4A.2.5.2 POINTING DEVICES

A pointing device is an input interface (specifically a human interface device) that allows a user to input spatial (i.e., continuous and multi-dimensional) data to a computer. While the most common pointing device by far is the mouse, many more devices have been developed.

A "rodent" is a technical term referring to a device which generates mouse-like input. However, the term "mouse" is commonly used as a metaphor for devices that move the cursor.

A mouse is a small handheld device pushed over a horizontal surface. A mouse moves the graphical pointer by being slid across a smooth surface. The conventional roller-ball mouse uses a ball to create this action: the ball is in contact with two small shafts that are set at right angles to each other. As the ball moves these shafts rotate, and the rotation is measured by sensors within

the mouse. The distance and direction information from the sensors is then transmitted to the computer, and the computer moves the graphical pointer on the screen by following the movements of the mouse. Another common mouse is the optical mouse. This device is very similar to the conventional mouse but uses visible or infrared light instead of a roller-ball to detect the changes in position. A Mini- mouse is a small egg-sized mouse for use with laptop computers; usually small enough for use on a free area of the laptop body itself, it is typically optical, includes a retractable cord and uses a USB port to save battery life. Three Devices similar to mouse are trackballs, touch pads and pointing sticks.

A trackball is a pointing device consisting of a ball housed in a socket containing sensors to detect rotation of the ball about two axes, similar to an upside-down mouse: as the user rolls the ball with a thumb, fingers, or palm the mouse cursor on the screen will also move.

A touchpad or trackpad is a flat surface that can detect finger contact. It's a stationary pointing device, commonly used on laptop computers. At least one physical button normally comes with the touchpad, but the user can also generate a mouse click by tapping on the pad. Advanced features include pressure sensitivity and special gestures such as scrolling by moving one's finger along an edge.

A pointing stick is a pressure sensitive small nub used like a joystick. It's usually found on laptops embedded between the 'G', 'H', and 'B' keys. It operates by sensing the force applied by the user. The corresponding "mouse" buttons are commonly placed just below the spacebar. It is also found on mice and some desktop keyboards.

A Joystick is the most popular input device for computer games.

A touch screen is a device embedded into the screen of the TV monitor, or system LCD monitor screens of laptop computers. Users interact with the device by physically pressing items shown on the screen, either with their fingers or some helping tool.

A light pen is a device similar to a touch screen, but uses a special light sensitive pen instead of the finger, which allows for more accurate screen input. As the tip of the light pen makes contact with the screen, it sends a signal back to the computer containing the coordinates of the pixels at that point.

Stylus is a pen like device commonly used with tablet PCs and PDAs. A stylus interacts with computer through handwriting

recognition software which translates handwritten notes into a form that the system unit can process

4A.2.5.3 SCANNER

Scanners move across text and images and convert them in a form that the system unit can process. A scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Some scanners can also read text by converting them to digital code. The scanners are very useful for convert in the typed pages into word-processing files. Graphic scanners convert a printed image into video image without converting it to digital code

There are three types of scanners: Optical Scanners,

Bar code readers and

Character and mark recognition devices.

Optical Scanner:

Optical Scanners, like traditional copy machines, can make a copy from an original. Simply known as scanner, accepts documents consisting of text and /or images and converts them into machine- readable form.

There are two types of optical scanners: Flatbed and Portable

Flatbed scanner is much like a copy machine. The image to be scanned is placed on a glass surface and the scanner records the image from below.

Portable scanner is typically a handheld device that slides across the image, making direct contact.

Card Readers:

Nearly everyone uses a credit card, debit card, access card or some type of identification card. These cards typically have the user‘s name, some type of identification number and signature embossed on the card. Card readers interpret this encoded information. By far the most common is magnetic card reader. The information is stored on a thin magnetic strip located on the back of the card. When the card is swiped through the magnetic card reader, the information is read.

Bar Code Readers:

Handheld wand readers or platform scanners containing photoelectric cells that scan or read bar codes or the vertical zebra striped marks printed on product containers.

Character and Mark Recognition Devices:

Character and Mark Recognition Devices are scanners that are able to recognize special characters and marks.

There are three types of Character and Mark Recognition Devices:

Magnetic Ink Character Recognition (MICR): It is used to recognize the magnetically charged characters. The Characters are written with special ink or magnetic ink. It is used in banks cheques and deposit slip

Optical Character Recognition (OCR): It is an Optical scanner used for reading bar code data. Printed characters consisting a number of bars of varying thickness & spacing between them can be read by light source and changed into machine readable code Bar code data. It is used for large volume applications like reading passenger ticket, computer printed bill of companies. It is used in department stores, issuing books in the library and encoding ID. Optical Mark Recognition (OMR): OMR is used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected & marked. The OMR detect the mark & sends corresponding signal to the processor. If the mark is present, the amount of reflected light is reduced & thus OMR detects the presence of the mark for each answer. Used for competitive exams having objective type questions.