input & output devices
DESCRIPTION
TRANSCRIPT
Input & Output Devices
V. Saranya
Input device
Enable to enter data and commands
1. Keyboard
• Keyboard primary input device
QWERTY layout
Additional spl keys
Input received operation
Keyboard Keyboardcontroller
Keyboard Buffer
System Software CPU
1. Press key2. A chip (k.C) notes that a key has been pressed3. K.C has K.B4. 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.
2. MOUSE
• Used to: select menu, access menu & interact with programmes.
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.
Optical Mouse
• Non mechanical mouse• Emits beam and lights
from underside• Use LED• Light reflection is used
to judge the distance, direction & speed.f
Usage • Clicking• Double clicking• Dragging• Right clicking
Benefits Cursor movement Selecting positionButton usage determined
by:• Os• Application Software• System Software
3. Trackball
4. Track pad
5. Touch Screens
• Optical touch screens– Use infra red (1 end)– Light detectors (2nd end)
• Electrical touch screens– 2 transparent plates– 1 conductive material– 2resistive material.
• Acoustic touch screens– High frequency sound
waves
6. Joystick
7. Light Pen
8. Data Glove
9. Digitizers
Used for tracing
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 scanner2. Sheet fed scanner3. Hand held scanner4. Drum scanner.
Output devices
• Hardcopy output• Softcopy output
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.
According to the colors
• Monochrome monitors:– Display only one color.
• Grayscale monitors– Display various shades of gray
• Color monitors.– Display different colors.
CRT monitor
2. Printers • Drum printers
Dot matrix printers
Ink Jet Printer
Laser Printer