ReggaetonKing

I just finished my first college course as a freshman, I am taking CSE 210 Machine and Assembly Language. So far so easy, 0_o Anyway, the instructor was going over binary digits and such. He was saying that every byte has a 9th bit which is called a 'parity'. And the reason for the partiy is that number of bits that are on in each byte must be always odd, if not the processor forces odd partiy by automatically setting the parity bit on. Says ok to me but why?

Why exactly does the number of bits in a byte that are 'on' have to be odd. I spend two hours wondering about that question and the instructor said he didn't want to go in "complex hardware details, so for now, it just does!". Some one please explain this to me.

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