Explain various input devices of computer ?

Input Devices

An input device is used to feed data and instructions into the computer,

Keyboard

The keyboard is the main input device for computers. Computer keyboards loo very similar to the keyboards of typewriters, with some addition keys, most keyboards have between 80- and 110 keys, which include the following : Typing keys : These include the letters of the alphabet. The QWERTY patterns has been a standard right from the time computer keyboards were introduced. Numeric keys : These include a set of 17 keys, arranged in the same configuration found on   calculators to speed up data entry of numbers. Function keys : These are used by applications and operating systems to input specific commands. Control keys : These are used handle control of the cursor and the screen. Advantage The keyboard is easy to use and cheap. Disadvantages ·         The keyboard cannot be used to draw figures. ·         The process of moving the cursor to another position is very slow.

Pointing Devices

A pointing input device enables the users to easily control the movement of the pointer to select items on a display screen, to select commands from commands menu, to draw graphs, etc., Mouse It is the key input device used in a graphical user interface (GUI). It can be used to handle the pointer easily on the screen to perform various functions such as opening a program of file. The mouse has two buttons and a scroll wheel. It can be held in the hand and easily moved. Point Placing the mouse pointer over the word or the object on the screen. Click Pressing either the left or the right button of the mouse is known as clicking. Clicking a mouse button initiates some action. Drag Dragging means pointing to a desired location while pressing the left button. Scroll The scroll wheel, which is placed in between the left and right buttons of the mouse, is used to vertically scroll through long documents. Mechanical mouse This type of mouse has a rubber or metal ball at its bottom and an electronic circuit containing sensors. When the mouse is moved over a flat surface, the sensors detect the direction of movement of the ball. The electronic circuit translates the movement into signals and feeds it as input to the computer. Optical mouse The optical mouse is more advanced than the mechanical mouse. It contains a ball inside. The movement of the mouse is detected using laser technology, by using optical sensors. Cordless mouse A cordless or wireless mouse is not connected to the computer. The movement of the mouse is detected using radio waves or infrared light waves. Advantages ·    The mouse is easy to use and can be used to quickly place the cursor anywhere on the screen. ·     It also helps to quickly and easily drawn figures. ·     It is cheap. ·     Its point-and-click capabilities make it unnecessary to remember and type in commands. Disadvantages ·     The mouse needs extra desk space to be placed and moved easily. ·     The ball in the mechanical mouse must be cleaned to removed dust from it. Trackball A trackball is a pointing device that is used to control the position of the cursor on the screen. It is usually used in notebook computers, where it is placed on the keyboard. The user rolls the ball to position the cursor at an appropriate position on the screen and then clicks one of the buttons (identical to mouse buttons) near the trackball, either to select objects or to position the cursor for text entry. Advantages ·         The trackball provides better resolutions. ·         It occupies less space. ·         It is easier to use as compared to a mouse. Disadvantage The trackball chamber is often covered with dust, so it must be cleaned regularly. Touchpad A touchpad is a small, flat, rectangular stationary pointing device with a sensitive surface of 1.5–2 square inches. The user has to slide his or her fingertips across the surface of the pad to point to a specific object on the screen. There are also buttons around the edge of the pad that work like mouse buttons. Touchpads are widely used in laptops, and are in built on the laptops keyboards. Advantages ·         Touchpads occupy less space. ·         They are easier to use as compare to a mouse.

Handheld Devices

Joystick A joystick is a cursor control device widely used in computers games and computer aided design (CAD) / computer aided manufacturing (CAM) applications. A joystick has one or more push buttons, called switches, whose position can also be read by the computer. The lever of a joystick moves in all directions to control the movement of the pointer on the computer screen. Stylus A stylus is a pen-shaped input device used to enter information or write on the touchscreen of a handheld device. It is a small stick that can also be used to draw lines on a surface as input into a device, choose an option from a menu, move the cursor to another location on the screen, take notes, and create short messages. Touchscreen A touchscreen is a display screen that can identify the occurrence and position of a touch inside the display region. The user can touch the screen either by using a finger or a stylus.

Optical Devices

Optical devices, also known as data-scanning devices, use light as a source of input for detecting or recognizing different objects such as characters, marks, codes, and images. The optical device converts these objects into digital data and sends it to the computer for further processing. Barcode Reader A barcode reader is a handheld input device that is used to capture and read information stored in a bar code. It consists of a scanner, a decoder, and a cable used to connect the reader to a computer. The function of the barcode reader is to capture and translate the bar code into numerical and / or alphabets. It is connected to a computer for further processing of the captured information. Advantage ·         Barcodes readers are cheap. ·         They are portable. ·         They are handy and easy to use. Disadvantages ·     Barcode readers must be handled with care. If they develop a scratch, the user may not be able to read the code. ·    They can interpret information using a limited series of thin and wide bars. To interpret other unique identifiers, the bar display area must be widened. Image Scanner A scanner is a device that captures images, printed text, and handwriting, from different sources such as photographic prints, posters, and magazines and converts them into digital image for editing and display on computers. Advantages ·    Any printed or handwritten document can be scanned and stored in a computer for further processing. ·  The scanned and stored document will never deteriorate in quality with time. The document can be displayed and printed whenever required. ·    There is no fear of loss of documents. The user can scene important documents and store them permanently in the computer. Disadvantage ·      Scanners use usually costlier than other input devices. ·      The documents that are scanned and stored as images have a higher size as compared to other equivalent text files. ·     Text documents are scanned and stored as images. Therefore, they occupy more space and are also uneditable because computers cannot interpret individual characters and numbers in the image. Optical Character Recognition Optical character recognition (OCR) is the process of converting printed materials into text or word processing files that can be easily edited and stored. The steps involved in OCR include : ·    Scanning the text character by character. ·     Analyzing the scanned image to translate the character images into character codes. Advantages ·     Printed documents can be converted into text files. ·     Advanced OCR can recognize handwritten text and convert it into computer-readable text files. Disadvantages ·         OCR cannot recognize all types of fonts. ·         Documents that are poorly or have strike over cannot be recognized. ·      Very old documents when passed through OCR may not convert into an exact copy of  the text file. Optical Mark Recognition Optical mark recognition (OMR) is the process of electronically extracting data from marked fields, such as check boxes and fill-in fields, on printed forms. The OMR sheet is scanned by the reader to detect the presence of a mark by measuring the reflected light levels. Advantage Optical mark readers work at very high speeds. They can read up to 9,000 forms per hour. Disadvantages ·         It is difficult to gather large amounts of information using an OMR. ·         Some data may be missing in the scanned document. ·         It is a sensitive device that rejects the OMR sheet if it folded, torn, or crushed. Magnetic Ink Character Reader Magnetic ink character reader (MICR) is used to verify the legitimacy of paper documents, especially bank checks. It consists of magnetic ink printed characters that can be recognized by high-speed magnetic recognition devices.  MICR is widely used to enhance security, speed up the sorting of documents, and minimize the exposure to cheque fraud.

Audio–visual Input Devices.

Today, all computers are multimedia-enabled, that is, computers not only allow one to read or write text. But also enable the user to record songs, view animated moves, etc. Audio Input Devices Audio devices are used to either capture or create sound. They enable computers to accept music, speech, or sound effects for recording and / or editing. Microphones and CD players are examples of two widely used audio input devices. The sound card is a hardware unit that converts analogue signals generated through the microphone into digital data, so that it can be stored in the computer. When the user wants to hear the pre-recorder audio input, the sound card converts the digital data into equivalent analogue signals and sends them to the speakers. A computer with a microphone and speakers can be used to make telephone calls and do videoconferencing (using a web camera or ‘webcam’) over the internet. Video Input Devices video input devices are used to capture video from the outside world into the computer. Here, the term video means moving picture along with sound (as in television). As we have sound cards to convert analogue audio signals into digital data and vice versa, we also have video cards to convert analogue video signals to digital data to store it in the computer (and vice versa). Digit camera and web camera are popular examples of video input devices. Advantages ·         Audio devices can be used by people who have visual problems. ·    Audio input devices are best used in situation where users want to avoid input through keyboard or mouse. ·         Video input devices are very useful for applications such as videoconferencing. ·         They can be used to record memorable moments in one’s life. ·         They can also be used for security purposes. Disadvantages ·       Audio input devices are not effective in noisy places. ·     With audio input devices, it is difficult to clearly distinguish between two similar sounding words. ·      Videos and images captured using video input devices have very big file sizes, and they must be compressed before being stored on the computer.