The document lists and describes various common computer input devices, including keyboards, mice, joysticks, light pens, trackballs, scanners, graphic tablets, microphones, magnetic ink card readers, optical character recognition, bar code readers, and optical mark readers. It provides details on how keyboards, mice, and scanners function, with keyboards transmitting scan codes when keys are pressed and mice using ball movement to generate electrical pulses that move the cursor. Scanners convert printed text and graphics into digital form using a light sensor, usually a CCD, to detect light reflected from documents.

1. THE FOLLOWING IS A LIST OF THE MOST COMMON INPUT
DEVICES WHICH ARE NOWADAYS FOUND IN A COMPUTER SYSTEM:
1ST KEYBOARD
2ND MOUSE
3RD JOY STICK
4TH LIGHT PEN
5TH TRACK BALL
6TH SCANNER
7TH GRAPHIC TABLET(DIGITIZER)
8TH MICROPHONE
9TH MAGNETIC INK CARD READER(MICR)
10TH OPTICAL CHARACTER READER(OCR)
11TH BAR CODE READER
12TH 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.

2. 1st KEYBOARD................/.

3. 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
are
generally give same layout as that of typewriters.
2. NUMERIC
KEYS
I t is used to enter numeric data or cursor movement. Generally, it
consists
of a set of 17 keys that are laid out in the same configuration used by
most
adding machine and calculators.
3. FUNCTION
KEYS
The twelve functions keys are present on the keyboard. These are
arranged
in a row along the top of the keyboard. Each function key has unique
meaning and is used for some specific purpose.
4. CONTROL
KEYS
These keys provides cursor and screen control. I t includes four
directional
arrow 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.

4. Working of keyboard:
WORKING OF
KEYBOARD.......
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

5. 2nd MOUSE:
MOUSEISAHANDHEALDDIVICETHATALLOWSUSERTOMOVEITEMSON
THESCREEN.

6. 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.

7. 3rd Joystick:
‘Joystick is also a pointing device which is used to move
cursor position on a monitor screen. ’

8. 4th LIGHT PEN:
‘they are pen shaped devices are used to select the screen icons by detecting
the light coming from the CRT screen.’

9. 5th TRACK BALL:
A trackball is a stationary pointing device with a ball
mechanism
on its top.

10. 6th SCANNER:
‘Ascanner is a light-sensing input device that convertsprinted text and
graphicsinto a digital form that can be furtherprocessed by the computer’

11. TYPES OF SCANNER:
1.flat bed scaner,2.hand held
scanner

12. 2nd hand held scanner:

13. 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.

14. 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’.

15. MICROPHONE:
‘a microphone is an input device that convert sound into electrical
signals’.

16. 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’.

18. OPTICAL CHARACTER
RECOGNITION(OCR):
‘Its the mechanical or electronic conversion of scanned images of
handwritten, typewritten or printed text into machine-encoded text’.

19. BAR CODE READER:
‘A barcode reader (or barcode scanner) is an electronic device for
reading printed barcodes’.

20. 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’.

21. OMR SHEET: