Who developed the binary number system?

Answer 1

'Yes/No' type systems have been used for millennia eg in India, China. I think Leibniz was the first modern mathematician to write explicitly about '1-0' in the 18th Century, followed by George Boole's paper on logic systems (1854?) which eventually became known as Boolean algebra. "There are 10 types of people in the world - those who understand binary and those who don't"

Answer 2

The modern binary number system was fully documented by Gottfried Leibniz