Question

what role do input unit and output unit play in a computer

Answer 1

Input unit takes the instructions from a user in the form of electronic signals and then CPU converts in into machine language(a language which is understandable by a computer)
Then the CPU sends the completed instructions in the form of electronic signals to the Output unit which converts the signals into human understandable form

Answer 2

Input unit is the one which takes the information. Output unit is the one which gives us the information example of input unit keyboard, mouse.output unit are joystick,scanner monitor etc.