(American National Standard for Extended Latin Alphabet Coded Character Set for Bibliographic Use) is an encoding used in genealogy software, most notably GEDCOM. It is an 8 bit encoding designed to provide a way to print latin with full integrity.
The encoding makes use of non-spacing character modifiers to print multiple characters on top of one another, so that latin can be easily printed with all it’s diacritics. It is a superset of ASCII, thus ANSEL is an addition to ASCII encoding. ANSEL requires that diacritics precede the character that is to be modified.