ANSI Common Lisp 13 Characters 13.1 Character Concepts
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
(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
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.