Invisible wrote:

> Hahaha, well... it turns out there are actually a miriad of different 
> kinds. And they're ALL COMPLETELY DIFFERENT to each other.

Interestingly, though, they all seem to have quite characteristic 
start/end markers. It appears to be possible to uniquely discriminate 
them by this alone.

(For example, UPC-A and EAN-13 both start and end with ...01010...)

> I just did a cursory scan of my office.

I see what I did there. ;-)

> Here's what I found:
> 
>   SIIG USB-serial box: UPC-A barcode plus one of unknown type.

This appears to be Code-39. (Begins 10010... and ends ...0101101101.) 
I'm guessing it encodes the serial number also printed above the barcode.

>   Maxtor drive: 5 barcodes of unknown type.

These all appear to be Code-128. (Begins 11010... and ends ...11101011.)

>   Integral RAM box: One barcode (from Insight UK) of unknown type.

This seems to be Code-39 again. (I'm guessing it encodes the large part 
number printed above, not the smaller description text.)

>   TNT shipping box: Two barcodes of unknown type.

I no longer have the box.

>   HP laptop adaptor: 3 barcodes of unknown type.

Two of these appear to be Code-39. The final one might be Code-93. Maybe.

> It's great fun. EAN-13 is apparently an "extension" of UPC-A, and yet 
> it's COMPLETELY DIFFERENT. The encoding is entirely unrelated.

 From what I can tell, the two utterly different algorithms are supposed 
to produce the same output in the case of an EAN-13 where the extra 
digit happens to be zero. I haven't varified how this is possible yet.

> The impressive thing is, as far as I can tell, almost all barcode 
> scanners support almost all kinds of barcodes. Even though each coding 
> scheme is utterly unrelated to any of the others. God only knows how 
> this is physically possible...

Again, it appears the start and stop markers are actually pretty unique 
to each barcode type. It seems to be possible to distinguish them by 
that alone, without the aid of a computer...

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