C Character Constants
A "character constant" is formed by enclosing a single character from the representable character set within single quotation marks (' '). Character constants are used to represent characters in the execution character set.
character-constant: ' c-char-sequence '
L' c-char-sequence '
c-char: Any member of the source character set except the single quotation mark ('), backslash (\), or newline character
simple-escape-sequence: one of \a \b \f \n \r \t \v
\' \" \\ \?
octal-escape-sequence: \ octal-digit
\ octal-digit octal-digit
\ octal-digit octal-digit octal-digit
hexadecimal-escape-sequence: \x hexadecimal-digit