Computer 11 Notes for Computer Notes

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Input Devices

Some of the input devices used in a computer are keyboard, mouse scanner, joystick, touch screen, touchpad, track ball, bar code reader, light pen, optical code reader (OCR), MICR, OMR, microphone, digital camera, webcam, card readers, digitizing tablets, etc.


Keyboard is the most basic input device. It is used for text input. It contains multiple keys. User can provide input by pressing the key. The different types of key found in keyboard are:

  1. Alphanumeric keys (A-Z, 0-9)
  2. Function keys (Ctrl, Alt, Caps lock, Enter, Tab, Shift)
  3. Special function keys (F1, F2, F3,……..,F12)
  4. Cursor movement keys (?, ?)
  5. Punctuation keys (,, “” , ’’, ?, !)
  6. Numeric pad
  7. Multimedia keys

On the basis of keys, keyboard can be classified as

  1. XT keyboard -83 keys
  2. AT keyboard -101 keys
  3. Enhanced keyboard -103 and more keys

A keyboard contains an electronic circuit known as keyboard encoder. This circuit detects the pressed key, generates its electronic signal and transmits towards CPU.
On the basis of connectivity, keyboard can be wire or wireless.


Mouse is a most common pointing and selecting device. It is used in graphical user interface. Mouse contains buttons for providing inputs. User can provide inputs by moving the mouse and pressing the button. On the basis of buttons, mouse can be:

  1. Two-buttoned mousse
  2. Three-buttoned mouse

Usually, the left button of the mouse is for normal selection and the right button is used for special function and central button is used for scrolling a document.
On the basis of working mechanism and its architecture, mouse can be classified as:

  1. Mechanical mouse
  2. Opto-mechanical mouse
  3. Optical mouse

Mechanical mouse contains a rubber ball and a pair of rotating wheels. When the mouse is moved on the table, the ball rotated which results in rotation of the wheels and generates electronic signal.
Optical mouse operates using reflection of light. It is easier to use but usually less reliable than mechanical mouse.
The opto-mechanical mouse contains both mechanical and electric component.

Track ball
Trackball is the modification of mechanical mouse. It contains rubber ball on its top. User can move the cursor by rotating the ball with finger. It also contains two buttons on the either sides similar to mouse. It was used in older laptops.

Track pad/Touch pad

Track pad is the modification of optical mouse, and touch pad is further modification making it touch sensitive. It contains a window with two buttons on the either sides. User can also provide left click option by tapping the window with the finger. It is mainly used in portable devices like laptops, notebook, palmtop, etc.


Joystick is a hand held pointing device which is mainly used for playing games. It is used for controlling objects, their movement, direction and speed of movement. Modern joysticks handle can move in any direction. When the handle is moved, the electronic circuit in the base detects the movement and sends corresponding binary signals to CPU.

Light pen

Light pen is used for creating drawings, designs by directly touching the screen. It is mainly used by designers, architects, engineers, etc. it is used in monitor not having touch screen facility. It is a pen shaped structure containing photo sensitive tip which can capture light emitted from the monitor and mark the position on the monitor.

Touch screen

Touch screen is none of the common input device at present mainly for portable computers. User can provide inputs by directly touching the screen with the metallic pen (stylus), finger or any pointed object. Touch screen is developed by using either of the following technologies:
a) Pressure sensitive
b) Capacitive
c) Infrared


Scanner digitizes hard copy or printed images which can be used in digital computers. Scanner copies the image and draws a new digital image in its memory similar to hard copy image.

OCR (Optical Character Reader)

OCR digitizes handwritten or printed text.
Printed text will have fewer errors than hand written. It directly converts hand written text into digital text which can be edited. OCR contains predefined format of all the characters. During digitizing process, it creates an image of the character and compares it with stored format to determine the character.


It stands for Magnetic Ink Character Reader. MICR is an OCR that can digitize text written or printed by using magnetic ink like iron oxide or barium ferrite. It is used in security systems and for processing cheque in bank.


It stands for Optical Mark Reader. It is used for answer sheet correction in multiple choice questions. With the use of OMR answer sheet correction will be faster and error free.


It stands for Bar Code Reader. Bar codes are the magnetic lines used for storing the information about the product like manufacturing date, expiry date, company name, etc. BCR is used to read the information stored in bar codes. Bar codes are also used in security system.


It is an input device for sound. It captures sound wave, converts it into digital format and provides it to the CPU. Common mobile computing devices like PDA, smart phone contains microphone.

Digital camera, Web camera

Digital camera captures real time images and video and stores it in a digital format. The image captured by digital camera can be directly used in a digital camera.

Web camera is a digital camera used in internet. It usually captures low quality images so that it could be transmitted at a faster speed.

Card reader

It is used to read the information stored in cards like ATM card, Credit card, Smart card, etc.

Digitizing tablet

It is used to digitize large map or hardcopy images. It is also used to track the movements of living beings and capture them in digital format.

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