CHAPTER 3
56
Syntax
values. Note that the backslash character is still required as an escape to specify
unbalanced parentheses or the backslash character itself.
Hexadecimal Strings
Strings may also be written in hexadecimal form, which is useful for including
arbitrary binary data in a PDF file. A hexadecimal string is written as a sequence
of hexadecimal digits (
0
–
9
and either
A
–
F
or
a
–
f
) enclosed within angle brackets
(
<
and
>
):
< 4E6F762073686D6F7A206B6120706F702E >
Each pair of hexadecimal digits defines one byte of the string. White-space
characters (such as space, tab, carriage return, line feed, and form feed) are
ignored.
If the final digit of a hexadecimal string is missing—that is, if there is an odd
number of digits—the final digit is assumed to be
0
. For example:
< 901FA3 >
is a 3-byte string consisting of the characters whose hexadecimal codes are
90
,
1F
,
and
A3
, but
< 901FA >
is a 3-byte string containing the characters whose hexadecimal codes are
90
,
1F
,
and
A0
.
3.2.4 Name Objects
A
name object
is an atomic symbol uniquely defined by a sequence of characters.
Uniquely defined
means that any two name objects made up of the same sequence
of characters are identically the same object.
Atomic
means that a name has no
internal structure; although it is defined by a sequence of characters, those
characters are not considered elements of the name.
A slash character (
/
) introduces a name. The slash is not part of the name but is a
prefix indicating that the following sequence of characters constitutes a name.
There can be no white-space characters between the slash and the first character