In double-byte character sets (DBCS) the internal representation for each character requires two bytes of storage. Writing systems such as Kanji and Chinese require such double-byte representations. In some cases, the Katakana writing system is considered a single-byte character set (SBCS) because it can be represented internally in single bytes. English, German, and French languages fit the category of single-byte character sets.
References made in this chapter to "mixed" data mean that strings of DBCS data and strings of SBCS data appear in one data field. When data is mixed, the DBCS data is preceded by an SO (shift out) delimiter character and followed by an SI (shift in) delimiter character. If you enter DBCS data in a field, you need not enter SO and SI; they are automatically generated by the hardware when DBCS data is used. Because SO and SI are delimiters, not real characters, the data contained between them is interpreted as double-byte.