ISO88594

ISO/IEC 8859-4, commonly referred to as Latin-4, is part of the ISO/IEC 8859 family of eight-bit single-byte character encodings. Like other encodings in the family, it reserves the first 128 code points for ASCII and uses the remaining 128 for additional characters.

Latin-4 is designed for North European languages and adds letters with diacritics used in Danish, Norwegian, Swedish, Icelandic, Finnish, and the Baltic languages such as Estonian, Latvian, and Lithuanian. It provides the accented Latin letters needed by these languages that are not present in plain ASCII.

Technically, it is a single-byte encoding with an 8-bit code space, and it is a stateless encoding in which each byte maps to exactly one character. It does not define multi-byte sequences or combining characters as part of its core design. The upper half of the code table (0xA0–0xFF) contains the Latin letters with diacritics and other symbols necessary for its target languages.

Latin-4 was published in the 1980s as part of the broader effort to support internationalization before Unicode became prevalent. Today, its use is largely confined to legacy data and systems. UTF-8 and Unicode have largely supplanted ISO-8859-4 for new text, though some older documents, mail archives, and software may still rely on this encoding or assume it in data interchange.

Mapping to Unicode is defined so that each code point in 0xA0–0xFF corresponds to a specific Unicode code point, facilitating conversion between Latin-4 and Unicode-based systems. See also the ISO/IEC 8859 family, Unicode, and UTF-8.