1. Introduction of Computer
1.3 Components of Computer System?
1.3.3 Other Input Unit
These are scanner devices that are capable of detecting alphabetic and numeric characters by comparing the shapes with internally stored patterns. These are expensive and are used only for large-volume processing applications e.g. by credit-card companies
These scanners are capable of recognising a pre-specified type of mark made by a pencil. These are normally used for validation of input documents, evaluating answer-sheets in objective-type tests e.g. GRE, GMAT.
3. Bar Code Reader
Data coded in the form of light and dark lines or bars are known as bar codes. Bar codes are used particularly by the retail trade for labeling goods. Bar code reader is a device used for reading bar code data which is performed by laser beam scanner which is linked to a computer.
4. Desk Scanning
The scanning process involves application of the light source to the image. The light is reflected back form the image into the scanner optics where the varying levels of light are interpreted.The image is then reconstructed digitally and displayed on the screen.
5. Touch Screen
It is a computer screen designed or modified to recognize the location of a touch on its surface. By touching the screen, the user can make a selection or move a cursor. The simplest type of touch screen is made up of a grid of sensing lines, which determine the location of a touch by matching vertical and horizontal contacts.
6. Light Pen
A light pen is a pointing device. It is used to select a displayed menu option on the CRT. It is a photosensitive pen like device. It is capable of sensing a position on the CRT screen when its tip touches the screen. When its tip is moved over the screen surface, its photocell sensing element detects the light coming from the screen and the corresponding signals are sent to the processor.