Bar codes. They're little bunches of black lines which can be read by a 
scanner. Right?

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

I just did a cursory scan of my office. Here's what I found:

   Fruit bottle: EAN-13 barcode.
   Can of Dust-off: UPC-A barcode.
   Diary: EAN-13 barcode.
   SIIG USB-serial box: UPC-A barcode plus one of unknown type.
   StarTech USB-serial box: UPC-A barcode.
   Imation CD-R box: UPC-A barcode.
   Maxtor drive: 5 barcodes of unknown type.
   Integral RAM box: One barcode (from Insight UK) of unknown type.
   TNT shipping box: Two barcodes of unknown type.
   Gobel, Escher, Bach: EAN-13 barcode.
   Integral USB HD box: EAN-13 barcode.
   Other USB HD box: EAN-13 barcode.
   HP laptop adaptor: 3 barcodes of unknown type.

It's actually surprisingly hard to find barcodes. Usually you purposely 
ignore them, so when you *want* to see them they're actually quite hard 
to find.

It's great fun. EAN-13 is apparently an "extension" of UPC-A, and yet 
it's COMPLETELY DIFFERENT. The encoding is entirely unrelated. Of 
course, EAN-13 and UPC-A only encode digits. (And these digits encode a 
manufacturer ID and product ID.) Other codes can encode various 
additional characters. In particular, Code39 and Code128 allow text as 
well as digits.

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...

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