ESC is the ASCII character for code extension. ISO 2022 aka ECMA-35¹ standardizes how to use it in general, but the only thing that really caught on is a subse

ESC is the ASCII character for code extension. ISO 2022 aka ECMA-35¹ standardizes how to use it in general, but the only thing that really caught on is a subset of the terminal control extensions (ISO 6429 aka ECMA-48² aka ‘ANSI’). In the hypothetical alternate universe where people use ASCII-based structured data, ISO 2022 would have standard sequences for such metadata. If you were rolling your own today, you'd probably wrap the metadata in Application Program Command (ESC _ … ESC \) or Start Of String (ESC X … ESC \) or one of the private-use sequences. ¹ https://www.ecma-international.org/publications/standards/Ecma-035.htm https://www.ecma-international.org/publications/standards/Ec... ² https://www.ecma-international.org/publications/standards/Ecma-048.htm https://www.ecma-international.org/publications/standards/Ec...