An octal-escape-sequence is a backslash followed by 1, 2, or 3 octal digits. '\0' is just another octal escape sequence, not a special-case syntax for the null

An octal-escape-sequence is a backslash followed by 1, 2, or 3 octal digits. '\0' is just another octal escape sequence, not a special-case syntax for the null character. "\0", "\00", and "\000" all represent the same value; "\0000" is a string literal containing a null character followed by the digit '0'. Hexadecimal escape sequences can be arbitrarily long. If you need a string containing character 0x12 followed by the digit '3', you can write "\x12" "3".