One's Complement, Two's Complement

https://www.youtube.com/watch?v=Z3mswCN2FJs

"Two's complement successfully solves the problem of storing and manipulating negative numbers,
but recognize that, by sacrificing the first bit for flagging the sign, we are change the range of numbers we can represent. Four bits can represent the numbers 0 through 15 without a signed bit, and -8 through positive 7 with a sign bit. "