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What is a Computer?
• A computer is a programmable machine.
• A device that computes, especially a programmable electronic
machine that performs high-speed mathematical or logical
operations or that assembles, stores, correlates, or otherwise
• A programmable machine that performs high-speed
processing of numbers, as well as of
text, graphics, symbols, and sound. All computers contain a
central processing unit that interprets and executes
instructions; input devices, such as a keyboard and a
mouse, through which data and commands enter the
computer; memory that enables the computer to store
programs and data; and output devices, such as printers and
display screens, that show the results after the computer has
Basic Parts of a Desktop
The basic parts of a desktop
computer are the computer
case, monitor, keyboard, mouse, a
nd power cord. Each part plays
an important role whenever you
use a computer.
The computer case is the metal
and plastic box that contains the
main components of the
computer. It houses the
motherboard, central processing
unit (CPU), the power supply, and
The system unit is the core of a computer
system. Usually it's a rectangular box
placed on or underneath your desk. Inside
this box are many electronic components
that process information.
The monitor works with a video
card, located inside the computer
case, to display images and text on
the screen. Newer monitors usually
have LCD (liquid crystal display)
or LED (light-emitting diode)
displays. These can be made very
thin, and they are often called flat
panel displays. Older monitors
use CRT(cathode ray tube) displays.
CRT monitors are much bigger and
heavier, and they take up more
The power cord is
the link between the power
outletand the power supply
unit in the computer casing. If
the power cord is not plugged
in, the computer will not power
on. To protect your computer
from voltage spikes, you can plug
the power cord into a surge
protector. You can also use
an Uninterruptable Power
Supply (UPS), which acts as a
surge protector and also provides
temporary power if there is a
The keyboard is one of the primary
ways we communicate with the
computer and enter data.
• The keys on your keyboard can be divided into several groups based
• Typing (alphanumeric) keys. These keys include the same
letter, number, punctuation, and symbol keys found on a traditional
• Control keys. These keys are used alone or in combination with
other keys to perform certain actions. The most frequently used
control keys are Ctrl, Alt, the Windows logo key , and Esc.
• Function keys. The function keys are used to perform specific tasks.
They are labeled as F1, F2, F3, and so on, up to F12. The
functionality of these keys differs from program to program.
• Navigation keys. These keys are used for moving around in
documents or webpages and editing text. They include the arrow
keys, Home, End, Page Up, Page Down, Delete, and Insert.
• Numeric keypad. The numeric keypad is handy for entering numbers
quickly. The keys are grouped together in a block like a conventional
calculator or adding machine.
• The following illustration shows how these keys are arranged on a
typical keyboard. Your keyboard layout might be different.
• Caps Lock Key
The caps lock key activates a feature that affects only the letter
keys. Pressing on the caps lock button causes all letter keys to type in uppercase. All
other keys will act the same as if caps lock is off. To deactivate caps lock, press the
caps lock key again.
• Shift Key The shift key is used in combination with a second key. The shift key is used
primarily to capitalize letters. Shift differs from caps lock because you have to hold the
shift key down while simultaneously pressing another key to capitalize a letter, where
you only press the caps lock key once. Holding down the shift key also is used to type
the characters and symbols above the numbers on the number keys.
• Tab Key
• The tab key is used to move from one position on the screen to another. It also
creates a “tab stop” (right 1/2 inch) indentation for your paragraphs. This is very
similar to a typewriter.
• Enter Key When working with text (words), pressing on the enter key moves the
cursor down to the next line. Otherwise, pressing the enter key will activate anything
that you have selected.
• Escape Key
The escape key is used to cancel the current operation or can be
used to exit a program.
Note: The Cursor is a blinking line when typing a letter that lets you know where you will
start typing. (It moves as you type and looks like “|” )
• Space Bar
Pressing the space bar while the cursor is positioned within
text will cause a space (one character wide) to be placed at the position of
the cursor (like on a typewriter).
• Control Key
The control key (Ctrl) is usually used with another key.
Holding the control key in addition to another key or keys will start a
function. Later on, we will teach you some control key functions that deal
with word processing.
• Alt Key
The alternate key (Alt), similar to the control key, and is
used in combination with other keys.
• Arrow Keys
The four arrow keys are located on several keys to the right
of the spacebar at the bottom of the keyboard. Pressing one of these keys
will cause some type of screen movement in the direction of the arrow on
the key. These keys are frequently used when correcting mistakes in
documents and allow users to “go back” and fix mistakes instead of erasing
all of the work since the mistake was made.
• Backspace Key Pressing the backspace key while the cursor is positioned
within text will delete the character (or space) immediately to the left of the
• Delete Key
Pressing the delete key while the cursor is positioned within
text will delete the character (or space) immediately to the right of the
The mouse is a peripheral that is
known as apointing device. It
lets you point to objects on the
screen, click on
them, and move them.
There are two main types of
mice: optical and mechanical.
The optical mouse uses an
electronic eye to detect
movement and is easier to clean.
The mechanical mouse uses a
rolling ball to detect movement.
Generally, a mechanical mouse is
cheaper, although it may require
regular cleaning to keep it
Traditionally, a mouse connects
to the computer using
a USB or PS/2 connection.
However, you can also buy
a wireless mouse, which can
reduce clutter on your desktop.
Basic parts of a Mouse
• A mouse typically has two buttons: a primary button (usually
the left button) and a secondary button (usually the right
button). You will use the primary button most often. Most
mice also include a scroll wheel between the buttons to help
you scroll through documents and webpages more easily. On
some mice, the scroll wheel can be pressed to act as a third
button. Advanced mice might have additional buttons that can
perform other functions.
• Because the mouse is a critical component of the
computer, we’ll examine some mouse techniques
that will be used.
• The mouse can be used in many different ways.
There are primarily the two mouse buttons, known
as the left and right button. The left button is
primarily used. Some mouse techniques include:
• Click: This is the easiest of the techniques, however it is very
important that you do it properly. To click, you press down one
of the mouse buttons. As you click it, it makes a “clicking”
noise. The most important skill to learn when clicking is that it
only takes a very light, short tap to click a mouse button. Don’t
click the mouse too hard since this tends to slow you down.
Once you have mastered clicking, you will be ready to move
on to the next most essential practice, pointing.
• Left Clicking: This is the primary “click” that you will use. This
is clicking on the left mouse button. When someone
says, “click here,” that usually means to left click.
• Right Clicking: This is used to change options or perform
specific functions that aren’t usually necessary for beginner.
• Point: Use the mouse to move the mouse pointer so that it
hovers over the top of an icon or word on the screen.
Sometimes, this is all that you need to do in order to prompt a
response from the computer (as an example, the shape of
your cursor may change).
Point and click: Move the mouse pointer over the top of an item (such
as an icon) on your screen and then (while holding your hand still)
gently press and release the left button on the mouse. This technique
is often used to make a selection.
Double-click: While hovering the mouse pointer over an item on the
screen, quickly press the left mouse button two times. This may take
some practice but it is a very useful and important skill. If you are
having problems double clicking, it’s most likely because you’re moving
the mouse slightly when double clicking. Try to steady your hand and
try it again. By double clicking, you are usually prompting the
computer to take an action on the item you selected (double clicking
on an icon on your computer desktop may open or start a program).
Click and drag: Press and hold down a mouse button (usually the left
button). As you hold down the button, move the mouse in any
direction. Click and drag is a method used when “highlighting” or
“selecting” text. To do this to text, click at the beginning of the text
that you want to select, hold down the left mouse button, and move
your mouse to the end of where you want to highlight.
A printer transfers data from a computer onto paper. The two main
types of printers are inkjet printers and laser printers. Inkjet printers
are the most popular printers for the home. They can print in black and
white or in full color and can produce high-quality photographs when
used with special paper. Laser printers are faster and generally better
able to handle heavy use.
Inkjet printer (left); laser printer (right)
Speakers are used to play sound.
They can be built into the system
unit or connected with cables.
Speakers allow you to listen to
music and hear sound effects from