Microsoft Office Tutorials and References
In Depth Information
COM 8
ESSENTIAL INTRODUCTION TO COMPUTERS
SYSTEM UNIT
The system unit (Figure 9) is a case that contains electronic components of the computer used to
process data. System units are available in a variety of shapes and sizes. The case of the system
unit, also called the chassis, is made of metal or plastic and protects the internal electronic parts
from damage. The motherboard , sometimes called a system board, is the main circuit board of
the system unit. Many electronic components attach to the motherboard, such as the processor,
memory, and expansion slots. The sound card and video card shown in Figure 9 are examples of
adapter cards, which allow a user to enhance the computer system with add-on products.
Processor
The processor (bottom right in Figure 9), also called the central processing unit CPU ), interprets (
and carries out the basic instructions that operate a computer. The processor is made up of the
control unit and arithmetic/ logic unit (Figure 3 on page COM 4). The control unit interprets the
instructions. The arithmetic/logic unit performs the logical and arithmetic processes. High-end
processors contain over 200 million transistors and are capable of performing some operations
10 million times in a tenth of a second, or in the time it takes to blink your eye.
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Processor
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Processor.
Memory
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Memory
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Memory.
Memory , also called random access memory ,or RAM , consists of electronic components that
temporarily store instructions waiting to be executed by the processor, data needed by those
instructions, and the results of processed data (information). Memory consists of chips on a
memory module (lower left of Figure 9) that fits in a slot on the motherboard in the system unit.
The amount of memory in computers typically is measured in kilobytes, megabytes, or
gigabytes. One kilobyte K or KB ) equals approximately 1,000 memory locations and one megabyte (
MB) equals approximately one million memory locations. One gigabyte GB) equals
approximately one billion memory locations. A memory location ,or byte , usually stores one character
such as the letter A. Therefore, a computer with 512 MB of memory can store approximately 512
million characters. One megabyte can hold approximately 500 letter-size pages of text information
and one gigabyte can hold approximately 500,000 letter-size pages of text information.
FIGURE 9 The system unit on a
typical personal computer consists
of numerous electronic components,
some of which are shown in this
figure. The sound card and video
card are two types of adapter cards.
sound card
drive bays
video card
power supply
memory
processor
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