A special character is any character that is not contained in the following list:
• Characters that indicate the end of a line in a file
A digit is a character.
<digit> ::= 0 | 1 | 2 | | 3 | 4 | 5 | 6 | 7 | 8 | 9
A letter is a character.
<letter> ::= A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
| a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z
An extended letter is a character.
<extended_letter> ::= # | @ | $
A hex_digit is a character.
<hex digit> ::=
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
| A | B | C | D | E | F
| a | b | c | d | e | f
A language-specific character is any letter that occurs in a northern, southern, or central European language and is not contained in the list of letters.
German umlauts: ä, ö, ü
French letters with a “grave” accent.
If you have installed a UNICODE-enabled database, a language-specific character is a character that is not included in the ASCII-Code list from 0 to 127.