A computer is a machine that can be programmed
to manipulate symbols. Its principal characteristics are:
§ It responds to a specific set of instructions
in a well-defined manner.
§ It can execute a prerecorded list of
instructions (a program).
§ It can quickly store and retrieve large amounts
of data.
Therefore computers can perform complex and
repetitive procedures quickly, precisely and reliably. Modern computers are
electronic and digital. The actual machinery (wires, transistors, and circuits)
is called hardware; the instructions and data are called software. All
general-purpose computers require the following hardware components:
§ Central processing unit (CPU): The heart of the
computer, this is the component that actually executes instructions organized
in programs ("software") which tell the computer what to do.
§ Memory (fast, expensive, short-term memory):
Enables a computer to store, at least temporarily, data, programs, and
intermediate results.
§ Mass storage device (slower, cheaper, long-term
memory): Allows a computer to permanently retain large amounts of data and
programs between jobs. Common mass storage devices include disk drives and tape
drives.
§ Input device: Usually a keyboard and mouse, the
input device is the conduit through which data and instructions enter a
computer.
§ Output device: A display screen, printer, or
other device that lets you see what the computer has accomplished.
In addition to these components, many others
make it possible for the basic components to work together efficiently. For
example, every computer requires a bus that transmits data from one part of the
computer to another.
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