Module 1: Computer Basics

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Lesson 1 Topic 2 Parts of a Computer

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Parts of a Computers

Parts of a Computers

A computer has various parts, and each part performs a specific function.
The following tables describe the parts of a computer. Click on an item in
the list below for a description.

* Input devices [2] [3]
* Output devices [4]
* Central processing unit and memory [5]
* Motherboard [6]
* Expansion cards [7]
* Storage devices [8]
* Ports and connections [9]

Input devices

You use input devices to provide information to a computer, such as
typing a letter or giving instructions to a computer, to perform a task.
Some examples of input devices are described in the following list.


A device that you use to interact with items displayed on the computer
screen. A standard mouse has a left and a right button. You use the left
button to select items and provide instructions by clicking an active area
on the screen. You use the right button to display commonly used menu items
on the screen.



A set of keys that resembles a keyboard on a typewriter. You use the
keyboard to type text such as letters or numbers into the computer.



A device that you can use to talk to people in different parts of the
world. You can record sound into a computer by using a microphone. You can
also record your speech and let the computer convert it into text.



A device that is similar to a photocopy machine. You can use this device
to transfer an exact copy of a photograph or document into a computer. A
scanner reads a page and translates it into a digital format that a
computer can read. For example, you can scan photographs of your family
using a scanner.



A device that is similar to a video camera. It allows you to capture and
send live pictures to other users. For example, a webcam allows your
friends and family to see you when you are communicating with them.



A pointing device, similar to a pen, used to make selections and enter
information by tapping on a touch sensitive surface. For example, to enter
information on a personal digital assistant (PDA), you use a stylus. A PDA
is a lightweight, palmtop computer.



A pointing device that is an alternative to a mouse. A trackball
consists of a ball that is rotated to move the pointer on a computer
screen. You can use a trackball when you have limited desk space.


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Output devices

You use output devices to get feedback from a computer after it performs
a task. Some examples of output devices are described in the following


A device that is similar to a television. It is used to display
information in visual form, using text and graphics.



A device that you use to transfer text and images from a computer to a
paper or to another medium, such as a transparency film. You can use a
printer to create a paper copy of whatever you see on your monitor.



A device that allows you to hear sounds. Speakers may either be external
or built into the computer.


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Central processing unit and memory

The central processing unit (CPU) is a device that interprets and runs
the commands that you give to a computer. It is the control unit of a
computer. The CPU is also referred to as the processor. Memory is where
information is stored and retrieved by the CPU. There are three main types
of memory.

Random access memory (RAM)

It is the main memory and allows you to temporarily store commands and
data. The CPU reads data and commands from RAM to perform specific tasks.
RAM is volatile, which means it is available only while the computer is
turned on. The contents of RAM must be copied to a storage device if you
want to save the data in the RAM.

[Random access memory]

Read only memory (ROM)

It is the memory that retains its contents even after the computer is
turned off. ROM is nonvolatile, or permanent, memory that is commonly used
to store commands, such as the commands that check whether everything is
working properly.

[Read only memory]

Flash memory

It is a nonvolatile memory that retains data even after a computer is
turned off. Unlike in ROM, you can erase or modify stored information.

[Flash memory]

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The motherboard is the main circuit board inside a computer. It has tiny
electronic circuits and other components on it. The motherboard connects
input, output, and processing devices together and tells the CPU how to
run. Other components on the motherboard are the video card, the sound
card, and the circuits that allow a computer to communicate with devices
like a printer. The motherboard is sometimes called a system board.


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Expansion Cards

An expansion card is a circuit board that can be attached to a
motherboard to add features such as video display and audio capability to
your computer. An expansion card improves the performance of your computer
and enhances its features. Expansion cards are also called expansion
boards. Some types of expansion cards are described in the following list.

Video card

It is connected to a computer monitor and is used to display information
on the monitor.

[Video card]

Network interface card (NIC)

It allows a computer to be connected to other computers so that
information can be exchanged between them.

[Network interface card]

Sound card

It converts audio signals from a microphone, audio tape, or some other
source to digital signals, which can be stored as a computer audio file.
Sound cards also convert computer audio files to electrical signals, which
you can play through a speaker or a headphone. You connect microphone and
speakers to a sound card.

[Sound card]

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Storage devices

You use storage devices to store computer information. Storage devices
come in many forms. Some examples are hard drive or disk, CD-ROM, floppy
disk, and DVD-ROM. Storage devices can be divided into two types, internal
storage devices and external storage devices. Some common storage devices
are described in the following list.

Hard disk

A magnetic disk that is usually the main storage device on most
computers. It can be an external or an internal device.

[Hard disk]

Floppy disk

A portable storage device that allows you to store a small amount of
data. A disadvantage of this disk is that it can be easily damaged by heat,
dust, or magnetic fields.

[Floppy disk]


A portable storage medium that allows you to store 400 times more data
than on a floppy disk. It is less prone to damage than a floppy disk.



A portable storage medium that is similar to a CD-ROM; however, it can
store larger amounts of data than a floppy disk or a CD-ROM. A DVD-ROM is
commonly used to store movies and videos.


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Ports and connections

A port is a channel through which data is transferred between
input/output devices and the processor. There are several types of ports
that you can use to connect a computer to external devices and networks.
Some types of ports are described in the following list.

Universal serial bus (USB) port

You use this to connect peripheral devices such as a mouse, a modem, a
keyboard, or a printer to a computer.

[Universal serial bus port]


You use this to connect devices such as a digital camera. It is faster
than a USB.


Network port

You use this to connect a computer to other computers to exchange
information between the computers.

[Network port]

Parallel port and serial port

You use these ports to connect printers and other devices to a personal
computer. However, the USB port is now preferred to connect peripheral
devices because it is faster and easier to use.

[Parallel port]

Display adapter

You connect a monitor to a display adapter on your computer. The display
adapter generates the video signal received from a computer, and sends it
to a monitor through a cable. The display adapter may be on the
motherboard, or on an expansion card.



A motherboard and other components inside a computer use direct current
(DC). A power supply takes alternating current (AC) from a wall outlet and
converts it into DC power.


[2] http://alison.com/#inputdeviceTable
[3] http://alison.com/#outputdeviceTable
[4] http://alison.com/#outputdeviceTable
[5] http://alison.com/#cpudeviceTable
[6] http://alison.com/#motherboardTable
[7] http://alison.com/#expansioncardsTable
[8] http://alison.com/#storagedevicesTable
[9] http://alison.com/#portsTable
[10] http://alison.com/#deviceList-amr
[11] http://alison.com/#deviceList-amr
[12] http://alison.com/#deviceList-amr
[13] http://alison.com/#deviceList-amr
[14] http://alison.com/#deviceList-amr
[15] http://alison.com/#deviceList-amr