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write a short note on input and output of a computer with pictures?

Input devices: There are used to enter data to the computer system. The input devices are also responsible for translation of data to a form that the computer system can understand.

Output Devices: These are used to communicate the processed information to the user. Output devices translate the processed data into a form that can be interpreted by humans.

Keyboard is the most widely used devices to input information in the form of words, numbers, etc. A standard keyboard includes all the keys found on a typewriter plus some additional keys, usually 105 keys. Many types of keyboards are now available.

Keyboard is the most widely used device to input information in the form of words,numbers etc.Computer keyboard are similar to typewriter keyboards but contain some additional keys.

There are 101 keys on a standard key board .The keys on the keyboard are often classified into standard typewriter keys,function keys,special purpose keys ,cursor movement keys and numeric keys.The type writer keys are used to type in text and other data.The function keys labelled F1 to F12 are used to issue commands.Computer keyboards also have some special purpose keys such as Insert,Delete ,Ctrl,Alt etc.

Mouse 

OMR

Optical Mark Reader (OMR) is a technology where the OMR device senses the presence and absence of a mark such as pencil mark. OMR is commonly used in objective type test for inputting data recorded on questionnaires.

MICR

MagneticInk Character Recognition (MICR) allows the computer to recognise characters printed in a special font.It is used in banks to read the numbers on the cheques directly,so that it reduce the errors.

OCR

Optical Character Recognition (OCR).It is a device  that can read characters printed with a predefined font .Each character is recognized by optical scanning,digitizing,followed by analysis of the printed pattern. 

Bar code reader

Bar Code Readers are photo electric scanners that read the bar codes or vertical zebra striped marks printed on product container.A bar code is used to identify the description and price of a product to the super market's computer.

Track ball

Track ball is  a pointing device in the shape of a mouse lying on its back.It is used in portable computers.

Light pen

Light pen is an input device that utilizes a light sensitive detector to select objects directly on a display screen using a pen.It ha s photocell placed in a small tube.When the pen is moved over the screen surface,it is able  to detect the light coming from the screen.

Light pens are frequently used by graphics designers,illustrators and drafting engineers using Computer Aided Design(CAD) to draw directly on the screen.

Scanner

Scanner is an input device that can read text or picture on paper and translate the information into computer usable form.

A Scanner works by dividing an image into grid of boxes that represents each box with a zero or one depending on whether the box is filled in. Each box is represented by upto 24 bits.

Digital Camera

Images can be input into a computer using digital camera.The digital camera can take still photographs and store it.The image can be transferred as digital input into the computer.

Output devices:

An output device is any machine capable of representing information from a computer.Output devices can be classified into hard copy devices and softcopy device

Visual display units.

The terminal that use video screens are commonly called visual display units(VDU).

The most common VDU is the Cathode Ray Tube(CRT) , Liquid Crystal Display (LCD) and Plasma screen.

Printer

The devices used to produce hard copy of output data or text are known as printers. The two categories of printers are impact and non – impact.