Types of input devices of the computer system

In the previous session we studied about the types of devices used in computer systems. Out of which in this blog we are going to study in detail about the types of input devices.A computer accepts input in two ways, either manually or directly. In case of manual data entry, the user enters the data into computer by hand, for example, by using keyboard and mouse. A user can also enter data directly by transferring information automatically from a source document (like from cheque using MICR) into the computer. The user does not need to enter information manually. Direct data entry is accomplished by using special direct data entry devices like a barcode reader. Some of the commonly used input devices are keyboard, pointing devices like mouse and joystick, digital camera, and scanners.Here we will learn about all this type of input devices in details.

• A keyboard is the most common data entry device. Using a keyboard, the user can type text and commands. Keyboard is designed to resemble a regular typewriter with a few additional keys. Data is entered into computer by simply pressing keys. The layout of the keyboard has changed very little ever since it was introduced. In fact, the most common change in its technology has simply been the natural evolution of adding more keys that provide additional functionality. The number of keys on a typical keyboard varies from 84 keys to 104 keys.
• Portable computers such as laptops quite often have custom keyboards that have slightly different key arrangements than a standard keyboard. In addition, many system manufacturers add special buttons to the standard layout. Keyboard is the easiest input device, as it does not require any special skill. Usually, it is supplied with a computer and so no additional cost is incurred.
• The maintenance and operational cost of keyboard is also less. However,using a keyboard for data entry may be a slow process because the user has to manually type all the text. In addition, it can be difficult for people suffering from muscular disorder.

• Most computers come with an alphanumeric keyboard but in some applications,keyboard is not convenient.For example,if the user wants to select an item from a list, the user can identify and position those items by selecting them through the keyboard.However,this action could be performed quickly by pointing at the correct position.A pointing device is used to communicate with the computer by pointing to locations on the monitor screen.
• Such devices do not require keying of characters, instead the user can move a cursor on the screen and perform move, click or drag operations.Some of the commonly used pointing devices are mouse, trackball, joystick, light pen, and touch screen.

Mouse

• Mouse is a small hand-held pointing device with a rubber ball embedded at its lower side and buttons on the top. Usually, a mouse contains two or three buttons, which can be used to input commands or information. It may be classified as a mechanical mouse or an optical mouse, based on the technology it uses. A mechanical mouse uses a rubber ball at the bottom surface, which rotates as the mouse is moved along a flat surface, to move the cursor. It is the most common and least expensive pointing device. An optical mouse uses a light beam instead of a rotating ball to detect movement across a specially patterned mouse pad. As the user rolls the mouse on a flat surface, the cursor on the screen also moves in the direction of the mouse’s movement. It is pricier than their mechanical counterparts but are accurate and often do not need a mouse pad.

• With the increasing use of wireless technology, the wireless versions of keyboard and mouse have also been developed. Rather than connecting through wires, they connect with computer using one of the three technologies,namely, Bluetooth, infra-red, or radio frequency. The wireless keyboard requires three AA batteries and the wireless mouse requires two AA lithium batteries to operate. They also have a power switch on the bottom to turn them ON or OFF. The use of wireless devices
  helps in eliminating the wiring tangles around the PC and provides mobility and flexibility to the user to position him/her self-relative to the computer.

Pointing Devices

• Most computers come with an alphanumeric keyboard but in some applications, keyboard is not convenient. For example, if the user wants to select an item from a list, the user can identify and position those items by selecting them through the keyboard. However, this action could be performed quickly by pointing at the correct position. A pointing device is used to communicate with the computer by pointing to locations on the monitor screen.
• Such devices do not require keying of characters, instead the user can move a cursor on the screen and perform move, click or drag operations.Some of the commonly used pointing devices are mouse, trackball, joystick, light pen, and touch screen.

Trackball

• Trackball is another pointing device that resembles a ball nestled in a square cradle and serves as an alternative to a mouse. In general, a trackball is as if a mouse is turned upside down. It has a ball, which when rotated by fingers in any direction, moves the cursor accordingly. The size of the ball in the trackball varies from as large as a cue ball, to as small as a marble. Since it is a static device, instead of rolling the mouse on the top of the table the ball on the top is moved by using fingers, thumbs, and palms.This pointing device comes in various shapes and forms but with the same functions. The three shapes, which are commonly used,are a ball, button, and square.

• A joystick is a device that moves in all directions and controls the movement of the cursor. The basic design of a joystick consists of a stick that is attached to a plastic base with a flexible rubber sheath. This plastic base houses a circuit board that sits beneath the stick.The electronic circuitry measures the movement of the stick from its central position and sends the information for processing.

• A joystick also consists of buttons that can be programmed to indicate certain actions once a
  position on the screen has been selected using stick. It offers three types of control: digital, glide, and direct.Digital control allows movement in a limited number of directions such as up, down, left, and right. Glide and direct control allow movements in all directions (360 degrees).Direct control joysticks have the added ability to respond to the distance and speed with which the user moves the stick.
• A joystick is generally used to control the velocity of the screen cursor movement rather than its absolute position.It is used for computer games.The other applications in which it is used are flight simulators, training simulators, CAD/CAM systems, and for controlling industrial robots.

Light Pen

• There are a number of situations when some information (picture or text) is available on paper and is needed on the computer for further manipulation. A scanner is an input device that converts a document into an electronic format that can be stored on the disk.The electronic image can be edited, manipulated, combined, and printed by using the image editing software. The scanners are also called optical scanners as they use a light beam to scan the input data.
• Note that most of the scanners come with a utility program that allows it to communicate with the computer and save the scanned image as a graphic file on the computer. Moreover, they can store images in both gray-scale and color mode. The two most common types of scanners are hand-held and flat-bed scanner.

• A hand-held scanner consists of light emitting diodes, which are placed over the document to be scanned. This scanner performs the scanning of the document very slowly from the top to the bottom with its light on.In this process, all the documents are converted and then stored as an image. While working, the scanner is dragged very steadily and carefully over the document at a constant speed without stopping, or jerking in order to obtain best results.
• Hand-held scanners are widely used where high accuracy is not of much importance.The size of the hand-held scanners is small. They come in various resolutions, up to about 800 dpi (dots per inch) and are available in either grey scale or colour.
• Furthermore, they are used when the volume of the documents to be scanned is low. These devices read the data on the price tags, shipping labels, inventory part number, book ISBNs, and so on.

2.Flat-bed Scanner

• Flat-bed scanners look similar to a photocopier machine. It consists of a box containing a glass plate on its top and a lid that covers the glass plate. This glass plate is used for placing the document to be scanned.The light beam is placed below the glass plate and when it is activated, it moves horizontally from left to right.
• After scanning one line, the light beam moves in order to scan the next line and the procedure is repeated until all the lines are scanned. For scanning, an A4 size document takes about 20 seconds. These scanners can scan black and white as well as colour images.
• The flatbed scanners are larger in size and more expensive than the hand-held scanners. However, they usually produce better quality images because they employ better scanning technology.

Optical Character Recognition (OCR)

• As stated earlier, a scanner converts an input document into an electronic format that can be stored on the disk. If the document to be scanned contains an image, it can be manipulated using image editing software. However, if the document to be scanned contains text, you need optical character recognition (OCR) software. This is because when the scanner scans a document, the scanned document is stored as a bitmap in the computer’s memory. The OCR software translates the bitmap image of text to the ASCII codes that the computer can interpret as letters, numbers, and special characters.
• Because of OCR, data entry becomes easier, error-free and less time consuming. However, it is very expensive and if the document is not typed properly, it will become difficult for the OCR to recognize the characters. Furthermore, except for tab stops and paragraph marks, most document formatting is lost during text scanning. The output from a finished text scan will be a single column editable text file. This text file will always require spell checking and proof reading as well as re-formatting to get the desired
  final layout.

Optical Mark Recognition (OMR)

• Optical mark recognition is the process of detecting the presence of intended marked responses. A mark registers significantly less light than the surrounding paper. Optical mark reading is done by a special device known as optical mark reader. In order to be detected by the OMR reader, a mark has to be positioned correctly on the paper and should be significantly darker than the surrounding paper.
• The OMR technology enables a high speed reading of large quantities of data and transferring this data to computer without using a keyboard. Generally, this technology is used to read answer sheets (objective type tests). In this method, special printed forms/documents are printed with boxes, which can be marked with dark pencil or ink. These forms are then passed under a light source and the presence of dark ink is transformed into electric pulses, which are transmitted to the computer.
• OMR has a better recognition rate than OCR because fewer mistakes are made by machines to read marks than in reading handwritten characters. Large volumes of data can be collected quickly and easily without the need for specially trained staff. Usually, an OMR reader can maintain a throughput of 1500 to 10000 forms per hour.
• However, the designing of documents for optical mark recognition is complicated and the OMR reader needs to be reprogrammed for each new document design. OMR readers are relatively slow because the person putting marks on the documents must follow the instructions precisely. Any folding or dirt on a form may prevent the form from being read correctly. In addition, it requires accurate alignment of printing on forms and needs a paper of good quality.

Magnetic Ink Character Reader (MICR)

• You must have seen special magnetic encoding using characters, printed on the bottom of a cheque. The characters are printed using special ink, which contains iron particles that can be magnetized. To recognize these magnetic ink characters, a magnetic ink character reader (MICR) is used. It reads the characters by examining their shapes in a matrix form and the information is then passed on to the computer.

• Bar code is a machine-readable code in the form of a pattern of parallel vertical lines of varying widths.It is commonly used for labelling goods that are available in super markets and numbering books in libraries. This code is sensed and read by a bar code reader using reflective light.
• The information recorded in bar code reader is then fed into the computer, which recognises the information from the thickness and spacing of bars. Bar code readers are either hand-held or fixed-mount. Hand-held scanners are used to read bar codes on stationary items.
• With fixed-mount scanners,items having a bar code are passed by the scanner by hand as in retail scanning applications or by conveyor belt in many industrial applications.
• Bar code data correction systems provide enormous benefits for just about every business with a bar code data-collection solution, capturing data is faster and more accurate. A bar code scanner can record data five to seven times faster than a skilled typist. A bar code data entry has an error rate of about 1 in 3 million. Bar coding also reduces cost in terms of labour and revenue losses resulting from data collection errors. Bar code readers are widely used in supermarkets,department stores, libraries, and other places.
• You must have seen bar codes on the back cover of certain books and greeting cards. Retail
  and grocery stores use a bar code reader to determine the item being sold and to retrieve the
  item price from a computer system.
• Bar code scanners are electro-optical systems that include a means of illuminating the symbol and measuring reflected light. The light waveform data is converted from analog to digital, in order to be processed by a decoder, and then transmitted to the computer software. The process begins when a device directs a light beam over a bar code.
• The device contains a small sensory reading element, called sensor,which detects the light being reflected back from the bar code, and converts light energy into electrical energy.
• The result is an electrical signal that can be converted into an alphanumeric data.The pen in the bar code unit reads the information stored in the bar code and converts it into a series of ASCII characters by which the operating system gets the information stored in the bar code.

Conclusion