Need I say more ?

Who uses 1s complement anyway ?

https://stackoverflow.com/questions/1099276/why-base-2-with-binary-numbers

"CDC used to produce 1's complement machines which made negation very easy as you suggest. As I understand it, it also allowed them to produce hardware for subtraction that didn't infringe on IBM's patent on the 2's complement binary subtractor."
edited Oct 18 '12 at 19:05 by NullUserException

Because of this, 1's complement has crept into some languages up until the 80's, such as VHDL (derived from Ada, derived from Pascal, "because we want the language to run everywhere we can"), creating confusion and facepalms for decades...