Common Lisp the Language, 2nd Edition
Characters are represented as data objects of type character.
There are two subtypes of interest, called standard-char and string-char.
X3J13 voted in March 1989 (CHARACTER-PROPOSAL) to remove the type string-char.
A character object can be notated by writing #\ followed by the character itself. For example, #\g means the character object for a lowercase g. This works well enough for printing characters. Non-printing characters have names, and can be notated by writing #\ and then the name; for example, #\Space (or #\SPACE or #\space or #\sPaCE) means the space character. The syntax for character names after #\ is the same as that for symbols. However, only character names that are known to the particular implementation may be used.