>
> But there are *dozens* of different barcode coding schemes - surely they
> don't all use the same codes at the
> ends?


Nope, but the one that the public thinks is done this way is UPC/EAN.

AFAIK there is NO symbology where 6's are used as end sentinels.
In Code 39, *s are, but even in this case, there's no "middle".

In UPC/EAN, you have the numbers printed below, and it's easy to get the
(wrong) idea that the 111 triplet encodes a six, missing the 4 that follows
or precedes it.  Then you look at the guard bars and center guard, and see
the 111 pattern there again.

The UPC/EAN symbology encoding is brilliant. There are so many ways built
into it to help eliminate false reads, it's really impressive.  I don't mean
scans that don't decode here, I mean scans that decode to the wrong output.
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