There are many control characters which are not defined in
unicode. The serve many different, very specific purposes, like
Videotex applications or bibliographic storage references. It is
totally outside this library to deal with the interpretation of them.

Each time a control character is found and which is not one of those
defined in ISO 2022 to select another character set, they are
interpreted as far as needed to find out how many parameter bytes must
not be transformed. The control characters themselves are returned by
an integer corresponding to the enum (iso2375.h) and offset by a
constant which can be selected. By default, this constant is U+F0000,
the starting point of a private unicode area. Selection of the offset
is done just by writing it to the struct which is returned by the
interpreter function.