b. The components of a computer consist of devices through which data is entered into the
computer. Processing of data on a computer is performed by specific equipment that is often
referred to as computer "hardware." This equipment consists of:
(1) Input devices, which are used to enter data into a computer. A common input
device is the keyboard. As the data is entered or keyed, it is displayed on a screen (monitor) and
stored in the computer.
(2) A processor unit that contains the electronic circuits that actually cause the
processing of data to occur. All arithmetic and logical data processing takes place in the
processor. Numeric calculations (such as addition, subtraction, multiplication, and division) are
called arithmetic operations. Comparisons of data to see if one value is greater than, equal to, or
less than another are called logical operations. The processor is sometimes called the central
processing unit or CPU. Main memory, also called primary storage, is a part of the processor
unit. Main memory electronically stores data and program instructions when they are being
processed.
(3) Output devices that can be presented in many forms. Where the computer is used
for business applications or business-related personal applications, the two most commonly used
output devices are the printer and the computer screen. Other frequently used names for the
screen are the monitor or the CRT, which stands for cathode ray tube.
(4) Auxiliary storage units which store instructions and data when they are not being
used by the processor unit. A common auxiliary storage device on personal computers is a disk
drive, which stores data as magnetic spots on a small plastic disk called a diskette or floppy disk.
Another auxiliary storage device is called a hard disk drive. Hard disk drives contain
nonremovable metal disks and provide larger storage capacities than floppy disk drives. Each
computer component plays an important role. The processing unit is where the actual processing
of data occurs. The input devices, output devices, and auxiliary storage units that surround the
processing unit are sometimes referred to as peripheral devices. Below is an illustration of the
components of a computer (Figure 5).
PROCESSOR CPU
INPUT
OUTPUT
MAIN MEMORY
AUXILIARY
STORAGE
Figure 3-5. Computer components.
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