CHAPTER 3
50
Syntax
TABLE 3.1 White-space characters
DECIMAL
HEXADECIMAL
OCTAL
NAME
0
9
10
12
13
32
00
09
0A
0C
0D
20
000
011
012
014
015
040
Null (NUL)
Tab (HT)
Line feed (LF)
Form feed (FF)
Carriage return (CR)
Space (SP)
The carriage return (CR) and line feed (LF) characters, also called
newline
characters,
are treated as
end-of-line
(EOL) markers. The combination of a
carriage return followed immediately by a line feed is treated as one EOL marker.
For the most part, EOL markers are treated the same as any other white-space
characters. However, sometimes an EOL marker is required or recommended—
that is, the following token must appear at the beginning of a line.
Note:
The examples in this book illustrate a recommended convention for arranging
tokens into lines. However, the examples’ use of white space for indentation is purely
for clarity of exposition and is not recommended for practical use.
The
delimiter characters
(
,
)
,
<
,
>
,
[
,
]
,
{
,
}
,
/
, and
%
are special. They delimit
syntactic entities such as strings, arrays, names, and comments. Any of these
characters terminates the entity preceding it and is not included in the entity.
All characters except the white-space characters and delimiters are referred to as
regular characters.
These characters include 8-bit binary characters that are
outside the ASCII character set. A sequence of consecutive regular characters
comprises a single token.
Note:
PDF is case-sensitive; corresponding uppercase and lowercase letters are con-
sidered distinct.