Everyone has seen barcodes, on groceries, newspapers and virtually every other product that they buy, but how many people know what they mean? I have always felt that one day I ought to sit down and work out what the various stripes in the barcodes meant – they were an obvious challenge. However, on the various occasions when I have tried, I have had no success, and I have given up (and as you will see from what follows, the system is sufficiently complex that a simple attack on the coding system is unlikely to succeed).