Black, white and read all over
		Barcodes are everywhere: from cans of Coke to aircraft parts. But what do the stripes really stand for? Financial Times The Business Magazine, July 14, 2001 Illustration by David Newton Used to fight the spread of problems such as counterfeit aircraft parts, as well as to catalogue the everyday shopping experience, the barcode’s influence is everywhere. Some even believe that all barcodes contain the number of the beast, “666”. Initially proposed in 1932, it wasn’t until 1972 that a Kroger supermarket in Cincinnati became the first store to use barcodes to automate its check-outs. The Kroger system was based on a series of concentric circles of different thicknesses. This was replaced in 1973 by the more economical rectangular bar system, known as Universal Product Code or UPC, and on June 26 1974, a box of Wrigley’s Spearmint Gum became the first consumer item to be UPC scanned. The age of the barcode had truly begun. The UPC system is made up of 12 digits, divided into two halves. Digits on the left half are encoded differently from those on the right, preventing the reader from scanning back-to-front. By 1976, though, most available numbers had been used by US companies. To expand the system to the rest of the world, a 13th digit was added at the left-hand end. US numbers could be converted to the new system – known as European Article Numbering (EAN)-13 – by adding a 0. The rest of the world was then able to use all remaining 13-digit numbers beginning 1-9. The extra digit was encoded by giving each remaining digit in the left half of the barcode (ie those in positions 2 to 7) two alternative encodings – A and B. By looking at which encoding is used for each digit, a scanner can calculate the value of the extra digit without its having to have a set of bars of its own. In the FT’s barcode, for example, the numbers 770307 are encoded using versions A, B, B, A, B and A of those digits, a sequence that tells the scanner that the left-hand digit is a 9. The one-dimensional UPC or EAN-13 remains the most widespread, though companies such as UPS have developed barcode systems of their own. Encoding Each digit is represented by four alternating black and white bars. Each bar can vary in thickness between one and four units (a unit is the thinnest bar you can see), but each digit must always be seven units wide. For example, in the FT’s barcode, the final digit, 9, is represented by three black bars, one white, one black and two white. At the left and right ends of the whole code are “guard bars”, which are always three units wide and are encoded 101 – one black, one white, one black. The middle is marked with a five-unit series: white, black, white, black, white. Further explanations are given in the text below. Supplementary barcode If required, a company can add an extra two- or five-digit barcode. In the FT’s case, this denotes what week of the year it is. Guard bars The beginning and end of the barcode are marked by three bars, each one unit wide. These are encoded 101 – black, white, black. Product number Each product has its own unique number. In the FT’s case, the first three numbers, 977, show that the product is a periodical. The following seven, 0307176, identify it as the FT. These 10 numbers make up the title’s ISSN number, which in the UK is issued by the British Library. Other prefixes include 978 for books (ISBN numbers) and a series of codes (50 for the UK, 00 to 13 for the US and Canada, 84 for Spain etc) that show which country has issued the number. Middle bars Always encoded 01010. Price code The retailer’s equipment is programmed to convert this digit into the price of the product. Day code Monday = 1, Tuesday = 2 etc. This is the barcode for a Saturday paper. Checksum The final number acts as a check that the barcode has been scanned correctly. The digits in the barcode’s “odd” positions – first, third, fifth etc - are added together: 9 + 7 + 3 + 7 + 7 + 8 = 41 The digits in the “even” positions are added together and the total multiplied by 3: 7 + 0 + 0 + 1 + 6 + 6 = 20 20 x 3 = 60 The two totals are added together and the checksum is whatever number it takes to reach the next multiple of 10: 41 + 60 = 101 So the checksum is 9