads and pay fees to
As the Internet and Web have become more popular and powerful, concern
grown about equality of access to their resources. Computers
are costly, as are ISP and online service subscriptions. To ensure
more equal access to the Net, many public libraries and
schools provide Internet-capable computers for individual use. In
many cities around the world, establishments known as
Internet cafes offer people the use of Internet-ready computers for
a fee based on time of use. Such establishments are
especially popular in areas of the world where many people do not have
computers or even telephones.
of the Internet
development. The Internet began to take shape in the late 1960's.
The United States Department of Defense was concerned at the
time about the possibility of devastating nuclear warfare. It
began investigating means of linking computer installations
together so that their ability to communicate might withstand
a war. Through its Advanced Research Projects Agency (ARPA),
the Defense Department initiated ARPANet, a network of university
and military computers.
network's operating protocols
(rules) laid the groundwork for relatively fast and
error-free computer-to-computer communications. Other networks adopted
these protocols, which in turn evolved as new computer and
communications technologies became available.
the 1970's, ARPANet grew at a slow but steady pace. Computers in
other countries began to join the network. Other networks
came into existence as well. These included Unix to Unix Copy (UUCP),
which was established to serve users of the UNIX operating
system, and USENET (user network), a medium for posting text-based
articles on a variety of subjects.
1981, just over 200 computers
were connected to ARPANet. The U.S. military then divided
the network into two organizations—ARPANet and a purely military
network. During the 1980's, ARPANet was absorbed by NSFNET, a
more advanced network developed by the National Science
Foundation, an independent agency of the federal government.
Soon, the collection of networks became known simply as the Internet.
the reasons for the slow growth of the early Internet was the difficulty
of using the network. To access its information, users had
to master complex series of programming commands that required
either memorization or frequent reference to special
World Wide Web. The Internet's breakthrough to mass
popularity occurred in 1991 with the arrival of the World Wide Web.
The Web was developed by Tim Berners-Lee, a British computer
scientist at the European Organization for Nuclear Research (CERN).
One feature that helped popularize the Web was its ability
to deliver multimedia.
programming language that the Web used, called hypertext markup
language (HTML), made it far easier to link information
from computers throughout the world. This development
effectively created an interactive index that enabled users to jump
easily from the resources of one computer to another,
effortlessly following an information trail around the world. The
of browsers in 1993 further simplified use of the Web and
the Internet, and brought about staggering growth in the Internet.
1990's, many businesses were created on the Internet. Some
were considered among the most valuable businesses in the
world. But their values often rested in their potential, or the
excitement people felt about this new way of doing business,
and few actually made a profit. By 2000, many of these companies
had gone out of business. Companies that operated
traditional retail businesses in addition to ones on the Internet were,
on the whole, more successful.
technologies continue to
increase the importance of the Internet. Handheld computers
and Internet-capable cellular telephones take advantage of satellite
communications to enable people to access the Internet from
any location. Wireless fidelity (also called wi-fi) and similar
systems use radio waves to link a computer wirelessly to the
Internet. Dedicated devices often called Internet appliances
or network computers provide e-mail and Web browsing ability
to people who do not require the greater capabilities of a PC.
Manufacturers increasingly add computer features to
television sets, and many of these sets provide Internet capabilities.
has moved rapidly from inception to global acceptance. Most computer
experts expect the Web to continue its rapid growth. New
technologies will aid its growth by adding such features as spoken-word
commands, instantaneous translation, and increased
availability of historical and archival material.