The Unicode characters can be categorized in many different ways. Unicode code points can be logically divided into 17 planes, each with 65,536 (= 216) code points. Planes are identified by the numbers 0 to 16decimal, which corresponds with the possible values 00-10hexadecimal of the first two positions in six position format (hhhhhh). Six of these planes also have names. Sometimes, terms “astral plane” and “astral characters” are used informally to refer to the planes above the Basic Multilingual Plane (i.e., planes 1, 2… 16) and their characters.