1.introduction to computers

Introduction to Computers

1

What Is A Computer?

A computer is an electronic device, operating
under the control of instructions (software)
stored in its own memory unit, that can accept
data (input), manipulate data (process), and
produce information (output) from the
processing. Generally, the term is used to
describe a collection of devices that function
together as a system.

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Charles Babbage - 1792-1871
 Difference Engine c.1822
Analytical Engine
 huge calculator, never
finished
 Analytical Engine 1833
 could store numbers
 calculating “mill” used
punched metal cards for
instructions
 powered by steam!
 accurate to six decimal places

Devices that comprise a computer system
Monitor Speaker
(output) (output) System unit
(processor, memory…)

Printer
(output)

Storage devices
(CD-RW, Floppy,
Hard disk, zip,…)
Mouse
(input)
Scanner Keyboard
(input) (input)

4

What Does A Computer Do?

Computers can perform four general
operations, which comprise the information
processing cycle.

 Input
 Process

 Output

 Storage

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Data and Information
 All computer processing requires data, which is a collection of
raw facts, figures and symbols, such as numbers, words,
images, video and sound, given to the computer during the input
phase.
 Computers manipulate data to create information. Information
is data that is organized, meaningful, and useful.
 During the output Phase, the information that has been created
is put into some form, such as a printed report.
 The information can also be put in computer storage for future
use.

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Why Is A Computer So Powerful?
 The ability to perform the information
processing cycle with amazing speed.
 Reliability (low failure rate).
 Accuracy.
 Ability to store huge amounts of data and
information.
 Ability to communicate with other computers.

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How Does a Computer Know
what to do?
 It must be given a detailed list of instructions,
called a compute program or software,
that tells it exactly what to do.
 Before processing a specific job, the
computer program corresponding to that job
must be stored in memory.
 Once the program is stored in memory the
computer can start the operation by executing
the program instructions one after the other.
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What Are The Primary
Components Of A Computer ?
 Input devices.
 Central Processing Unit
(containing the control
unit and the
arithmetic/logic unit).
 Memory.
 Output devices.
 Storage devices.

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Input Devices
 Keyboard.
 Mouse.

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The Keyboard
The most commonly used input device is the
keyboard on which data is entered by
manually keying in or typing certain keys. A
keyboard typically has 101 or 105 keys.

11

The Mouse
Is a pointing device which is used to control
the movement of a mouse pointer on the
screen to make selections from the screen. A
mouse has one to five buttons. The bottom of
the mouse is flat and contains a mechanism
that detects movement of the mouse.

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The Central processing Unit
The central processing unit (CPU) contains
electronic circuits that cause processing to
occur. The CPU interprets instructions to the
computer, performs the logical and arithmetic
processing operations, and causes the input
and output operations to occur. It is
considered the “brain” of the computer.

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Memory
Memory also called Random Access Memory
or RAM (temporary memory) is the main
memory of the computer. It consists of
electronic components that store data
including numbers, letters of the alphabet,
graphics and sound. Any information stored in
RAM is lost when the computer is turned off.

Read Only Memory or ROM is memory that
is etched on a chip that has start-up
directions for your computer. It is permanent
memory.
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Amount Of RAM In Computers
The amount of memory in computers is
typically measured in kilobytes or megabytes.
One kilobyte (K or KB) equals approximately
1,000 memory locations and one megabyte
(M or MB) equals approximately one million
locations A memory location, or byte, usually
stores one character.
Therefore, a computer with 8 MB of memory
can store approximately 8 million characters.
One megabyte can hold approximately 500
pages of text information.

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Output Devices
Output devices make the information resulting
from the processing available for use. The
two output devices more commonly used are
the printer and the computer screen.

The printer produces a hard copy of your
output, and the computer screen produces a
soft copy of your output.

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Storage Devices
Auxiliary storage devices are used to store
data when they are not being used in
memory. The most common types of auxiliary
storage used on personal computers are
floppy disks, hard disks and CD-ROM drives.

17

Computer Software
Computer software is the key to
productive use of computers.
Software can be categorized into
two types:

 Operating system software
 Application software.

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Operating System Software
Operating system software tells the computer
how to perform the functions of loading,
storing and executing an application and how
to transfer data.
Today, many computers use an operating
system that has a graphical user interface
(GUI) that provides visual clues such as icon
symbols to help the user. Microsoft Windows
7 is a widely used graphical operating
system. DOS (Disk Operating System) is an
older but still used operating system that is
text-based.
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Application Software
Application Software consists of programs
that tell a computer how to produce
information. Some of the more commonly
used packages are:

 Word processing
 Electronic spreadsheet
 Database
 Presentation graphics

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1.introduction to computers

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1.introduction to computers