说明：  格雷码，Gray Code,，是一种绝对编码方式，典型格雷码是一种具有反射特性和循环特性的单步自补码，它的循环、单步特性消除了随机取数时出现重大误差的可能，它的反射、自补特性使得求反非常方便。
(Gray Code, Gray Code,, is an absolute encoding, the typical Gray code is a kind of reflection characteristics and cycle characteristics of the single-step self-complement, and its circulation, single-step feature eliminates the number of randomly selected major errors when possible, it' s reflective, anti-self-complementary features make the demand is very convenient.)