At 8:01 am on 26 June 1974, at a Marsh supermarket in Troy, Ohio, a cashier scanned a 10-pack of Wrigley’s Juicy Fruit chewing gum. It was the first retail sale using the Universal Product Code (UPC) barcode.
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Inspired by Morse code
The idea goes back to 1948–52, when Norman Joseph Woodland and Bernard Silver patented a barcode. Woodland reportedly got the idea by drawing Morse code dots and dashes in beach sand and extending them downwards into thin and thick lines. Their first design was circular, like a bullseye.
Why stripes?
A scanner shines light across the code and measures how much bounces back. Black bars absorb light, white spaces reflect it, so the pattern of widths becomes a pattern of light pulses that a computer decodes into digits. Stripes can be read from any angle along the line, which is why supermarket scanners use crossing laser lines.
What the numbers mean
Most products you buy in India carry an EAN-13 code: 13 digits including a prefix for the country where the code was registered (India’s GS1 prefix is 890), a company number, an item number and a final check digit calculated from the others to catch scanning errors.
And then QR codes
QR codes, invented in 1994 by Denso Wave in Japan to track car parts, store far more data in two dimensions — which is why your UPI payment scanner uses them.
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