The structure of EUC is based on the standard, which specifies a system of graphical character sets which can be represented with a sequence of the 94 7-bit bytes 0x21–7E, or alternatively 0xA1–FE if an eighth bit is available. This allows for sets of 94 graphical characters, or 8836 (942) characters, or 830584 (943) characters. Although initially 0x20 and 0x7F were always the space and and 0xA0 and 0xFF were unused, later editions of allowed the use of the bytes 0xA0 and 0xFF (or 0x20 and 0x7F) within sets under certain circumstances, allowing the inclusion of 96-character sets. The ranges 0x00–1F and 0x80–9F are used for C0 and C1 control codes.