13.1.9 Character Encodings

A character is sometimes represented merely by its code, and sometimes by another integer value which is composed from the code and all implementation-defined attributes (in an implementation-defined way that might vary between Lisp images even in the same implementation). This integer, returned by the function char-int, is called the character’s “encoding.” There is no corresponding function from a character’s encoding back to the character, since its primary intended uses include things like hashing where an inverse operation is not really called for.