8.2.3 External Representations
An important concept in the expression language (and Lisp) is that of the external representation of an object as a sequence of characters. For example, an external representation of the integer 28 is the sequence of characters 28, and an external representation of a list consisting of the integers 8 and 13 is the sequence of characters (8 13).
The external representation of an object is not necessarily unique.  The list in the previous paragraph also has the representations ( 08 13 ) and (8 . (13 . ())).
Many objects have external representations, but some, such as procedures, do not.
An external representation may be written in an expression to obtain the corresponding object.
External representations may also be used for communicating between processes defined in this International Standard.
The syntax of external representations of various kinds of objects accompanies the description of the primitives for manipulating the objects.