DoubleByte

DoubleByte is a term used in computing to refer to character encoding schemes that use two bytes per character to represent a large set of symbols beyond the 256-character limit of ASCII. The expression is commonly associated with the family of double-byte character sets (DBCS) developed to support East Asian languages.

Double-byte encodings typically allocate ranges of byte values to indicate lead bytes and trail bytes, allowing thousands of characters to be defined. The exact structure varies by scheme. Examples historically used in software include GB2312/GB18030 for Chinese, Big5 for Chinese, Shift JIS and EUC variants for Japanese, and KS C 5601 for Korean. Some encodings commonly used in DBCS contexts encode most characters as two-byte sequences, while others mix one- and two-byte representations within a single code page.

Today Unicode has become the dominant system for general-purpose character encoding, using 1 to 4 bytes per code point. DBCS remains in use primarily for legacy data, software, and certain code pages in operating systems such as Windows, where specific locales rely on two-byte encodings for compatibility with existing text data.

As a term, DoubleByte also appears as a potential brand name or product label in various contexts, but there is no single, universally recognized organization or standard formally titled "DoubleByte."