1. Input & Output Devices
V. Saranya

2. Input device
Enable to enter data and commands

3. QWERTY
layout 1. Keyboard
• Keyboard primary input device
Additional spl
keys

4. Input received operation
Keyboard Keyboard System
Keyboard CPU
controller Buffer Software
1. Press key
2. A chip (k.C) notes that a key has been pressed
3. K.C has K.B
4. K.C places a code of pressed key in this buffer.
5. K.C indicates S.S that something has happened by sending a signal to it.
6. S.S determine appropriate response.
7. The system reads the code of the pressed key from the keyboard buffer
and sends that code to the CPU.

5. 2. MOUSE
• Used to: select menu, access menu & interact
with programmes.

6. Mechanical Mouse
• Moving the mouse
turns the ball
• X and Y rollers grip the
ball & transfer
movement.
• Inside sensors send
signals to the computer
which tell it the
distance, direction &
Speed of the ball’s
motions.

7. Optical Mouse
• Non mechanical mouse
• Emits beam and lights
from underside
• Use LED
• Light reflection is used
to judge the distance,
direction & speed.f

8. Usage Benefits
• Clicking  Cursor movement
• Double clicking  Selecting position
• Dragging Button usage determined
• Right clicking by:
• Os
• Application Software
• System Software

9. 3. Trackball

10. 4. Track pad

11. 5. Touch Screens
• Optical touch screens
– Use infra red (1 end)
– Light detectors (2nd end)
• Electrical touch screens
– 2 transparent plates
– 1 conductive material
– 2resistive material.
• Acoustic touch screens
– High frequency sound
waves

12. 6. Joystick

13. 7. Light Pen

14. 8. Data Glove

15. 9. Digitizers
Used for tracing

16. 10. Scanners
1. doc/photograph is mounted on
a rotating drum.
2. Light beam is directed at the
pic and the amount of light
reflected is measured by
photocell.
3. Drum rotates, the light source
moves from one end to the
other.
Types:
1. Flatbed scanner
2. Sheet fed scanner
3. Hand held scanner
4. Drum scanner.

17. Output devices
• Hardcopy output
• Softcopy output

18. 1. Monitor
• Computer sends processed data to the
monitor when the user needs to observe the
output.
– CRT monitor (Cathode ray tube)
– Flat panel display.

19. According to the colors
• Monochrome monitors:
– Display only one color.
• Grayscale monitors
– Display various shades of gray
• Color monitors.
– Display different colors.

20. CRT monitor

21. 2. Printers
• Drum printers

22. Dot matrix printers

23. Ink Jet Printer

24. Laser Printer