In binary, where there are two states, "NOT" or any variation thereof (~ ! etc) reverses the bit value, so... NOT 1 = 0. It makes sense on a bit level... if it's NOT a zero, it must be a one, yes? Now, of course if it is not, not a one, then it was all along a zero. In comedy, the "double negative" can lead to all sorts of Don Knott's style of humor - in computer science... not so much.