I/O devices are the piece of instrument of hardware through which human can contact with computer.
Input Devices:
a) Graphics Tablets
graphics tablet is a input device which help user to draw image,animation,graphics like pencil like stylus
b) Cameras
c) Video Capture Hardware
is a process of converting analog system to digital system
d) Trackballs
it is a input device.used as a alternative of mouse as well as move the cursor of the screen
e) 
Barcode reader:it can read and printed output
f) Digital camera
g) Gamepad
h) Joystick
A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling
i) Keyboard
j) Microphone
k) MIDI keyboard
l) Mouse (pointing device)
m) Scanner
n) Webcam
o) Touchpads
p) Pen Input
q) Microphone
r) Electronic Whiteboard
s) OMR
t) OCR
u) Punch card reader
v)MICR (Magnetic Ink character reader)
w) Magnetic Tape Drive
I loved game
Nice information about input and output devices of a computer system...