Input Unit:
An input is a device of computer which feeds data to the computer. Raw data are entered into a computer through an input unit, which is also called an input device. An input device converts the input into a suitable form acceptable to a computer.   

For examples, we can see below picture:

    1.    Keyboard, 
    2.    Mouse, 
    3.   Scanner,
    4.   Trackball, 
    5.   Web camera,
    6.   Light pen, 
    7.   BCR (Bar Code Readers), 
    8.   OCR (Optical Character Recognition), 
    9.   MICR (Magnetic Ink Character Recognition), 
    10.   Touch screen, 
    11.   Joystick,  etc.

Keyboard

           Mouse

Scanner