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        Before the early 1980s, computers were unknown to the average person. Many people had

never even seen a computer, let alone used one. The few computers that existed were relatively large,

bulky devices confined to secure computer centers in corporate or government facilities. Referred to as

mainframes, these computers were maintenance intensive, requiring special climate-controlled

conditions and several full-time operators for each machine. Because early mainframes were expensive

and difficult to operate, usage was restricted to computer programmers and scientists, who used them

to perform complex operations, such as processing payrolls and designing sophisticated military


        Beginning in the early 1980s, the computer world changed dramatically with the introduction of

microcomputers, also called personal computers (PCs). These relatively small computers were

considerably more affordable and much easier to use than their mainframe ancestors. Within a few

years, ownership of personal computers became widespread in the workplace, and today, the personal

computer is a standard appliance in homes and schools.

        Today’s computers come in a variety of shapes and sizes and differ significantly in computing

capability, price, and speed. Whatever their size, cost, or power, all computers offer advantages over

manual technologies in the areas of speed, accuracy, versatility, storage capabilities, and

communications capabilities.


        Computers operate with lightening-like speed, and processing speeds are increasing as

computer manufacturers introduce new and improved models. Contemporary personal computers are

capable of executing billions of program instructions in one second. Some larger computers, such as

supercomputers, can execute trillions of instructions per second, a rate important for processing huge
amounts of data involved in forecasting weather, monitoring space shuttle flights, and managing other

data-intensive applications.


        People sometimes blame human errors on a computer. In truth, if a computer user enters

correct data and uses accurate programs, computers are extremely accurate. A popular expression

among computers professionals is “garbage in—garbage out” (GIGO), which means that if inaccurate

programs and/or data are entered into a computer for processing, the resulting output will also be

inaccurate. The computer user is responsible for entering data correctly and making certain that

programs are correct.


        Computers are perhaps the most versatile of all machines or devices. They can perform a variety

of personal, business, and scientific applications. Families use computers for entertainment,

communications, budgeting, online shopping, completing homework assignments, playing games, and

listening to music. Banks conduct money transfers, account withdrawals, and the payment of checks via

computer. Retailers use computers to process sales transactions and to check on the availability of

products. Manufacturers can manage their entire production, warehousing, and selling processes with

computerized systems. Schools access computers for keeping records, conducting distance learning

classes, scheduling events, and analyzing budgets. Universities, government agencies, hospitals, and

scientific organizations conduct life-enhancing research using computers. Perhaps the most ambitious

such computer-based scientific research of all time is the Human Genome Project. Completed in April of

2003, this program was more than two years ahead of schedule and at a cost considerably lower than

originally forecast. This project represented an international effort to sequence three billion DNA

(deoxyribonucleic acid) letters in the human genome, which is the collection of gene types that comprise
every person. Scientists from all over the world can now access the genome database and use the

information to research ways to improve human health and fight disease.


          Storage is a defining computer characteristic and is one of the features that revolutionized early

computing, for it made computers incredibly flexible. A computer is capable of accepting and storing

programs and data. Once stored in the computer, a user can access a program again and again to

process different data. Computers can store huge amounts of data in comparably tiny physical spaces.

For example, one compact disk can store about 109,000 pages of magazine text, and the capacities of

internal storage devices are many times larger.


          Most modern computers contain special equipment and programs that allow them to

communicate with other computers through telephone lines, cable connections, and satellites. A

structure in which computers are linked together using special programs and equipment is a network.

Newer communications technologies allow users to exchange information over wireless networks using

wireless devices such as personal digital assistants (PDAs), notebook computers, and cell phones.

          A network can be relatively small or quite large. A local area network (LAN) is one confined to a

relatively small geographical area, such as a building, factory, or college campus. A wide area network

(WAN) spans a large geographical area and might connect a company’s manufacturing plants dispersed

throughout North America. Constant, quick connections along with other computer technologies have

helped boost productivity for manufacturers.

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