Peripherals
The term peripherals refers to all hardware devices
that are attached to your computer and are controlled
by your computer system
Peripherals can be classified into input devices and
output devices.
Some can be both an input device and an output
device
Input Devices
An input device is a piece of equipment that
enables data to be entered into a computer for
example:

Keyboard
 Mouse
 Joystick

Graphics Tablet
 Digital Camera
 Scanner
Keyboards
The keyboard is made up of push-button
switches which send a signal to the CPU each
time you press them.
Keyboard standards vary with names like
Deluxe, Natural and Cordless.
Mouse
A roller mouse has a ball that is rolled as the mouse
is moved about on the desktop.
Pointing and clicking allows operations to be
performed without having to remember complicated
keyboard commands.
Optical mice are superseding ball mice and use a
light instead of a ball.
Digital Cameras
Allow us to capture images and transfer them
to a computer in the form of an image file.
Image quality is measured in pixels.
Some digital cameras can capture small
amounts of video.
Scanners
Scanners allow us to capture an image or text
and convert it into digital form.
Optical Character Recognition (OCR)
software converts the picture of the scanned
text into true text that can be processed further
in an application such as Word.
Output Devices
Output devices allow information to output
from a computer.
Examples of output devices are:

Monitors
 Printers

Projectors
 Plotters
Monitors
The monitor or visual display unit (VDU) is the
most significant output device.
Desktop displays use a cathode ray tube (CRT)
Laptops incorporate liquid crystal display (LCD)
Plasma
Monitors
Standard desktop monitors are Super VGA
Screen sizes vary from 14” to the larger
plasmas found on high end graphics
workstations
Resolution
Refers to the number of individual dots of color,
known as pixels, contained on a display.
Is expressed by the number of pixels on the
horizontal axis (rows) and on the vertical axis
(columns), such as 1024x768.
Monitors normally support resolutions matching the
physical pixel grid as well as the resolution
capability of your video card.
Dot Pitch
Is the measure of how much space there is
between a display’s pixels, the smaller the dot
pitch the better quality image displayed.
.22 mm
.25 mm
.26 mm
.28 mm
Refresh Rate
Refresh rate is the number of times that the screen
image is updated per second.
If your monitor has a refresh rate of 75 Hertz (Hz),
then it cycles through all the pixels from top to
bottom 75 times per second.
Too few cycles per second will cause flickering
which can lead to headaches and eye strain.
Color Depth
The combination of the display modes supported by
your monitor and graphics adapter determine how
many colors can be displayed.
Color capability is expressed as a BIT DEPTH.
The bit depth determines the number of colors that
can be displayed at one time.
Color Depth Chart
Bit-depth Number of colors
1
2
2
4
4
16
8
256
16
65,536
24
16,777,216
32
16,777,216
Monochrome
CGA
EGA
VGA
High color, XGA
True color, SVGA
True color + Alpha Channel
Printers
The types printer include:
 Laser – Expensive, used mostly in medium to large
organisations
 Ink Jet – Typically found in small business and
SOHO
 Dot Matrix – Found mostly in large organisations
for printing process reports and large volumes of
data
Printers
Speed – measured in Pages Per Minute
(PPM)
Quality – measured in Dots Per Inch (DPI)
The higher the DPI the better the print
quality