Input Devices

Contents Introduction Common Input Devices

KEYBOARD WORKING OF KEYBOARD

MOUSE WORKING OF MOUSE

JOYSTICK TRACK BALL SCANNER

WORKING OF A SCANNER TYPES OF SCANNER

MAGNETIC INK CARD READER (MICR): OPTICAL CHARACTER RECOGNITION(OCR): OPTICAL MARK READER (OMR)

Introduction In computing, an input device is any peripheral (piece

of computer hardware equipment) used to provide data and control signals to an information processing system such as a computer or other information appliance.

Input devices are components or peripheral devices that feeds data or instructions into a computer or other computational devices for display, storage, processing, or outputting or transmission. They convert the instructions and analog data like graphics, sound, pictures into digital signals that can be processed by a computer. Examples of input devices are mouse, bar-code reader, magnetic-stripe reader, keyboard, modem, scanner, graphic tablet and stylus.

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Keyboard Mouse Joy stick Track Ball Scanner Magnetic Ink Card Reader(MICR) Optical Character Reader(OCR) Optical Mark Reader

Common Input Devices

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Key points regarding keyboard: The keyboard is the standard input device. It is merely collection of keys. It allows us to communicate with computer. It is similar to typewriter. Typewriter record data on paper but in keyboard data is stored in memory. A standard keyboard has 101/102 keys and also known as QWERTY keyboard.

Keyboard

SR. NO.

KEYS DISCRIPTION

1. TYPING KEYS

These keys include the letter keys (A-Z) and digits keys (0-9) which aregenerally give same layout as that of typewriters.

2. NUMERIC KEYS

I t is used to enter numeric data or cursor movement. Generally, it consistsof a set of 17 keys that are laid out in the same configuration used by mostadding machine and calculators.

3. FUNCTION KEYS

The twelve functions keys are present on the keyboard. These are arrangedin a row along the top of the keyboard. Each function key has uniquemeaning and is used for some specific purpose.

4. CONTROL KEYS

These keys provides cursor and screen control. I t includes four directionalarrow key. Control keys also include Home, End, Insert, Delet ,page up, page down Control(Ctrl), Alternate(Alt), Escape(Esc).

5. SPECIAL PURPOSE KEYS

Keyboard also contains some special purpose keys such as Enter, Shift,Caps Lock, Num Lock, Space bar, Tab, and Print Screen.

When any key is pressed in keyboard, the spring blow presses down thus completing the circuit. The tiny chip KEYBORDS CONTROLLER notes which key is being pressed. It sends interrupt request to the O.S. It also sends a code called scan code to the KEYBOARD BUFFER the system software respond to the interrupt by reading scan code this scan code is combination of bit patterns is then passed to CPU .the ASCII code using appropriate software's in the computer for that bit pattern which is transmitted to an external device for I/O processor.

WORKING OF KEYBOARD

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Stanford research center invented the first mouse on 1965. It rolls on a small ball and has two or three buttons on the top. The cursor moves very fast with mouse giving you more freedom to work in any direction. It is easier and faster to move through a mouse. It s user-friendly for computer beginners. A mouse is easy and convenient to use with a graphical user interface.

MOUSE

There is a small ball underneath a mouse , the ball moves too. As the ball moves it rubs against two rollers. One roller senses the horizontal movement and other vertical. These rollers together can tell in which direction the user moves the mouse. Each roller is attached to a wheel called ENCODER. This encoder turns with the rollers. As the encoder turns, its metal bridges touches two fixed electrical contact which generates electrical pulses. The movement of mouse tells with which rate the electrical pulse is generated. These signals are send to the computer through mouse cables. These signals are read by software called the MOUSE DRIVER. This software tells your computer how to move mouse pointer so that it matches mouse movement.

WORKING OF MOUSE

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Joystick was discovered by Robert Esnalt-Pelterie on 1st jan. 1909. Robert Esnalt-Pelterie came up with the idea of the joystick in his diary. It works on the principle of trackball. The first joystick was used to fly a plane,. Today they are commonly used in video games.

Joystick

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Track ball is an input device that is mostly used in notebook or laptop computer. A trackball is good for limited desk space because the user does not have to move the entire device. A trackball is usually not as accurate as a mouse. The ball mechanism of trackballs also requires more frequent cleaning than a mouse.

Track Ball

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Roudolph Hell invented a scanner on 1st Jan. 1963. The purpose of this object is to scan documents, pictures etc. Electronic format of scanned image is its bit map representation. Stored image can be altered or manipulated with an image processing software.

Scanner

Scanners operate by shining light at the object or document being digitized and directing the reflected light (usually through a series of mirrors and lenses) onto a photosensitive element. In most scanners, the sensing medium is an electronic, light-sensing integrated circuit known as a charged coupled device (CCD). Light-sensitive photosets arrayed along the CCD convert levels of brightness into electronic signals that are then processed into a digital image.

Two other technologies, CIS (Contact Image Sensor), and PMT (photomultiplier tube) are found in the low and high ends of the scanner market, respectively. CIS is a newer technology that allows scanners to be smaller and lighter, but sacrifices dynamic range, depth-of-field, and resolution. PMT-based drum scanners produce very high-quality images, but have limited application in library .Another sensing technology, CMOS (Complementary Metal Oxide Semiconductor), appears primarily in low-end, hand-held digital cameras where its low cost, low power consumption and easier component integration permits smaller, less expensive designs.

Working of a Scanner

Flat Bed Scanner Hand Held Scanner

Flat Bed Scanner: Looks like a photocopy machine. Has a box with a glass plate on the top & a lid. Document to be scanned is placed on the glass plate. A light source below the glass plate moves from one line to another and scans all these files. Take few seconds to scan a document.

Types of Scanner

Hand Held Scanner: Contains LED and can be held on hand. To scan dragged slowly over the document from one end to another. It has to be dragged very slowly and steadily. Used only when light accuracy is not needed. It is cheaper than the flat bed scanner. Used when the volume of the document to be scanned is low.

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MICR is used by banking industry for faster processing of large volume of cheques Bank’s identification code (name, branch etc.), account number and cheque number are pre-printed (encoded)using characters from a special character set on all cheques Special ink is used that contains magnetizable particles of iron oxide MICR reader-sorter reads data on cheques and sorts them for distribution to other banks or for further processing.

MAGNETIC INK CARD READER (MICR):

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‘Its the mechanical or electronic conversion of scanned images of handwritten, typewritten or printed text into machine-encoded text’.

OPTICAL CHARACTER RECOGNITION(OCR):

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‘Optical mark recognition (also called optical mark reading and OMR) is the process of capturing human-marked data from document forms such as surveys and tests’.

OPTICAL MARK READER (OMR)

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