Explain the function of light pen and joystick

Explain the function of light pen and joystick?

Answer:

LIGHT PEN

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
screen.

JOYSTICK

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.