<code>\U</code> followed by exactly eight hexadecimal digits, and a
plain backslash <code>\</code> followed by exactly three octal digits.
In each case the value of the literal is the value represented by
the digits in the corresponding base.
</p>

<p>
Although these representations all result in an integer, they have
different valid ranges.  Octal escapes must represent a value between
0 and 255 inclusive.  Hexadecimal escapes satisfy this condition