ISO/IEC 2022

ISO/IEC 2022 Information technology—Character code structure and extension techniques, is an ISO standard (equivalent to the ECMA standard ECMA-35) specifying

• a technique for including multiple character sets in a single character encoding system, and
• a technique for representing these character sets in both 7 and 8 bit systems using the same encoding.

Many of the character sets included as ISO/IEC 2022 encodings are 'double byte' encodings where two bytes correspond to a single character. This makes ISO-2022 a variable width encoding. But a specific implementation does not have to implement all of the standard; the conformance level and the supported character sets are defined by the implementation.