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Explain the function of light pen and joystick?


Alight pen is an input device that uses a light sensitive stylus connected by a
 wire to a video terminal. The user brings the light pen to the desired point on the screen surface
 and presses a button, causing it to identify the location on the screen. Light pens are used to
 select the options from a menu displayed on screen or to draw images in graphics system by

  “dragging” the cursor around the screen. The pixels (dots) on a display screen are constantly
 being refreshed (re-illuminated) over again. When the user presses the light pen button,
 allowing the pen to sense light, the pixels being illuminated at the movement identifies on the


A joystick is an omni-directional level that is used to move the cursor on screen
 more rapidly then it can be moved with the directional arrow keys. It has a spherical ball at
 its lower end as well as its upper end. The lower spherical ball moves in a socket. Thus, a
 joystick can be moved right or left, forward or backward. The electronic circuitry inside the
 joystick detects and measures the displacement of the joystick from its central position. This
 information is sent to CPU. The pointer on the CRT screen moves according to the position
 of the joystick. The joystick is used extensively in video games, but is also used as an input
 device in computer aided design (CAD) systems.

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