1. I/O Organization and Peripherals
Module V
I/O Organization and Peripherals

2. I/O Devices
Peripheral devices refer to any external device connected to the computer.
Computer peripherals can be divided into two categories:
Devices that perform input and output operations: Examples : Keyboard, Mouse, Printer, Video Display, etc
Devices for the secondary storage of data Examples : Magnetic disk, Floppy Disk, CD ROM, etc

3. Peripheral devices Peripheral devices to be studied in detail include:
Scanner
Plotter
Joysticks
Touchpad

4. UQ : Write short note on Scanners

5. Scanners
Scanners transform printed material and photographs into digital representations.
Most scanners use a flat-bed arrangement, in which the page being scanned is placed over a flat glass surface.
A source of light scans the page, and the reflected light is focused on a linear array of charge coupled devices (CCDs).
When a CCD device is exposed to light, an electrical charge is stored in a tiny capacitor associated with it such that the amount of charge is proportional to the intensity of light.
This charge is collected by appropriate circuitry and converted to a digital representation using an analog to digital converter.

6. Scanners
For color scanners, red green and blue filters are used to separate the primary colors and process them separately.
As the light source moves across the page, the sensor array is read repeatedly, thus sampling the successive lines of pixels of image.
After scanning the image is represented in memory as an array of pixels.

7. Scanners

8. UQ : Write short note on Plotters

9. Plotters
A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens.
The plotter can draw continuous point-to-point lines directly from vector graphics files or commands.
There are different types of plotters:
a drum plotter draws on paper wrapped around a drum which turns to produce one direction of the plot, while the pens move to provide the other direction;
a flatbed plotter draws on paper placed on a flat surface; and
an electrostatic plotter draws on negatively charged paper with positively charged toner.

10. Plotter

11. Plotters
Plotters were the first type of printer that could print with color and render graphics and full-size engineering drawings.
Plotters are much more expensive than printers.
They are most frequently used for
CAD (computer-aided design) and
CAM (computer-aided manufacturing).
Hewlett-Packard is the leading vendor of plotters worldwide

12. UQ : Write short note on Joysticks

13. Joysticks
Joystick is a short pivoted stick that can be moved by hand to point in any direction in the X-Y plane.
When this information is sent to the computer, the software moves the cursor on the screen in the same direction.
The position of the stick can be sensed by a suitable linear or angular position transducer, such as the potentiometer arrangement.
The voltage outputs of the X and Y potentiometers are fed to two analog-to-digital convertors , whose outputs determine the position of the joystick and thus the desired direction of motion

14. Joysticks

15. Joysticks Joysticks are widely used in video games.
For use in video games, the joystick is shaped into a handle that suits the nature of the game.
It is usually equipped with push buttons to be used for shooting a ball or firing a gun.

16. Joysticks

17. UQ : Write short note on Touchpad

18. Touchpad
The touchpad is a small pad made of pressure sensitive material.
When the user’s finger touches some point on the pad, the pressure causes the electrical characteristics of the material at that spot.
The location of the spot is detected and communicated to the computer.

19. Touchpad
By moving a finger across the pad, the user can instruct the software to move the cursor on the screen in the same direction.
This makes touchpad a low cost replacement for the mouse, with high degree of robustness and reliability because it contains no moving parts.

20. Touchpad
The most innovative material for implementing touchpad is the one that has a large number of optical fibers embedded in it.
The material can identify the location of an object touching it as well as the amount of pressure being applied.
This material was developed for robotic applications in space.
A touchpad can be combined with a liquid crystal display to produce a touch sensitive screen that can be used for both input and output operations.

21. Touchpad