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