\ OctalDigit etc.

[Moritz Warning]

This was probably discussed before.
But I run into a problem when I was checking
for missing characters in a long string sequence since some application 
kept telling me that it was invalid.

The point was that \012 is not '\0' '1' '2' but one char '\012'.
other representations with hexadecimal numbers have an
alphabetical char to indicate smth. special might follow (\xaa).

In my case thinking of \0 being the same as single char and in a string
was wrong.
This is inconsistent and I think many could get wrong as I did.

I don't have much hope to get a convenient solution as for hexadecimal 
representations.
But I thought I just post this for others who stumble over the same 
stone. :/