Computer
is a device that processes information with astonishing speed and accuracy. Computers
process information by helping to create it and by displaying it, storing
it, reorganizing it, calculating with it, and communicating it to other computers. Computers can
process numbers, words, still pictures, moving pictures, and sounds. The
most powerful computers can
perform tens of billions of calculations per second.
The computer has changed the way we work, learn,
communicate, and play. Virtually every kind of organization throughout the
world conducts business with computers. Students, teachers, and research
scientists use the computer as a learning tool. Millions of individuals and
organizations communicate with one another over a network of computers
called the Internet. Computer
games entertain people of all
ages.
Almost all computers are electronic digital computers.
They are electronic in their use of electric current (a flow of electric
charge) to carry information. They are digital in that they process
information as units of electric charge representing numbers. The word
digital means having to do with numbers.
To enable a computer to process information that is not
numerical–such as words, pictures, or sounds–the computer or some other
device must first digitize that information. A device digitizes information
by translating it into charges that represent numbers. After the computer
processes the digitized information by working with the charges, the
computer or a device connected to the computer translates its results back
into their original form.
Thus, an artist might use a machine called a scanner to
digitize a photograph. The artist would next process the resulting electric
charges in a computer to change the photograph–perhaps to add a border. The
artist would then use a printer connected to the computer to produce a copy
of the altered photo.
Digital computers are one of two general kinds of
computers. The other kind are calculating devices called analog computers.
An analog computer represents amounts with physical quantities, such as
distances along a scale, rather than with numbers. The remainder of this
article deals with digital computers. For more information on analog
computers. The technology of computer hardware (the physical parts of
computer systems) has advanced tremendously since 1946, when the first
electronic digital computer was built. That machine filled a huge room.
Today, a single microprocessor, a device the size of a fingernail, can do
the same work as that pioneering machine.
The technology of software (programs, or sets of
computer instructions and information) is also advancing rapidly. Early
users of computers wrote their own software. Today, most users buy programs
created by companies that specialize in writing software. Hundreds of
thousands of different programs are available for businesses and
individuals. Because of advances in hardware and software, the price of
computing has dropped sharply. As a result, the number of computers in
operation has risen rapidly ever since the first commercial digital
computers were manufactured in the 1950′s. More than 10,000 computers were
in operation worldwide by 1961. Ten years later, the number exceeded
100,000. By 1990, about 100 million computers were running. By the
mid-1990′s, the number had reached about 200 million. |