Acronym for American Standard Code for Information Interchange.
ASCII is a common numerical code for computers and other devices that use text. As computers can only understand numbers, an ASCII code will use a number (e.g. 99, 63) to represent a character (e.g. ‘c’, ‘?’) using a number. When mentioned in relation to domain names or strings, ASCII refers to the fact that before internationalisation only the letters (a-z), digits (0-9), and the hyphen (-), were allowed in domain names.