Editing Unicode (section)

=== Code planes and blocks ===
{{Main|Plane (Unicode)}}

The Unicode codespace is divided into 17 ''planes'', numbered 0 to 16. Plane 0 is the [[Basic Multilingual Plane]] (BMP), and contains the most commonly used characters. All code points in the BMP are accessed as a single code unit in UTF-16 encoding and can be encoded in one, two or three bytes in UTF-8. Code points in planes 1 through 16 (the ''supplementary planes'') are accessed as surrogate pairs in [[UTF-16]] and encoded in four bytes in [[UTF-8]].

Within each plane, characters are allocated within named ''[[Block (Unicode)|blocks]]'' of related characters. The size of a block is always a multiple of 16, and is often a multiple of 128, but is otherwise arbitrary. Characters required for a given script may be spread out over several different, potentially disjunct blocks within the codespace.