In this part II of the article on input devices we will discuss about the following input devices --
light pens, touch screens, scanners and bar code readers. Unlike the keyboards and mice, these
devices are used for special purpose applications.


Light pen

A light pen is a small pen shaped input device which is used to write on a special electronic writing
pad. The Light pen is used for inputing small amounts of text into the computer. If you want to store
your signature inside the computer you can make use of the light pen. However, the signatures are
stored as graphics and not as text. It is easy to store the signatures by means of the light pen, but
recognizing that writing would be a much more difficult task. In the future, as the technology improves
the Light pens will be extensively used for handwriting recognition.


Touch Screen

Touch screens are input devices that allow you to select options on the computer screen just by
touching the screen at various positions. There are two technologies for touch screen -- one that
utilizes sensors that can detect the touch, the other utilizing the pressure detected on a pressure
pad placed just below the screen.

Touch screens are used in advertising kiosks, public information booths or in ATM machines. They are
used in drug stores, supermarkets etc. Where it is not advisable to use the keyboard or the mouse.
Touch screens are also used in public places where the environment is too dusty for the use of the
keyboard or the mouse.


Scanner

Scanners are input devices that scan the documents, images and photos and convert them into
electronic form to be stored into the computer. Scanners work on the same principle as that of the
Photocopying machines and the fax machines. The images are scanned by a moving light source and
the reflected light is collected by a group of light sensors, which is then converted into the electronic
image. This image is stored onto the hard disk.

Originally, scanners were of the hand held type and the documents, images or photos had to be
scanned manually. The images obtained by the hand held scanner were not satisfactory because
of the problems caused by the irregular movements of the hand. The latest type of scanner is the flat
bed scanner. It utilizes automatic scanning method, where a source of light scans the documents,
images or photos. automatically. As the scanning is uniform the scanned image is  better and there
is no distortion. Flat bed scanners are the most popular type of scanners in use today.


Bar code reader

Bar Code readers are hand held input devices which are used for reading the bar-code labels. The
bar-code labels are stuck on the products and contain information as to the name, type and price of
the products. When the bar code reader is scrolled across the bar-code it scans the code and the
software  inside the computer converts the code into the information about the product.

Bar code readers are of many different types and you can select the one that is suitable for your
application. The main type of bar-code readers are the pen type, laser type, CCD type and the camera
based bar-code readers. The camera based bar-code readers are the latest type and these readers
can the take image of the bar code and store it in your computer.The image is than converted into
data about the product.

The bar code readers use the serial port or the usb port for connecting to the computer. Wireless
bar-code readers have also been developed.

The bar-code readers are used in stores, malls, factories etc for inventory control and assets control
applications.