THE FOLLOWING IS A LIST OF THE MOST COMMON INPUT DEVICES WHICH ARE NOWADAYS FOUND IN A COMPUTER SYSTEM: 1 ST KEYBOARD 2 ND MOUSE 3 RD JOY STICK 4 TH LIGHT PEN 5 TH TRACK BALL 6 TH SCANNER 7 TH GRAPHIC TABLET(DIGITIZER) 8 TH MICROPHONE 9 TH MAGNETIC INK CARD READER(MICR) 10 TH OPTICAL CHARACTER READER(OCR) 11 TH BAR CODE READER 12 TH OPTICAL MARK READER input devices...... Input is any data or instructions entered into the memory of a computer. input device is any hardware component that allows a user to enter data and instructions into a computer.
Transcript
THE FOLLOWING IS A LIST OF THE MOST COMMON INPUT DEVICES WHICH ARE NOWADAYS FOUND IN A COMPUTER SYSTEM:
1ST KEYBOARD2ND MOUSE3RD JOY STICK4TH LIGHT PEN5TH TRACK BALL6TH SCANNER7TH GRAPHIC TABLET(DIGITIZER)8TH MICROPHONE9TH MAGNETIC INK CARD READER(MICR)10TH OPTICAL CHARACTER READER(OCR)11TH BAR CODE READER12TH OPTICAL MARK READER
input devices......Input is any data or instructions entered into the memory of a computer.input device is any hardware component that allows a user to enter data and instructions into a computer.
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.
Different categories of keys in 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.
Working of keyboard:
WORKING OF KEYBOARD.......
KEYBOARDCONTROLLER
KEYBOARD BUFFER
SYSTEM SOFTWARE
CPU
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.
2nd MOUSE:MOUSE IS A HAND HEALD DIVICE THAT ALLOWS USER TO MOVE ITEMS ON THE SCREEN.
KEY POINTS REGARDING MOUSE:
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.
WORKING OF 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.
Action performed by mouse.
• Double clicking• Dragging • Right clicking • Scrolling
3rd Joystick:‘Joystick is also a pointing device which is used to
move cursor position on a monitor screen. ’Key points of joystick :
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.
4th LIGHT PEN:‘they are pen shaped devices are used to select the screen icons by detecting the light coming from the CRT screen.’Key features of light pen:
It was used as a mouse on old computers.
This device was created by DESIGN STAFF on 27th may 1982.
I t consists of a photocell and an optical system placed in a small tube.
Light pens are used by health care professionals
(such as doctors and dentists) and design work.
Using a light pen is more direct and precise than using a mouse.
Light pen is also convenient for applications with limited desktop space
Light pens normally require a specially designed monitor to work with
Working:
‘When light pen' s tip is moved over the monitor screen and pen button is pressed, its photocell sensing element detects
the screen location and sends the corresponding signal to the CPU.’
5th TRACK BALL:A trackball is a stationary pointing device with a ball mechanism on its top.
KEY POINTS OF TRACK BALL:
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.
6th SCANNER:‘A scanner is a light-sensing input device that converts printed text and graphics into a digital form that can be further processed by the computer ’Key points of scanner:
Roudolph Hell invented a scanner on 1st Jan. 1963.
The purpose of this object is to scan documents, pictures, and etc.
Electronic format of scanned image is its bit map representation.
Stored image can be altered or manipulated with an image processing software.
TYPES OF SCANNER:1.flat bed scaner,2.hand held scanner
1st 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.
2nd 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 the the flat bed scanner.
Used when the volume of the document to be scanned is low.
Working of a 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 photosites 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.
GRAPHIC TABLET (DIGITIZER):‘A graphics tablet or digitizer is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper’.
Key points of a digitizer:
The first electronic handwriting tablet was the Telautograph, patented by Elisha Gray in 1888.
The device consists of a flat surface upon which the user may "draw" or trace an image using an attached stylus.
The image generally does not appear on the tablet itself but, rather, is displayed on the computer monitor.
It provides a very natural way to create a computer graphic.
Commonly used in the area of computer aided design (CAD) by architects and engineer for virtual designing.
MICROPHONE:‘a microphone is an input device that convert sound into electrical signals’.
Key points of microphone:
Emile Berniler invented the first microphone at the US Cenntinnial Exposition on 26 july 1876.
Microphones are a type of transducer - a device which converts energy from one form to another.
This input device was used for 1 or more to communicate with a crowd or to communicate through a webcam.
the diaphragm vibrates, it causes other components in the microphone to vibrate. These vibrations are converted into an electrical current which becomes the audio signal.
MAGNETIC INK CARD READER (MICR):‘Magnetic ink character recognition (MICR) is a character-recognition technology used mainly by the banking industry to ease the processing and clearance of cheques and other documents’. Key points of MICR:
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.
OPTICAL CHARACTER RECOGNITION(OCR):‘Its the mechanical or electronic conversion of scanned images of handwritten, typewritten or printed text into machine-encoded text’.
Key points of (OCR):
Scanner with a character recognition software (called OCR software) that converts the bit map images of characters to ASCII codes.
Enables word processing of input text and also requires less space for storing the document .
OCR software is extremely complex because it is difficult to make a computer recognize an unlimited number of fonts
Two standard OCR fonts are OCR-A (American standard) and OCR-B (European standard).
BAR CODE READER: ‘A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes’.
Key points of Bar Code Reader :
Scanner used for reading (decoding) bar-coded data.
Bar codes represent alphanumeric data by a combination of adjacent vertical lines (bars) by varying their width and the spacing between them.
Scanner uses laser-beam to stroke across pattern of bar code. Different patterns of bars reflect the beam in different ways sensed by a light-sensitive detector.
Universal Product Code (UPC) is the most widely known bar coding system.
OPTICAL MARK READER (OMR):‘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’.
key points of (OMR):
Scanner capable of recognizing a pre-specified type of mark by pencil or pen
Very useful for grading tests with objective type questions, or for any input data that is of a choice or selection nature
