A computer is a device for working with
information. The information can be
Students use a computer in a
classroom.
People camping in the woods sometimes
carry pocket compasses so they do not get
lost.
BRITANNICA STUDENT ENCYCLOPEDIA Computer 171
The programs and data are kept permanently
on hardware called storage
devices. Most computers have a storage
device called a hard drive. The hard
drive stores data on a metal disk inside
the computer. Some storage devices put
data on disks that can be easily moved
from one computer to another. These
disks include CDs and DVDs. They
make it easy to share data.
Input and output devices are other types
of hardware. Input devices let the user
enter data or commands into the computer.
Input devices include the keyboard
and the mouse. Output devices let
the user see or hear the results produced
by the computer. Output devices
include the monitor (or screen), printer,
and speakers.
Communication, or network, devices
connect computers to each other. They
let people send data from one computer
to another and connect to the Internet.
Modems are communication devices
that can send data through telephone
wires or television cables. Some computers
use wireless communication devices.
They send data through the air using a
small antenna.
Computer software is divided into two
basic types—the operating system and
application software. The operating system
controls how the different parts of
hardware work together. Application
software gives the computer instructions
for doing specific tasks, such as word
processing or playing games.
How ComputersWork
Most computers are electronic devices.
This means that they work with electricity.
All computer data is carried in tiny
flows of electricity called electric currents.
The microprocessor contains
thousands or millions of tiny electronic
parts called transistors. The transistors
act as switches. They control how the
electric currents flow.
Computers use these electric currents to
represent the numbers 0 and 1. Computers
use only these two numbers
because transistors, like light switches,
have only two states—they are either on
or off. A transistor that is “on” represents
one of the numbers. A transistor that is
“off ” represents the other. Computers
use strings of 0s and 1s to stand for letters,
sounds, and all of the other data
they handle. For example, a computer
stores the word dog as three numbers:
01100100 (d), 01101111 (o), and
01100111 (g).
Computers can understand only these
patterns of 0s and 1s. All of the instructions
that a computer follows have to be
in this form. But people find it hard to
work with long number patterns. So the
people who write computer software,
called computer programmers, have
their own special languages. These
include programming languages called
BASIC, Java, and C++. The computer
turns programming languages into the
number patterns that it can understand.
History
An English inventor named Charles
Babbage designed the first computer in
An English
woman named
Ada Lovelace
studied Babbage’s
machine and
explained how
it could be
used to solve
problems. She
is called the
first computer
programmer.
BRITANNICA STUDENT ENCYCLOPEDIA Computer 173
the 1830s. It was mechanical, not electronic,
because scientists did not yet
know how electricity worked. The
design called for more than 50,000
moving parts. The machine was
designed to follow instructions that
people entered using punched cards. It
was so complex that Babbage never got
it built. But it is still considered to be
the first computer.
The first electronic computers were
invented in the 1940s. In place of
mechanical parts, they used electronic
switching devices called vacuum tubes.
These computers were so big that just
one of them filled a whole room. They
cost millions of dollars.
Computers improved after the
transistor was invented in 1947. The
transistor was an electronic switching
device that was much smaller and
worked better than a vacuum tube. By
1960 transistors had mostly replaced
vacuum tubes in computers. The new
computers were smaller and more
affordable than before.
The first computers with microprocessors
appeared in the early 1970s. A
microprocessor had many tiny transistors
on one small wafer, or chip. It made
personal computers possible. As more
transistors were included in microprocessors,
computers became faster and
less expensive.
#More to explore
Electricity • Electronic Games
• Electronics • Internet
Conakry
Population
(2004 estimate)
1,851,800
Conakry is the capital of theWest African
country of Guinea. It is the country’s
only large city. Part of Conakry is
on Tombo Island in the Atlantic Ocean.
The rest of the city is on the mainland
of Africa. A raised roadway connects the
city’s two parts.
Shipping brings money to Conakry.
The city is Guinea’s main port.
Government jobs and business services
The most powerful
computers
are called
supercomputers.
The fastest
supercomputers
of the 21st
century can do
trillions of calculations
per
second.
Computer chips are tiny but they can work
with a large amount of information very
quickly.
174 Conakry BRITANNICA STUDENT ENCYCLOPEDIA
