Why do computers use binary

3)
- Analog Signal- a signal thats proportional to the value it represents
-your head phone jack saplies voltage to the head phone wire
-when the sound is at high pressure the phone has a high voltage, when the sound is at a low pressure the phone has a low voltage  

2)
-Digital signal
-the adder

1)
-one thing I would like to know more about is the adder