The excape sequence \ddd consists of a backslash followed by one, two, or three octal digits that specify the value of the desired character.

The escape sequence \xdddd consists of a backslash followed by the character x and one, two, three, or four hexadecimal digits that specify the value of the desired character. Note that the hexadecimal coding sequence is an extension to X/Open UNIX CAE specifications and therefore may not be supported on other systems that conform to these specifications.