An extension of the ISO 646 version 7-bit structure to an 8-bit structure. The IBM PC single-byte structure has a valid code point range for 00 to FF. The graphic characters have the following range: The first byte is in the range 81 to FC. The second byte is in the range X'40' to X'7E' and X'80' to X'FC'. No other 16-bit patterns are valid as graphic characters.