Computer technology, with its ability to transmit, store and retrieve
individual data and messages "has now emerged as one of the major
communication technologies in the world" (Chesebro & Bonsall, 1989, p.
30). However, a distinction must be made between the use of the computer as a technology or as a tool with which
to perform tasks such as wordprocessing or database retrieval, and its use as a medium of communication.
According to Neil Postman (1986), while "a technology. . .is merely a machine," it "becomes a medium as it employs a symbolic code, as it finds its place in a particular social setting" (p. 86). Thus, "a medium is the social and intellectual environment a machine creates" (p. 86). When people use their personal computers or workstations as a medium of communication, they use them to connect to a network of other users in order to exchange information and ideas within the medium's social and intellectual environment.
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Computer terms:
According to Neil Postman (1986), while "a technology. . .is merely a machine," it "becomes a medium as it employs a symbolic code, as it finds its place in a particular social setting" (p. 86). Thus, "a medium is the social and intellectual environment a machine creates" (p. 86). When people use their personal computers or workstations as a medium of communication, they use them to connect to a network of other users in order to exchange information and ideas within the medium's social and intellectual environment.
The Internet is one example of how the computer can be used as a medium
of communication. The Internet is
"a collection of networks around the world that links military,
university, and research sites. . . millions of computer [users] . . . participate
in a kind of electronic village" (Ward, 1992, p. 99).
The growth of the Internet has increased so rapidly that estimates of how many people are using the Internet for military, university, and research projects ranges from two million (Hafner & Markoff, 1991) to three million users daily (Schoffstall, 1991).
The growth of the Internet has increased so rapidly that estimates of how many people are using the Internet for military, university, and research projects ranges from two million (Hafner & Markoff, 1991) to three million users daily (Schoffstall, 1991).
Recognizing both the rapid growth of networking systems and the
increased volume of messages sent and received over the networks, computer manufacturers and software developers are continuing to enhance the networking
capabilities of their products. These enhancements
include enabling computer users who are connected to local and wide area
networks to have the ability to share and receive documents and messages (Apple
Computer, Inc., 1991; Norton & Schafer, 1992; Scherer, 1992).
There is no question that "the personal computer is gradually becoming the interpersonal computer" (Johansen, 1988, p. 1) and that with this shift, computerized communication is becoming "computer-user communication," transforming the manner and methods through which we communicate with one another. The relation of the personal computer "to the user will change from that of an isolated productivity tool to that of an active collaborator in the acquisition, use and creation of information, as well as a facilitator of human interaction" (Tesler, 1991, p. 86). Clearly, it is time to examine how the use of the computer as a medium of communication affects the process of human communication. This paper will specifically examine how the introduction and use of "groupware" not only extends our traditional definitions of human communication systems (interpersonal and small group), but it also challenges our definition of mediated communication. Further, this paper examines how groupware users create a new social and intellectual symbolic environment which the authors herein refer to as "interpersonal text."...
There is no question that "the personal computer is gradually becoming the interpersonal computer" (Johansen, 1988, p. 1) and that with this shift, computerized communication is becoming "computer-user communication," transforming the manner and methods through which we communicate with one another. The relation of the personal computer "to the user will change from that of an isolated productivity tool to that of an active collaborator in the acquisition, use and creation of information, as well as a facilitator of human interaction" (Tesler, 1991, p. 86). Clearly, it is time to examine how the use of the computer as a medium of communication affects the process of human communication. This paper will specifically examine how the introduction and use of "groupware" not only extends our traditional definitions of human communication systems (interpersonal and small group), but it also challenges our definition of mediated communication. Further, this paper examines how groupware users create a new social and intellectual symbolic environment which the authors herein refer to as "interpersonal text."...
Computer a Medium of Mass Communication
A computer remains your personal until and unless your work on it benefits you alone but when you put something on it in the form of a blog or a website which is accessible to anyone who wants then it becomes a Mass medium of Communication.….
Useful links
Computers in Communication
Computer-mediated Communication
A computer remains your personal until and unless your work on it benefits you alone but when you put something on it in the form of a blog or a website which is accessible to anyone who wants then it becomes a Mass medium of Communication.….
Useful links
Computers in Communication
Computer-mediated Communication
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DID YOU KNOW?
Lenovo Group Ltd. is a Chinese multinational technology company with headquarters in Beijing,
China, and Morrisville, North Carolina, United States.
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Founded: 1984, Beijing, China
Revenue: 44.91 billion USD (2016)
Samsung is a South Korean multinational conglomerate company headquartered in
Samsung Town, Seoul. It comprises numerous subsidiaries and affiliated
businesses, most of them united under the Samsung brand, and is the largest
South Korean chaebol.
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Acer Inc. is a Taiwanese multinational hardware and electronics corporation specialising in advanced electronics technology and is headquartered in Xizhi, New Taipei City, Taiwan.
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Acer Inc. is a Taiwanese multinational hardware and electronics corporation specialising in advanced electronics technology and is headquartered in Xizhi, New Taipei City, Taiwan.
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Apple Inc. is an
American multinational technology company headquartered in Cupertino,
California, that designs, develops, and sells consumer electronics, computer
software, and online services.
Apple MacBook MMGM2LL/A 12-Inch Laptop...
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Founded: April 1, 1976, Cupertino, California, United States
Products: iPhone, iPad, iPod, Macintosh, Apple Watch, QuickTime,Apple TV, iPad Mini, iWork, Final Cut Studio, Logic Studio
Binary code is used by computers to represent information. It
consists of the 0's and I s of the binary numeration system.
Bit, an abbreviation of the term 6/nary digit may be either
the digit 0 or 1.
Byte is a group of bits that act as a single unit of
information, such as a letter or numeral.
Database is an organized collection of information stored on a
magnetic disk or other direct-access storage device.
File storage device is any device used to save information until it is
needed again.
Hardware refers to the physical parts of a computer system. Input is
any information that a user enters into a computer. Mainframe is a large, powerful computer that many people can use
at once. It can store large amounts of information.
Memory is the part of a computer that stores information. Microprocessor is a miniature electronic device consisting of
thousands of transistors and related circuitry on a silicon chip. The device
holds the processor and some memory.
Modem is a device that allows computer users to communicate
with one another over telephone lines.
Network is a system consisting of two or more computers connected
by high-speed communication lines.
Operating system is a type of software that controls the operation of
a computer system.
Output is any result provided by a computer.
Peripheral equipment consists of input devices, output devices, and file
storage devices.
Personal computer is a desktop or handheld computer designed for
general-purpose use.
Program is a set of instructions to be carried out by a computer,
written in a computer language.
Simulation is the representation or imitation of a situation or
system on a computer, usually with a mathematical model. The purpose is to
predict and analyse what is likely to occur under various conditions.
Software refers to the programs used by a computer to perform
desired tasks.
How a computer works. Computer systems come in a wide range of sizes and
contain varying types of equipment. Nevertheless, ail digital computers work
essentially the same way. The diagram above illustrates the flow of information
through a personal computer system. A human operator uses input equipment to provide
data and instructions to the computer. The processor then
performs calculations on the data, while the memory stores information during processing. The
results then are sent to the output equipment, which presents them to the user. File storage devices enable
information to be saved for future use.
Computers come in a wide range of sizes. A mainframe computer system may fill a large room. A
personal computer fits on a desk top. Computers are controlled by a microprocessor, a
chip that fits through the eye of a needle.
Computers enable engineers to predict how a machine will work. The photograph on
the left shows a computer image of a car being tested for wind resistance.
A computer simulation can accurately represent an operation, situation, or
system. The first three photographs above show computer-generated images of a
bomb's nose cone striking a steel plate. The fourth photograph—which shows an
actual nose cone after a test—reveals the great accuracy of the computer
simulation.
Computer-aided design programs are important in many fields. An engineer uses a light
pen to modify the design of an aeroplane. A fashion designer can consider her
design in various colours and patterns on a computer screen.
Computers use X-ray data to generate three-dimensional images of body parts
such as the human spine. The images help doctors identify disorders without
performing surgery.
Schools use computers as
a teaching aid. An elementary school teacher and his students work at a
computer.
Computers help meteorologists forecast the weather by solving equations that
describe the behaviour of the atmosphere.
Computer games entertain children and adults. Many games display detailed moving pictures on monitors or TV screens.
An integrated circuit contains all of the tiny devices that make up the
processor on a single, tiny chip. This photograph, taken through a microscope,
shows a portion of such a chip.
Programming languages enable people to write instructions that a computer
can translate and execute. The languages allow the programmer to concentrate on
the basic ideas of an operation, instead of on the details of what the machine
must do. The BASIC and APL programs shown above both contain instructions for
finding the average of a list of numbers. The steps in machine language show
how a computer interprets and executes this type of program in any language.
Computer firms manufacture hardware, software, and supplies. In this picture, quality
control workers check computers on an assembly line.
A repair specialist services a personal computer. Many computer makers and
dealers provide repair services.
Computer programmers write instructions for computers to follow. This
programmer is entering a program into a computer.
The punched-card tabulating machine
invented by Herman Hollerith was the first successful computer. It was used to
compute the results of the 1890 United States census.
ENIAC, completed in 1946, was the first general-purpose
electronic digital computer. The enormous machine was invented by J. Presper
Eckert, Jr., and John W. Mauchly.
IBM's personal computer introduced in 1981, enjoyed great success. The small
size and low cost of the computers made them popular among individuals,
schools, and businesses.
A supercomputer can solve large, complicated numerical problems with
amazing speed. The Cray supercomputer shown above generated a detailed image
of part of the main engine of a space shuttle.
Computer is a machine that performs calculations and processes
information with astonishing speed and precision. A computer can handle vast
amounts of information and solve complicated problems. It can take thousands
of individual pieces of data and turn them into more usable information—with
blinding speed and almost unfailing accuracy. The most powerful computers can
perform billions of calculations per second.
Computers have changed the way people
work. They handle many tasks in business, education, manufacturing,
transportation, and other fields. Many tedious tasks performed by large numbers
of clerical workers are now done by computers. They provide scientists and
other researchers with a clearer understanding of nature. They give people who
work with words an effective way to create documents. They enable designers
and artists to see things that have never been seen before. Computers produce
new information so quickly and accurately that they are changing people's views
of the world. People can access large electronic databases remotely. For these
and other reasons, the computer is one of the most interesting and important
machines ever invented.
The most common type of computer, by far,
is the digital computer. Digital means having to do with numbers.
Digital computers perform tasks by changing one set of numbers into another
set. All data — numerals, pictures, sounds, symbols, and words — are
translated into numbers inside the computer. Everything a digital computer can
do is based on its ability to perform simple procedures on numbers—such as
adding, subtracting, or comparing two numbers to see which is larger. Digital
computers are so widespread that the word computer
alone almost always refers to a digital computer. The largest digital computers
are parts of computer systems that fill a large room. The smallest digital
computers — some so tiny they can pass through the eye of a needle — are found
inside wristwatches, pocket calculators, and other devices.
All digital computers have two basic parts
— a memory and a processor.
The memory receives data and holds them until needed. The memory is made up of
a huge collection of switches. The processor changes data into useful
information by converting numbers into other numbers. It reads numbers from the
memory, performs basic arithmetic calculations such as addition or subtraction,
and puts the answer back into the memory. The processor performs this activity
over and over until the desired result is achieved. Both the memory and the
processor are electronic — that is, they work by sending electrical signals
through wires.
The smallest digital computers consist
only of the memory and the processor. But larger digital computers are part of
systems that also contain input equipment and
output equipment. The operator uses an input device, such as a
keyboard, to enter instructions and data into the computer. After processing is
complete, an output device translates the processed data into a form
understandable to the user—words or pictures, for example. Typical output
devices include printers and visual displays that resemble television screens.
People can think about problems and figure
out how to solve them. But computers cannot think. A person must tell the
computer in very simple terms exactly what to do with the data it receives. A
list of instructions for a computer to follow is called a program.
People have used calculating devices since
ancient times. The first electronic digital computer, built in 1946, filled a
huge room. Since then, rapid improvements in computer technology have led to
the development of smaller, more powerful, and less expensive computers.
In addition to digital computers, there
are two other general types of computers: analog computers and hybrid computers.
Analog computers work directly with a physical quantity, such as weight or
speed, rather than with digits that represent the quantity. Such computers
solve problems by measuring a quantity, such as temperature, in terms of another
quantity, such as the length of a thin line of liquid in a thermometer. Hybrid computers combine the features of analog and digital computers.
They have many of the same kinds of parts as an analog computer. But like
digital computers, they process data by manipulating numbers. This article focuses
on digital computers. For information on analog computers, see Analog computer.
The importance of the computer
Computers are tremendously important in a
variety of ways. For example, they simplify many difficult or time- consuming
tasks to an extraordinary degree. They provide businesses, governments,
individuals, and institutions with an efficient way to manage large amounts of
information. Computers also help people to understand things better by allowing
them to make models and test theories.
The value of computers lies in their
ability to perform certain basic tasks extremely quickly and accurately. These
tasks include (1) solving numerical problems, (2) storing and retrieving
information, and (3) creating and displaying documents and pictures.
Solving numerical problems. One of the most important and most difficult jobs
performed by computers is the solution of complicated problems involving numbers.
Computers can solve such problems amazingly quickly. In many cases, the
solutions show how certain things work, behave, or happen.
In engineering and the sciences,
the knowledge of how something works is often expressed in the form of an equation.
An equation is a two-part mathematical sentence in which the parts are equal to
each other. Engineers and scientists use equations or groups of equations to
show how various things relate to one another. They use the solutions to these
equations to predict what will happen if certain elements of a situation or an
experiment are changed. Engineers and scientists rely on computers to solve the
complicated sets of equations that they use to make predictions.
For example, with the help of a computer,
an engineer can predict how well an aeroplane will fly. A large, complex set
of equations expresses the relationships between the various parts of an
aeroplane and what happens when the aeroplane flies. The engineer enters the
numbers for the size and weight of a certain aeroplane's parts. The computer
then solves the equations for this particular aeroplane. Based on the
solutions, the engineer can predict how well the plane will fly. The engineer
then might decide to change the size or weight of one of the aeroplane's parts
to change the way it flies. Thus, the computer helps the engineer simulate
(imitate) various conditions.
Computers help people develop and test
scientific theories. A theory is a proposed explanation for how or why
something happens. Theories, like known relationships, are often expressed as
equations. Some equations are so complicated or time-consuming to solve that it
would be impossible to develop the theory without the help of computers.
Computers are particularly useful in developing and evaluating theories about
things that are difficult to observe and measure.
For example, an astronomer can use the
problem solving ability of computers to develop theories about how galaxies
are formed. First, the astronomer proposes a set of equations about a group of
stars. A computer performs the calculations needed to solve the equations. The
astronomer can then use the solutions to predict the shape of the galaxy that
the stars should form if the theory is correct. To test the theory, the
astronomer can observe a real galaxy to see if it has the predicted shape. If
the galaxy's shape agrees with the theory, the astronomer becomes more
convinced that the theory is correct. If the galaxy's shape does not agree with
the theory, the theory is wrong. The equations must be changed, and new
calculations must be performed.
In economics and finance, computers solve equations to make predictions about
money. Many of the equations that economists and business people use to make
long-range predictions are extremely complicated.
But some of the most widely used of all
computer programs rely on fairly simple equations. Such programs help people
and businesses work out their taxes, create budgets, and calculate the value of
their investments.
Storing and retrieving information. People
use computers to store unbelievably large quantities of information.
Information stored in a computer is sometimes called a database.
Databases can be enormous— for example, a country's entire census might be contained
in a single database. A computer can search a huge database quickly to find a
specific piece of information. In addition, the information can be changed easily
and quickly—often in less than a second.
The efficiency with which computers store
and retrieve information makes them valuable in a wide range of professions.
For example, scientists use computers to store and quickly find results of
experiments. Libraries use computer catalogues to hold information about their
collections. Hospitals use computers to maintain records about their patients.
Governments store election returns and census information on computers.
All kinds of businesses rely on computers
to store large quantities of information about their employees, customers, and
products. Computers also allow markets for stocks, bonds, currency, and other
investments to keep track of current prices around the world. Banks maintain
many kinds of records on computers, such as account balances and credit card
information. Anyone who uses an automatic teller machine
(ATM) is using a computer terminal.
When an identification card and number are entered, the ATM can provide account
information, dispense cash, and transfer funds between accounts.
Creating and displaying documents and
pictures. Computers can store a
huge number of words in a way makes it easy to manipulate them. For this
reason,
word processing is one of the most important and widespread uses of
computers. A word-processing
program allows people to type words into a
computer to write articles, books, letters, reports, and other kinds of documents.
Word-processing programs make it easy for
people to change text that has been typed into a computer. For example, they
can quickly correct typing or spelling errors. Words, sentences, and entire
sections of a document can be added, removed, or rearranged. If a computer is
connected to a printer, the document may be printed onto paper at any time.
Business people, journalists, lawyers, scientists, secretaries, and students
are among those who benefit from word-processing programs.
Computers are also important in the
publishing industry. For example, most books, magazines, and newspapers are
typeset by computers. In addition, a process known as desktop publishing enables people to design and produce newsletters and
other documents on personal computers. Documents that have been created in
this manner look almost as if they have been professionally typeset.
Computer graphics—the use of computers to
make pictures—make up one of the most fascinating and fastest-growing areas of
computer use. Computers can produce pictures that look almost like photographs.
First, the computer solves equations that
predict how an object should look. It then uses these predictions to display a
picture on a computer terminal screen or to print a picture on paper.
Computer programs that perform computer-aided design (CAD) are important in many fields, particularly
engineering and architecture. CAD programs create pictures or diagrams of a
new object. They then solve equations to predict how the object will work. Engineers
and architects use CAD programs to design aeroplanes, bridges, buildings,
cars, electronic machinery, and many other machines and structures.
Computers also can produce pictures by
converting information into pictorial form. The pictures can serve a variety of
purposes. For example, computers enable business people, economists, and
scientists to plot graphs from lists of numbers.
In a technique called computerized tomography, or the CT scan, a computer uses
X-ray data to construct an image of a body part on a screen. Doctors use these
images to diagnose diseases and disorders (see Computerized tomography). Sophisticated radar systems use computers to produce
detailed pictures, often for military use.
Computer graphics also are used to create
electronic video games. Terminal monitors or TV screens can display game
boards and moving pictures. The player may use a keyboard or some other device,
such as a mouse or
a joystick, to play computer games.
Computer designers are experimenting with
using computer graphics to create virtual reality — an
artificial world in which the computer user can seemingly move about and handle
objects. One virtual reality system has a headset with two tiny display
screens, one screen for each eye. Images on the screens produce a three- dimensional
view. Sensing devices contained in a special glove tell the computer when the
user moves the fingers or hand. The computer then changes the images to create
the illusion of, for example, opening a door.
The images do not have nearly the detail of
what is seen in the actual world. In addition, there is a delay between hand
movements and the corresponding changes in the images. However, virtual reality
has a variety of applications. These applications range from simple game sets
to sophisticated equipment used to control robots.
Other uses. Many complex machines need frequent adjustments to
work efficiently. Small computers can be installed inside these machines and
programmed to make these adjustments. In modern cars, such embedded
(enclosed) computers control certain aspects of operation, such as the mixture
of fuel and air entering the engine. Today's commercial airliners and military
planes carry computers that help control the aircraft. Embedded computers also
control the movements of industrial robots and are used to guide modern weapons
systems such as missiles and field artillery, to their targets.
Computers can help solve many complicated
problems that do not involve numerical equations. Doctors, for example,
investigate illnesses, decide on diagnoses, and prescribe treatments. They
solve such problems by applying their knowledge and experience, not by solving
equations. A branch of computer science called artificial intelligence uses programs that help solve problems by applying
human knowledge and experience. Artificial intelligence systems called expert systems enable computers programmed with vast amounts of
data to "think" about numerous possibilities—such as diseases that
certain symptoms could indicate—and make a decision or diagnosis.
Computers also can be used to communicate
information over long distances. They can send information to each other over
telephone lines. As a result, computers keep banks, newspapers, and other
institutions supplied with up-to-the-minute information. A computer network consists of many computers in separate rooms,
buildings, cities, or countries, all connected together. Computer networks
allow people to communicate by using electronic mail—a document typed into one computer and
"delivered" to another. Such documents generally travel in only a
few minutes, even if they are being sent over a long distance.
Computers also are used in teaching.
Programs that perform computer-aided instruction
(CA1) are designed to help students at all levels, from elementary school to
the university level. The student sits at a computer terminal. The terminal's
screen displays a question for the student to answer. If the answer is wrong
or incomplete, the computer may ask the student to try again. It then may supply
the correct answer and an explanation. CAI is also used in some adult education
programs and as part of the employee-training programs of some corporations.
Basic principles of computers
A computer receives individual pieces of
data, changes the data into more useful information, and then tells the
operator what the information is. For example, a person who wants to find the
sum of four numbers enters them into the computer. In only a fraction of a second,
signals that represent these numbers are changed into
signals that represent the sum. The computer then displays the sum for the
user.
How a computer operates. People use input devices to enter data into
computers. One of the most common input devices is the computer terminal, which looks like a typewriter keyboard combined with
a television screen. Data that are typed on the keyboard appear on the screen.
At the same time, the data go to the memory. The memory also stores a
program—the step-by- step series of instructions for the computer to follow.
The processor manipulates the data according to the program.
The processed information is sent to an
output device, which presents it to the computer user. In many cases, the
computer terminal that served as the input device also acts as the output device,
and its screen displays the results. Printers are another important kind of
output device. File storage
devices are used to save information and
programs for future use.
All data handled by computers, including
words, enter the processor in the form of digits. Computers commonly use the
digits of the binary numeration
system (see Numeration systems (the binary system). Unlike the familiar decimal
system, which uses 10 digits, the binary system uses only two digits: 0 and 1.
These digits are called bits. Different
combinations of bits rep- t- resent letters, symbols, and decimal numerals.
Each such combination of bits is called a byte.
For example, according to one standard code, the binary representation for the
letter A is 100 0001, while the binary representation for the letter Z is 101
1010. Each symbol and decimal numeral also is represented by a specific combination
of 0's and l's.
Each of a computer's thousands of tiny
electronic circuits operates much like an ordinary light switch. When a circuit
is off, it corresponds to the binary digit 0. When a circuit is on, it
corresponds to the digit 1. Binary digits, like decimal numbers, can be added,
subtracted, multiplied, and divided. Thus, a computer can perform all the
basic arithmetic operations.
Computer hardware and software. The physical equipment that makes up a computer
system is called hardware. Hardware includes input and output devices, file
storage devices, the memory, and the processor.
The input and output devices and the file
storage devices are also known as peripheral equipment.
Computer software
consists of the programs that a computer uses to perform a task. People can
either create or purchase software. Computers have vast and varied capabilities
because of the many different kinds of available software.
Kinds of computers
Computers vary widely in size, speed, and
ability. The size of a computer partly determines the kinds and number of jobs
it can do. But even a small computer can perform complicated tasks. For
example, a modern desktop computer has more computing power than the huge,
room-filling computers of the early 1960's.
The microprocessor— an electronic device consisting °f thousands of
transistors and related circuitry on a silicon chip—plays an important role in
almost all modern computers. A single microprocessor has the computing power of
a larger computer but generally costs far less. The small size and relatively
low cost of microprocessors have made them valuable as components in computer
systems.
Digital computers may be grouped into
three categories: (1) embedded computers, (2) personal computers and
workstations, and (3) mainframes. The borders between these categories change
constantly as smaller, more powerful computers are developed.
Embedded computers control the operation of various types of machinery.
Virtually all embedded computers are microprocessors. Such machines as cars,
digital wristwatches, telephones, and videotape recorders contain embedded
computers.
Personal computers and workstations are
computers used by one person at a time. Such a computer usually fits on a desk
top, and some personal computers can be held on the lap or in the hands. People
commonly use personal computers for such activities as word processing,
storing and updating information, performing simple calculations, and playing
computer games. These computers also are valuable to business people, who use
them to manage information about their inventories, sales figures, customers,
and employees.
Personal computers contain one or more
microprocessors. By modern standards of computer speed and capacity, personal computers
execute programs slowly and have limited memory and file storage capacity. Workstations are more powerful than personal computers,
and better suited to solving difficult engineering, graphics, or scientific
problems. Workstations are generally connected to form computer networks.
These networks allow operators to exchange information very rapidly. They also
enable printers and file storage devices to be shared by many workstations.
One important type of computer network, the local area network (LAN), connects workstations located within the same
building or in neighbouring buildings. A wide area network (WAN) links workstations over large areas.
Mainframes are fast computers with large
memories and file storage systems. These powerful computers solve very
complicated problems and manage huge quantities of information. Most mainframes
are housed in several large cabinets. Some mainframes do a single job, such as
copying and storing the information generated by a laboratory experiment.
Others perform many different tasks. Minicomputers and superminis
have many of the capabilities of mainframes, but they are smaller and less
expensive.
On a large mainframe, hundreds of people
may be logged on (running programs) at one time. The use of a single
powerful computer by many users at once is called time sharing. The mainframe appears to run many programs at the
same time. However, the computer actually switches rapidly from program to
program, doing a bit of work on one and then hurrying on to work on another.
The fastest mainframes are called supercomputers. Supercomputers solve numerical problems as quickly as
possible based on existing technology. They are used to model weather systems,
to design cars and aircraft, and in many other ways. But supercomputers are
rare, because they are extremely expensive. Individual supercomputer
users—mostly scientists and engineers at large scientific
installations—sometimes run programs by means of long-distance computer
networks.
In recent years, mainframes known as parallel computers have provided great increases in speed over other
computers. Most computers have a single processor. But a parallel computer has
many processors that all operate at once. Each processor can work on a separate
piece of a program. As a result, the program can be run much more quickly than
on a computer with only one processor. The fastest supercomputers in the world
are parallel computers. But parallel computers may even serve as especially
fast workstations.
How a computer works
Computers can perform many different
activities because they can store huge lists of numbers and do arithmetic
very rapidly. All computers work essentially the same way. A computer encodes
(translates) numbers, words, pictures, sounds, and other forms of data into the
0's and Vs of the binary numeration system. The computer's processor
manipulates the binary numbers according to specified instructions. All changes
of the data are accomplished by performing arithmetical calculations on these
binary numbers. Thus, the binary numbers that represent the data are changed
into binary numbers that represent the desired information. The results are decoded
'translated back] from binary numbe into decimal numbers, words, pictures, or
some other form.
The operation of a computer can be broken
down into three steps. They are (11 entering and encoding data and
instructions, (2) processing data, and (3) decoding the results and producing
output. The storing of information occurs during all three steps of the
computing process.
Entering and encoding data and
instructions is performed using
input equipment. This section explains how the computer encodes data entered
through a terminal. It also describes a number of other input devices
Terminals enable computer users to type characters (letters and numerals) directly into the computer. A
terminal includes a keyboard unit and a monitor.
The monitor usually consists of a cathode-ray tube
(CRT). A CRT is a vacuum tube with a screen like that of a television (see
Vacuum tube). The CRT display makes it possible for the user to check the data
being entered into the computer and to make corrections if necessary.
As each character is typed, the circuitry
inside the terminal puts the character's binary code into a temporary storage
location called a buffer. As soon as a code
appears in the buffer, the processor executes an instruction that moves it
from the buffer to the computer's memory. The monitor also has a buffer.
Whenever the processor sends a code into this buffer, the corresponding
character appears on the screen.
Other input devices are also used with
monitors. For example, some terminals enable users to communicate with the
computer by drawing pictures or diagrams directly on the screen with a light
pen. Such units encode drawings directly from the monitor. A device called a mouse
can be used to give commands to a computer. When this handheld box is moved on
a flat surface, it causes a pointer to point at a specific instruction or piece
of data displayed on a monitor. Clicking a button on the mouse causes the
instruction to be carried out or the data to be moved or changed.
Modems are devices that allow computers to communicate with
other computers by using telephone lines. A modem translates binary codes into
tones. At the other end of the line, another modem translates these tones back
into digital data.
Disk drives and tape drives perform many functions in the operation of the computer.
One of these functions is providing input in binary form. A disk drive is a machine
that, among other things, reads 0's and 1's that are magnetically encoded onto
disks. This information then goes to the buffer and the memory. A disk system
provides quick and direct access to specific information located anywhere on
a disk. Flexible magnetic disks called floppy disks or diskettes are widely used to
provide input to personal computers. Hard disks are used with larger computer systems, as well as with
some personal computers.
Tape drives and magnetic tapes work in
much the same way. However, a tape must be unwound or rewound to the location
that contains the desired information. As a result, it takes longer to read
information from a tape than from a disk.
Optical scanners also read data and instructions. Some scanners
optically sense bar codes and other marks printed on identification and library
cards, grocery items, or documents. They then change these codes into
electrical signals. Other scanners read information from compact discs or optical disks.
Such disks contain digitally encoded information that can be read by a laser
beam.
Other input devices include a joystick
for moving figures about on a screen and a graphic tablet consisting of a pad and a special pen for producing
illustrations. Such devices are used with some personal computers. Voice activators enable computers to understand spoken words. Some
mainframes obtain input by means of card readers, which take information from punched cards. The
pattern of punches represents letters, numbers, and other symbols. Card
readers once were popular, but today they are used less frequently.
Processing data. The processor, also called the central processing unit or CPU, is the heart of the
computer. It manipulates the binary numbers that represent input according to a
program, and converts them into binary numbers that represent the desired
result.
Since the development of the integrated circuit in the WCTs, the processor in many computers is contained
°n a single microprocessor—a silicon chip no larger than a fingernail (see
Integrated circuit). All the devices and wires that make up the processor are
packed onto the surface of the chip. Silicon is one of a group of materials
called semiconductors (see Semiconductor). The circuitry on the chip
contains many tiny devices called transistors.
A transistor can either stop electric current or allow it to flow (see
Transistor). The processor of a computer consists of two parts: (1) the control unit and (2) the digital logic unit.
The control unit directs and coordinates the operations of the entire
computer according to instructions stored in the memory. The control unit must
select the instructions in proper order because their sequence determines each
step in the operations. Each set of instructions is expressed through a binary
operation code that specifies exactly what must be done to complete
a job. The operation code also provides information that tells where data for
the processing operation are stored in the memory. The control unit interprets
the instructions and relays commands to the logic unit. It also regulates the
flow of data between the memory and the logic unit and routes processed
information to output or file storage devices.
The digital logic unit sometimes known as the arithmetic/logic unit or ALU, manipulates data received from the memory. It carries
out all the functions and logic processes required to solve a problem.
Computers use logic to perform arithmetical calculations—addition, subtraction,
multiplication, and division.
In the digital logic unit, electronic
circuits called registers temporarily store data from the memory. The data
consist of electrical signals that represent binary digits. An electrical
signal that has a low voltage level represents 0, and a signal that has a high
voltage level represents 1.
To carry out an arithmetical calculation,
the electrical signal for each input travels on a wire to another circuit. The
answer comes out on a wire from the other end of the circuit. There are a
number of basic circuits. Three such circuits are the AND-gate,
the OR-gate, and the NOT-gate or inverter.
The basic circuits are combined in different ways to perform arithmetic and
logic operations with electrical signals that represent binary digits. For
example, one combination of logic circuits performs addition. Another
combination compares two numbers and then acts on the result of the comparison.
After an operation has been completed, the
result may be sent to the memory for storage until it is needed for another
operation. In many cases, the result is sent to an output device or a file
storage device.
Decoding the results and producing output.
People use output equipment
to get information from computers. Output
equipment translates the electrical signals that represent binary numbers into
a form that the user can understand. Often, it also serves as input equipment.
There are many types of output devices, such as terminals, printers, modems,
and disk and tape drives.
Terminals, in addition to serving as input equipment, display
output on the monitor. As information travels from the processor to the
terminal, it moves through the buffer that was used in the input function. On a
terminal,
a user can receive data in the form of
words, numbers graphs, or pictures.
Printers produce output on paper. Like terminals printers have
buffers. To print a character, the processor puts the binary code for that
character into the printers buffer. The printer prints the character that
corresponds to the code. Some printers operate much like typewriters. Others
use heat, special chemicals, lasers, or combinations of these methods to place
characters on paper
Modems, which translate sounds into binary numbers during
the input function, can also provide output by translating binary numbers into
sounds. As a result they enable users to receive information from distant
computers.
Disk drives and tape drives also serve as both input and output equipment.
Magnetic disks and tapes receive output in binary form. The drives interpret
binary information from disks and tapes and present it to the user, often on a
monitor. Output data presented on disks and tapes can easily be put back in the
computer when needed.
Other output devices include plotters, key punch machines, and audio devices.
Plotters use pens to create drawings, diagrams, and graphs on paper or clear
plastic. Key punch machines record data by punching holes in cards or paper
tape. Audio devices produce spoken words through a type of telephone or
loudspeaker. Such devices are becoming increasingly important.
Storing information. Computers can store
information in two types of locations during the computing process—the memory
and file storage devices. Memory, which is built into the computer, holds
instructions and data during processing. File storage devices provide long-term
storage of large amounts of information.
Memory, also called the internal memory or main memory,
stores information and programs inside the computer. The memory receives data
and instructions from an input device or a file storage device. It also receives
information from the processor. The memory stores only the information that is
currently needed by the processor. After the processor has finished with it,
the information is transferred to file storage devices for permanent storage or
sent directly to an output device for immediate use.
The devices and wires that make up the
memory can be built from integrated circuits that fit onto one or more chips.
The circuits, wires, and transistors form many memory cells capable of storing binary digits. These cells are
arranged into groups. Each group is assigned an address—
a number that makes it possible to locate specific pieces of information
quickly.
File storage devices, also called auxiliary storage units, can store huge amounts of information for long
periods of time. Such units are slower than the memory that is built into the
computer. But they can hold much more information, and they are less expensive.
For this reason, file storage devices are commonly used to store large
quantities of data, programs, and processed information.
The most important file storage devices
are magnetic disks and magnetic tapes. Disks and tapes are operated by disk
drives and tape drives, which also serve as input and output equipment. These
units encode data onto signals that represent the 0's and I s of binary code
into magnetism. Every 0 is represented on the disk or tape by a little magnet
pointing in a certain direction, and every 1 by a magnet pointing in the
opposite direction. To read information from a disk or tape, the drive unit
translates the magnetic signals into electrical signals and sends them to the
memory. Magnetic disks are said to be random-access devices because any part of the information on them
can be inspected or replaced with ease.
Some other types of file storage devices
contain readonly memory (ROM)— information that the computer cannot change.
ROM units may consist of a compact disc, a cartridge, or a silicon chip. They
are used to store large databases and programs for computer games.
Programming a computer
Programming involves the preparation and
writing of detailed instructions for a computer. These instructions tell the
computer exactly what data to use and what sequence of operations to perform
with the data. Without programs, a computer could not solve problems or deliver
any other desired result.
Some people prepare their own computer
programs. But in many cases, computer scientists and other computer
specialists called programmers
write instructions for computers. They use programming languages that consist of letters, words, and symbols, as well
as rules for combining those elements.
A computer cannot work directly with a
program written in a programming language. The instructions must be translated
into a machine language composed of binary digits. These digits represent
operation codes, memory addresses, and various symbols, such as plus and minus
signs. Machine language is also known as low-level language.
Special programs called compilers
and assemblers translate programming languages into machine language.
Another special type of program called an operating system contains instructions for the operation of a
computer. It controls the input and output devices, and it reads and responds
to user commands. It also places programs and data into the memory and makes
sure that the processor executes the right programs. Thus, the operating system
combines the many separate parts of a computer into a single useful system.
Compilers, assemblers, and operating
systems may be viewed as "smart (intelligent) programs" because they
enable a computer to understand complicated instructions. The user
communicates with the smart program, and the smart program communicates with
the computer. A computer combined with a smart program acts like a different,
smarter computer. This combination is called a virtual machine.
Preparing a program begins with a complete
description of the job that the computer is to perform. This job description
is obtained from the person for whom the program is being prepared, such as a
business manager or an engineer. It explains what input data are needed, what
computing must be done, and what the output should be. Computer programmers use
the description to prepare diagrams and other pictorial aids that represent
the steps needed to complete the task. The programmers may produce a diagram
called a systems flow chart that shows how all the major parts of the job fit
together systematically.
After a computer program is written, it is
tested on the computer for mistakes. Computer experts refer to mistakes in programs as "bugs"
and the testing of programs as "debugging."
A program generally is entered into a
computer in what is known as an interactive environment.
In such an environment, the programmer enters part of the program on a
computer terminal. The computer's operating system responds immediately,
telling the programmer how the computer will interpret each instruction. The programmer
then can analyse each response. Programs that result from this interaction
between the programmer and the computer generally are stored on some type of
file storage device until needed.
Using programming languages. Computers appear to work directly with programming
languages. But the smart program, not the computer, actually understands these
languages. The smart program translates a program into machine language. It
then enters the translated version into the computer's memory. The processor
reads and executes each translated instruction.
There are many different high-level programming languages. Some of them closely resemble
the language of mathematics. Others enable programmers to use symbols and
various everyday expressions, such as "READ," "PRINT," and
"STOP." All high-level languages are designed to let the programmer
concentrate on the basic ideas of a task rather than on the details.
The language that a programmer uses
depends largely on the job to be done. If a task involves processing business
data, the programmer would most likely use COBOL (COmmon business Oriented
language). However, programming a computer to solve complicated scientific
problems might require the use of a mathematically oriented language, such as
FORTRAN (Formula 772/Wslation).
Some high-level languages can be used for
business, technical, or scientific programming. Such languages include APL (A
Programming language); C; and LISP iLISt Processor).
Another commonly used programming language
is BASIC (beginner's 411-purpose symbolic Instruction Code). BASIC is well suited for writing relatively simple programs
for personal computers. Many primary schools and secondary schools that offer a
course in programming teach BASIC because it is easy to learn and to use. Pascal,
named after the French mathematician and scientist Blaise Pascal, also is
taught in a large number of schools.
Some computer programs may be written in
an assembly language. This kind of language is harder to use than a
high-level language. The programmer must state each instruction very precisely,
with much more detail than is needed when using a high-level language.
The computer industry
The manufacture, development, sales, and
servicing of computer hardware and software make up one of the largest and most
important industries in the world. Governments, institutions, and virtually
all industries rely upon computers. By the year 2000, the computer industry is
expected to be the second largest industry in the world in terms of annual
revenue. Only agriculture will be larger.
The first commercial digital computers
were manufactured in the 1950's. Throughout the 1950's, as the importance of
computers increased, people's acceptance of them increased as well. More than
10,000 computers were in operation by 1961. Ten years later, the number of
computers exceeded 100,000. By 1990, there were about 100 million
data-processing computers—that is, computers that require input and output
equipment-in operation worldwide.
The United States has the largest computer
industry in the world, employing more than 1 million people, it also has more
computers than any other country—more than 50 million, or about half the
world's computers. Japan ranks second with more than 9 million computers, about
11 per cent of the world total. European countries account for nearly 25 per
cent of all computers.
The economic growth of the computer
industry has matched the increase in the number of computers. The United States
produced about $1 billion worth of computers in 1958. Ten years later, the
figure had reached 54.8 billion. By 1978, United States manufacturers produced
more than $16.6 billion worth of computer equipment each year.
In the late 1970's, the computer
industry's rate of growth increased dramatically. Advances in both computer
technology and manufacturing technology enabled the United States to sell
computers worth more than $30 billion in 1981. By 1990, the U.S. computer industry's
annual revenues had topped $100 billion, and they continued to grow.
Manufacturing. From a few dozen companies in the early 1960's, the
computer industry has grown to more than 10,000 firms around the world. These
companies manufacture computers and such peripheral equipment as modems and
printers. They also develop and publish software and provide various computer
supplies, such as magnetic disks.
Some companies produce entire computer
systems, ranging from personal computers to supercomputers. A large number of
companies manufacture computer components, including processors. Some companies
produce input and output equipment, such as terminals and printers. Other
important products of the computer industry include equipment that increases a
computer's abilities to provide visual and audio output, and the network
boards and cables used to create computer networks.
The largest computer manufacturer in the
United States—and the world—is International Business Machines Corporation
(IBM). By the late 1980's, IBM's annual sales had topped $50 billion. Digital
Equipment Corporation (DEC) ranks second in the United States, with more than
$9 billion in sales in 1988. Unisys is the third largest U.S. manufacturer,
with more than $7 billion in annual sales in the late 1980's. Other leading
U.S. computer companies include Apple, Compaq, Cray, Tandy, and Zenith.
The largest computer manufacturer outside
the United States is Japan's Fujitsu, followed closely by NEC Corporation, also
of Japan. Each company had sales of more than $9 billion in 1988. The leading
computer companies in Europe include Croupe Bull of France, Italy's Olivetti,
and Siemens AG of Germany.
Research and development. The constant
increase in computer power is a major reason for the computer industry's
success. Such increases in power result from computer science research and development,
which take place at businesses and universities throughout the world.
One area of great interest to computer
researchers and manufacturers is memory speed and capacity. As software becomes
more complex, it requires more computer memory in order to operate properly.
At the same time, sophisticated software can manipulate increasingly large
amounts of data, which occupy more space in the computer's memory.
The storage of information files is
another important area of study.- Researchers work to develop increasingly
compact ways to store data, such as on magnetic disks, compact discs, or other
devices.
Artificial intelligence is an exciting
area of software research. Experts in this field design computer systems to
perform tasks that appear to require intelligence, such as reasoning and
learning. In this manner, artificial intelligence experts hope to increase the
ability of computers to respond to problems in a "human" manner.
See Artificial intelligence.
Sales.
Computers are sold in a variety of ways. Large manufacturers of computers have
teams of sales professionals. These teams call on corporations and institutions,
analyse their needs, and provide the appropriate combination of hardware and
software. Some companies purchase computer systems and components from a
variety of sources. They assemble the components and then sell the finished
products to computer users.
Retail outlets play an increasingly
important role in the sale of personal computers. Chains of computer stores
sell many personal computers. Some general merchandise stores also sell
computers, programs, and various accessories.
Service and repair. Because people depend on their computers, it is
important to have the machines serviced periodically and repaired promptly when
necessary. Many computer manufacturers offer service contracts that provide
for regular maintenance and prompt repairs. When a large computer system breaks
down, service technicians must visit the computer itself. Some large businesses
and institutions have their own computer maintenance staffs.
Many retail outlets that sell personal
computers also offer repair service to their customers. These retailers allow
their customers to bring computers back to the shop for servicing or repairs.
Careers.
There are many career opportunities in the computer industry. Computer
engineers are probably the most technically specialized computer experts. Hardware
engineers design the circuits that are engraved on chips, and they develop and
design the wiring that lets information flow smoothly through the computer.
Engineers also design the technical
aspects of memory, file storage, and peripheral equipment.
Computer programmers write the
instructions that make computers operate properly. Systems analysts determine
the most efficient use of computers for a particular situation. They study
entire computer systems— hardware and software—and the purpose a computer is
intended to serve.
Software publishers make up another career
area. People in this field issue programs, write and edit instruction manuals,
and provide technical services for customers.
Many career opportunities in computers
exist outside the computer industry itself. For example, data processors enter
information into computers. Workers in many industries oversee the computers
that control machines.
Some of the industry's most successful
individuals are self-taught. But most computer careers call for a college
degree. College courses that help prepare students for careers in computers
include programming, electronics, systems analysis, and data processing.
The development of the computer
The ideas and inventions of many
engineers, mathematicians, and scientists led to the development of the
computer. The ancient abacus served as the earliest sort of calculating device.
But its use was limited by the need to move each counter individually (see
Abacus).
Early calculating devices. The first true calculating machines were developed in
the 1600's. In 1642, the French mathematician, scientist, and philosopher
Blaise Pascal invented the first automatic calculator. The device performed
addition and subtraction by means of a set of wheels linked to each other by
gears. The first wheel represented the numbers 1 to 10, the second wheel represented
10's, the third stood for 100's, and so on. When the first wheel was turned 10
notches, a gear moved the second wheel forward a single notch. The other wheels
became engaged in a similar manner.
In the early 1670's, the German
mathematician Gottfried Wilhelm von Leibniz extended the usefulness of
Pascal's calculator. Leibniz's improvements included gear and wheel
arrangements that made multiplication and division possible.
Leibniz also sought a counting system that
would be easier for a machine to handle than the decimal system. He developed
the binary system of mathematics in the late 1600's. Binary mathematics uses
only the 0 and the 1 arranging them to represent all numbers.
An important contribution to the
development of binary mathematics was made in the mid-1800's by George Boole,
an English logician and mathematician. Boole used the binary system to invent a
new type of mathematics. Boolean algebra
and Boolean logic perform complex mathematical and logical operations
on the symbols O and 1. Thus, a mechanical representation of binary mathematics
would require the representation of only those two digits. This advance had a
major effect on the development of computer logic and computer languages.
Early punched-card computing devices. A French textile weaver named Joseph Marie Jacquard
made the next great contribution to the development of the computer. In the
weaving process, needles directed thread to produce patterns. In 1801; Jacquard
invented the Jacquard
loom, which used punched cards to automate
this process for the first time. The cards had patterns of holes punched in
them, and were placed between the rising needles and the thread. The presence
or absence of a hole could be compared to the two digits of the binary system.
Where there were holes, the needles rose and met the thread. Where there were
no holes, the needles were blocked. By changing cards and alternating the
patterns of punched holes, it became possible to mechanically create complex
woven patterns.
The punched cards of the Jacquard loom
inspired the English mathematician Charles Babbage. During the 1830's, Babbage
developed the idea of a mechanical computer that he called an analytical engine. He worked on the machine for almost 40 years. When
performing complex computations or a series of calculations, the analytical
engine would store completed sets of punched cards for use in later operations.
Babbage's analytical engine contained all of the basic elements of an
automatic computer—storage, working memory, a system for moving between the
two, and an input device. But the technology of Babbage's time was not advanced
enough to provide the precision parts he needed to construct the machine, and
he lacked funding for the project. Babbage, like others of his time, also
lacked an understanding of the nature and use of electricity.
The first successful computer. In 1888, American inventor and businessman Herman
Hollerith devised a punched card system, including the punching equipment, for
tabulating the results of the United States census (see Census). Hollerith's
machines used electrically charged nails that, when passed through a hole
punched in a card, created a circuit. The circuits registered on another part
of the machine, where they were read and recorded. Hollerith's machines
tabulated the results of the 1890 census in the United States, making it the
fastest and most economical census to date. In a single day, 56 of these
machines could tabulate census information about more than 6 million people.
Hollerith's tabulator enjoyed widespread
success. Governments, institutions, and industries found uses for the machine.
In 1896, Hollerith founded the Tabulating Machine Company. He continued to
improve his machines during the following years. In 1911, he sold his share of
the company. Its name was changed to the Computing-Tabulating-Recording Company
(C-T-R). In 1924, the name was changed to International Business Machines
Corporation (IBM).
The first analog computer. Vannevar Bush, an American electrical engineer, worked
to develop a computer that would help scientists. In 1930, he built a device
called a differential analyser to solve differential equations. This machine was the
first reliable analog computer. It derived measurements from the movements of
its gears and shafts.
The first electronic computers. Some scientists and engineers saw greater computing
potential in electronics. The first special-purpose electronic digital computer
was constructed in 1939 by John V. Atanasoff, an American mathematician and
physicist. In 1944, Howard Aiken, a professor at Harvard University, U.S.A.,
built another early form of digital computer, which he called the Mark I. The
operations of this machine were controlled chiefly by electromechanical relays
(switching devices).
In 1946, two engineers at the University of
Pennsylvania, U.S.A., J. Presper Eckert, Jr., and John William Mauchly, built
the first general-purpose electronic digital computer. They called it ENIAC
(Electronic Numerical Integrator And Computer). ENIAC contained about 18,000
electronic valves, which replaced the relays that had controlled the operation
of Mark I. The machine weighed more than 27 metric tons, occupied more than 140
square metres of floor space, and consumed 150 kilowatts of electricity during
operation. ENIAC operated about 1,000 times as fast as the Mark I. It could
perform about 5,000 additions and 1,000 multiplications per second, and could
store parts of its programming.
Although ENIAC performed its work rapidly,
programming the huge machine took a great deal of time. Eckert and Mauchly
next worked on developing a computer that could store even more of its
programming. They worked with John von Neumann, a Hungarian-born American
mathematician. Von Neumann helped assemble all available knowledge of how the
logic of computers should operate. He also helped outline how stored -
programming techniques would improve computer performance.
In 1951, a computer based on the work of
the three men became operational. It was called EDVAC (Electronic Discrete
loanable Automatic Computer). EDVAC strongly influenced the design of later
computers.
Also in 1951, Eckert and Mauchly invented
a more advanced computer called UNIVAC I (UNIVersal
Automatic Computer). Within a few years, UNIVAC I became the first commercially
available computer. Unlike earlier computers, UNIVAC I handled both numbers and
alphabetical characters equally well. It also was the first computer system
in which the operations of the input and output equipment were separated from
those of the computing unit. UNIVAC I used electronic valves to perform
arithmetic and memory-switching functions.
The first UNIVAC I was installed at the
U.S. Bureau of the Census in June 1951. The following year, another UNIVAC I
was used to tabulate the results of the United States presidential election.
Based on available data, UNIVAC I accurately predicted the election of
President Dwight D. Eisenhower less than 45 minutes after the polls closed.
The miniaturization of computer
components.
The invention of the transistor in 1947
led to the production of faster and more reliable electronic computers.
Transistors control the flow of electric current in electronic equipment. They
soon replaced the bulkier, less reliable electronic valves. In 1958, Control
Data Corporation introduced the first fully transistorized computer, designed
by American engineer Seymour Cray. IBM introduced its first transistorized
computers in 1959.
Miniaturization continued with the
development of the integrated circuit in the early 1960's. An integrated
circuit contains thousands of transistors and other tiny parts on a small
silicon chip. This device enabled engineers to design both minicomputers and
high-speed mainframes with tremendous memory capacities.
Despite the shrinking size of their
components, most computers remained relatively large and expensive. But
dependence on computers increased dramatically. By the late 1960's, many large
businesses relied on computers. Many companies linked their computers together
into networks, making it possible for different offices to share information.
During the 1960's, computer technology
improved rapidly. Different kinds of circuits were placed on silicon chips.
Some of the circuits contained the computer's logic. Other chips held memory.
By the early 1970's, the entire workings of a computer could be placed on a
handful of chips. As a result, smaller computers became possible.
The central chip that controlled the computer became known as a microprocessor.
The personal computer. The first personal computer, the Altair, was
introduced in 1975. Only electronics hobbyists bought these computers.
In 1977, two American students, Steven P.
Jobs and Stephen C. Wozniak, founded the Apple Computer Company and introduced
the Apple II personal computer. The Apple II was much less expensive than mainframes.
As a result, computers became available to people other than computer
specialists and technicians. Personal computers were purchased by small and
medium-sized businesses that could not afford mainframes or did not need the
immense computing power that mainframes provided. Millions of individuals,
families, and schools also bought them.
In 1981, IBM entered the personal computer
market with its PC. The machine was even more successful than the Apple II.
Apple scored another success in 1984 with the introduction of its Macintosh, a
powerful, easy-to- use desktop computer.
As computer power increased, so did
computer speed. These increases were accompanied by a steady reduction in both
size and cost. Modern personal computers are more powerful than UNIVAC I and
can be purchased for less than $1,000.
Computers of the future. Tomorrow's computers will be increasingly powerful. Computer researchers continue to seek ways to develop faster and more powerful
machines and software. Much software research focuses on the further
development of artificial intelligence, which is intended to help computers
make decisions rather than simply to manipulate data. One type of artificial
intelligence, the expert system, translates patterns of experience into
software. An expert system responds to input by asking questions and providing
responses. In this manner, it constantly narrows the field of inquiry until a
solution is achieved.
Much effort also is being devoted to
making computers smaller. In the near future, most experts feel that computers
will continue to be built from integrated circuits. But some scientists
foresee the production of biological computers, which will be grown rather
than manufactured. In addition, some experts believe that computer technology
will develop methods of storing data on individual molecules. A molecular
storage system could contain all of the knowledge of the human race in a space
smaller than a paperback book.
Problems of the computer age
Because computers provide such convenient
storage for large amounts of information, less and less information is stored
on paper. Much of the convenience of computers stems from their ability to form
networks by means of telephone lines. But a computer that makes up part of a
network resembles a room with many doors. Intruders who slip through these
"doors" are difficult to trace. For this reason, computer designers
work to safeguard stored information from unauthorized access, as well as from
system breakdown or failure.
Computers and privacy. Many people fear that their right to privacy is
threatened by the possible misuse or unauthorized disclosure of information in
computer databases. Databases often contain private and personal information,
such as medical, banking, or tax records. Other databases pertain to business
plans or inventions that a company must conceal from competing companies.
Still other databases store top-secret military information or other kinds of
data important to a nation's security. Today, laws control the disclosure of
data.
Computers and security. Computer operating systems are designed to prevent
unauthorized entry into a computer, but computer crimes sometimes occur. Industrial
spies and thieves often use telephone lines to gain access to computers. Some
of these criminals steal or change the information in a computer database. Others
steal money by using the capability of computers to transfer funds
electronically from one account to another. Major problems can result if
someone obtains illegal access to secret information in government or corporate
databases. Sometimes, people within an organization commit computer crimes.
Other crimes are committed by outsiders who create chaos by breaking into
computer systems.
In the late 1980's, computer experts
became aware of a dangerous type of program called a computer virus. A computer virus is designed to do mischief,
sometimes by deleting or changing information and sometimes by simply inserting
a message. A virus eventually enters a computer's operating system. It spreads
by rapidly making copies of itself, thus "infecting" the other
computer systems in a network. This process can quickly overload huge computer
networks.
Various methods help safeguard computer
systems and databases. Protective measures are built into many computer
operating systems to prevent access by invaders. Many computers require a user
to enter a secret password. Some systems automatically scramble information so
that it can only be decoded by authorized personnel. Careful protection of
these passwords and codes helps decrease the likelihood of illegal access.
Other problems. Computers are valuable in many ways. But if a computer
breaks or is damaged, the people who rely on it face great difficulties. Until
the computer is fixed, these people may be worse off than if they never had a
computer at all. For example, information may be lost if a computer system
suffers damage in a natural disaster, such as a fire or flood. Computer
breakdowns and faulty programming in business organizations delay transactions,
disrupt work, and create inconveniences for consumers. An undetected computer
malfunction at an air traffic control centre could cause a collision. A
computer failure at a national defence installation could have even more
serious consequences.
Computers, together with their programs,
are the most complicated machines in history — and, arguably, the most useful.
Modern industrial societies depend on computers in the home, school, and
workplace. As computers become more powerful and widespread, computer
education must continue to increase as well.
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Outline
The importance of the computer
Solving numerical problems
Storing and retrieving information
Creating and displaying documents and
pictures D. Other uses
Basic principles of computers
How a computer operates
Computer hardware and software
Kinds of computers
Embedded computers
Personal computers and workstations C
Mainframes
How a computer works
Entering and encoding data and
instructions
Processing data
Decoding the results and producing output
D. Storing information
Programming a computer
Preparing a program
Using programming languages
The computer industry
Manufacturing
Sales
Research and
Service and repair development
Careers
The development of the computer
Problems of the computer age
Computers and privacy
Other problems
Computers and security
Questions
What is an expert system?
How does the binary system differ from the
decimal system?
What role does the digital logic unit play
in processing?
How do scientists use computers to develop
theories?
What is an operating system?
How has the transistor affected computer
technology?
Personal Computer
A personal computer system. A personal computer system has many uses in businesses
and in the home. The parts that make up such a system vary according to the needs
of the user. The illustration below shows some of the hardware in a basic
personal computer system.
What is a computer virus?
How does a modem work?
Why can mainframes satisfy the needs of
many users at once?
Why did the computer industry's rate of
growth increase dramatically during the late 1970's?
Personal Computer is a desktop or handheld
computer designed for general-purpose use. Personal computers are used by
individuals, families, schools, or companies for such purposes as keeping
records, writing reports, learning a new subject, playing games, programming,
or even running household appliances.
All computers store and handle
information. Many large businesses use large, expensive computers that must be
shared by a number of people to be economical. Personal computers, however,
are smaller than such business computers, because they are equipped with one or
more microprocessors. Microprocessors, which were introduced in 1971, are
miniature electronic devices that can handle many of the same tasks as a large
computer, though more slowly and with smaller amounts of information. The
development of microprocessors led to a reduction in the cost of computers and
thus made it possible for computers to be purchased by individuals, schools,
and small companies.
Uses of a personal computer
Like other computers, personal computers
can be instructed to perform a variety of individual functions. A set of
instructions that tells a computer what to do is called a program.
Today, more than 10,000 application programs are available for use on personal
computers. They include such popular programs as word processing programs, spreadsheet programs,
database programs,
and communication programs.
Word processing programs are used to type,
correct, rearrange, or delete text in letters, memos, reports, and school
assignments. Spreadsheet programs enable individuals to prepare tables easily.
The users of such programs establish rules for handling large groups of numbers.
For example, using a spreadsheet program, a person can enter some numbers into
a table and the program will calculate and fill in the rest of the table. When
the user changes one number in the table, the other numbers will change
according to the rules established by that user. Spreadsheets may be used for
preparing budgets and financial plans, balancing a chequebook, or keeping
track of personal investments.
Database programs allow a computer to
store large amounts of data (information) in a
systematic way. Such data might include the name, address, telephone number,
salary, and starting date of every employee in a company. The computer could
then be asked to produce a list of all employees who receive a certain salary.
Communication programs connect a personal
computer to other computers. People can thereby exchange information with one
another via their personal computers. In addition, communication programs
enable people to link their personal computers with databanks. Databanks are huge collections of information stored
in large centralized computers. News, financial and travel information, and
other data of interest to many users can be obtained from a databank.
Other programs include recreational and
educational programs for playing games, composing and hearing music, and
learning a variety of subjects. Programs have also been written that turn
household appliances on and off. Some people develop their own programs to meet
needs not covered by commercially prepared programs. Others buy personal
computers mainly to learn about computers and howto program them.
Hardware
The physical equipment that makes up a
computer vstem is called hardware. The two most
important nieces of hardware are the primary memory and the nrocessor. The primary memory,
sometimes called the main memory,
stores information and programs in the computer. The processor in a personal
computer is a microprocessor. It carries out programs and transforms
information. Adding or subtracting numbers, arranging text, and producing
pictures and sounds are all ways the processor transforms data. A processor
works very fast.
It can carry out more than 5 million
logical operations in a single second.
Equipment other than the processor and
primary memory is called peripheral hardware,
and the individual devices are sometimes called peripherals. Peripheral hardware includes input devices, output devices, secondary memories, and communication devices.
Input devices are used for entering data
and programs into the computer. A keyboard for typing words and numbers—and
thus entering them into the computer—is one of the most common input devices. A
mouse can also be used to give commands to a computer.
When this handheld box is moved on a flat surface, it causes a pointer to
point at a specific instruction or other data displayed on a computer screen.
Clicking a button on the mouse causes the instruction to be carried out or the
data to be selected for use elsewhere. Other input devices include a joystick
for moving figures about on a screen and a graphic tablet consisting of a pad and a "wired" pen for producing
illustrations.
Output devices let a person get
information from the computer. They include a monitor
(television screen) for showing text and pictures, a printer
for producing data on paper, a plotter for making
drawings, and a speaker for producing sounds.
A secondary memory, also called an auxiliary memory or mass storage, is used for storing data and programs for long
periods of time. Secondary memories are generally bigger and less
expensive—but slower—than the main memory, which is built into the computer
itself.
The two chief kinds of secondary memory
are magnetic disks and magnetic tapes. The disks are much faster than the
tapes. Some disks, called floppy disks
or diskettes, are made of flexible material and can be removed from
the disk drives that operate them. Diskettes can store about 1
million characters (letters or numbers). Other disks, called hard disks, hold tens of millions of characters and generally are
not removable. They are often installed in the same case as the processor. Hard
disks are more expensive than floppy disks, but they are faster and more
convenient. All the computer's programs and other data can be kept on a hard
disk so that they can all be used without having to change disks.
Communication devices connect computers to
one another. These devices include modems, which connect a
computer to a telephone. Modems enable a computer to transmit data to other
computers via telephone lines or other communications networks, and to receive
data from distant computers. Communication devices called local area networks connect computers in the same building directly to
one another. They provide much faster communication than do modems.
Software
The programs that tell various parts of a computer what to do are called software. A program is made
up of many instructions that direct a variety of activities. For example, some
tell the processor to move data from one part of the computer to another, such
as from the keyboard to the primary or secondary memory. Others control how
the computer transforms information. In addition, they tell the computer to
remember as a single new instruction a program made up of many old instructions.
Whenever the new instruction, called a procedure, is used, all the old instructions are carried out.
The instructions used to write a program
make up a programming language. There are several levels of increasingly easy-to-use
programming languages, from machine language
through assembly language to higher level languages.
Fligher level languages are easy to use because they allow the user to give the
computer such commands as draw a circle, move this paragraph, or print this letter.
For more information on programming languages, see Computer (Programming a
computer).
How to choose a personal computer
The chief factors involved in the
selection of a personal computer are the buyer's needs and budget. For
example, before choosing a personal computer, you need to know whether you plan
to use it mainly for one purpose—such as word processing—or for many different
purposes. Different software is available for different types of computers, and
so the types of functions a particular computer can perform vary. In addition,
the amount of memory in the computer determines the length of a program that a
computer can handle as well as the speed with which the computer will work. If
you wish to run useful programs, you will need a computer with a memory of at
least 256K. Such a computer is able to store more than 256,000 characters in
primary memory. For more specialized programs, you may need as many as 1
million characters in primary memory.
Needs and budget also influence the
selection of the peripheral hardware. A computer system that uses a home
television screen will be less expensive than one with its own monitor screen.
A television screen, however, will not be as clear or show as much text as a
monitor. Also, if you want to draw pictures or graphs, you should choose a
computer and screen that can handle graphics and perhaps colour.
To get a paper copy of work done by the
computer, you will need a printer. Inexpensive printers are slow, printing
about 30 characters per second. The printed copy may also be hard to read.
Letter-quality printers can be faster and can produce better-quality copy than
other printers, but are more expensive.
If you plan to write long reports or wish
to handle a large amount of data, you should have a two-diskette system.
Copying information and programs from one diskette to another is much easier
and faster with this system. Or, you may decide to buy a computer with a hard
disk for handling large amounts of data.
To send electronic mail to other computer
users or to use information from databanks, you will need a modem. Modems vary
in cost and in the speed at which they transmit information.
During the 1940's, scientists developed
the transistor, a tiny device that controls electronic signals. By the
early 1960's, researchers had succeeded in building integrated circuits by
arranging thousands of transistors and other electronic parts on tiny slices of
silicon called silicon chips. The first microprocessors were produced in 1971. The
development of microprocessors made small, inexpensive microcomputers such as personal computers possible.
Electronic games played with a television
set provided one of the first popular uses for microcomputer technology.
During the early 1970's, manufacturers began selling personal computers. See also Computer; Integrated circuit;
Microprocessor.
Computer graphics are images created by a computer. These images
include diagrams, cartoon animations, and even highly realistic pictures. The
process by which computers draw, colour, shade, and manipulate images is also
known as computer graphics. Computer graphics enable us to gather, display, and
understand information quickly and effectively. Computer graphics can even
produce images of objects and processes that we have no other way of seeing,
such as the inside of a molecule or the operation of a black hole.
Computer graphics have numerous uses in a
wide variety of fields. Businesses follow sales from charts and graphs made by
computers. Computer graphics help engineers create and test designs for such
products as cars and aircraft. Through computer graphics, architects can view
building designs drawn in three dimensions from any angle. Scientists use
computer graphics to design new drug molecules, track weather systems, and
test theories that describe how galaxies develop. Doctors use computer images
of the inside of the body to locate tumours and other disorders and plan
treatment (see Computerized tomography (CT)). Computer graphics are also used
in art, in the production of cartoons and special effects in films, and in
video games.
Computer graphics are created on a
computer display screen, which resembles a television screen. The screen
consists of thousands of tiny dots called picture elements, or pixels. You can see individual pixels by looking closely at the letters that
appear on a computer screen. A computer can turn each pixel on and
off like a light bulb to make a pattern. Different combinations of pixels can
produce any picture we want.
All computers need a program that
tells them what to do. A computer graphics program directs the drawing on
a computer's screen. The program may generate the image itself or it may copy
an image from another source. For example, a program that draws molecules might
start by solving equations that describe molecular structure. It can then use
the solutions to display the shape of a molecule. But a program that copies a
photograph might first convert points on the image into a list of numbers. The
numbers can then instruct the computer which pixels to turn on and off. See
also Computer (The importance of the computer).
Computerized tomography (CT) is an
X-ray system used to produce images of various parts of the body, such as the
head, heart, and abdomen. Doctors use CT images to help diagnose and treat
diseases. The technique is also called computer tomography or computerized axial tomography
(CA T).
To produce a CT image, the patient lies on
a table that passes through a circular scanning machine called a gantry. The
table is positioned so that the organ to be scanned lies in the centre of the
gantry. A tube on the gantry beams X rays through the patient's body and into
special detectors that analyse the image produced. The gantry rotates around
the patient to obtain many images from different angles. A computer then
processes the information from the detectors to produce a cross sectional image on a video screen. By
moving the table in the gantry, doctors can obtain many scans of the same organ
or even the entire body.
Sometimes an iodine solution, called a contrast agent, is injected into the body to make certain organs show up clearly in the
CT scan. For scans of the abdomen and pelvis, the patient drinks a barium
mixture (which is opaque to X rays) to outline the inner surfaces of the
stomach and bowel.
Doctors use CT scans to diagnose many conditions, such as tumours, infections, blood clots, and broken bones. CT also assists in treating some diseases that might otherwise require surgery. For example, doctors can use a CT scan to guide catheters (small tubes) to an abscess in the body and drain pus from the infected area. See also Radiology; X ray.
Doctors use CT scans to diagnose many conditions, such as tumours, infections, blood clots, and broken bones. CT also assists in treating some diseases that might otherwise require surgery. For example, doctors can use a CT scan to guide catheters (small tubes) to an abscess in the body and drain pus from the infected area. See also Radiology; X ray.
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