1974: A supermarket cashier scans a multipack of chewing gum across a bar-code scanner in Troy, Ohio. It's the first product ever checked out by Universal Product Code.

Some readers may be unable to remember when grocery clerks had to put price stickers on nearly every item in the store. And retail cashiers had to read a price tag by eye and key in the price by hand. But that's the way things were. The process was not only laborious, but it left the store manager with no idea of how much of each of thousands of different products had been sold and how much remained in stock.

There were four main methods of keeping tabs of inventory: Look for empty spots on the shelves and in storerooms, conduct a labor-intensive inventory during overnight downtime every week or so, take whatever the chain-store regional managers wanted to send you, or just guess. Good guessers at the local level got promoted to make regional guesses.

Even so, the supermarket bar code was a long time coming. It was an idea that needed to find a practical technology as well as appropriate application for it.

Drexel University graduate students Bernard Silver and Norman Joseph Woodland began working in 1948 on a retail-checkout system that would keep track of inventory. They started with ink patterns that would glow in ultraviolet light. Expensive. Hard to make the ink long-lasting.

Woodland left Philadelphia to work on the problem at his grandfather's apartment in Florida. He thought Morse code would be a good way to mark inventory, but optical readers would require the checker to line up the code at a specific angle. Not practical.

While on the beach one day, Woodland punched some dots and dashes into the sand, then idly lengthened them into vertical lines and bars. Voilà! Those elongated marks would be readable from nearly any angle.

Woodland and Silver coupled this with an idea from movie technology: Lee de Forest's 1920s sound-on-film system. They used light from a very hot 500-watt bulb to reflect off the printed lines and create patterns that could be read by a photomultiplier tube.

It worked, but it was too big, it was too hot, computers were still enormous and expensive, and lasers hadn't been invented yet. The duo tweaked the tech, using bull's-eye patterns instead of lines, for better readability. And they patented it. IBM was interested, but didn't offer the inventors enough money. They eventually sold the patent to Philco, which later sold it to RCA.

Sylvania came up with a system of color bars in the 1960s and '70s to mark railroad freight cars, but it didn't work well. Meanwhile, a company called Computer Identics started building an industrial bar-code system for factories, but it could only handle two-digit numbers.

RCA, using the Woodland-Silver patent, tested a bull's-eye code reader in 1972-73. The big problem was the ink smearing in the direction the printing press had run. Smears made those circles hard to read. With a bar code, you just had to set up the press to run in the direction of the lines, so they wouldn't smear side-to-side.

For that and other reasons, the RCA system lost out to an IBM laser-reader system when the supermarket industry settled on standards in 1973. After much testing, the first commercial location in Troy, Ohio, was selected because it was near Dayton, home of NCR, which designed the checkout counter.

So, at 8:01 that fateful June morning, shopper Clyde Dawson grabbed a 10-pack (50 sticks) of Wrigley's Juicy Fruit gum from his shopping cart at the Marsh supermarket, and cashier Sharon Buchanan made the first UPC scan. The cash register rang up 67 cents (three bucks in today's money). Retail history was made. The pack of gum itself is now displayed at the Smithsonian Institution's National Museum of American History.

The entire check-out counter cost $10,000 ($44,000 today). The scanner itself cost $4,000 ($17,600 today). Scanners from the same company now cost just 1 percent of that (a trifling quarter-percent when adjusted for inflation).

The initial high costs weren't recovered as quickly as promoters of the system predicted. But a network effect eventually took hold: The more products that had UPC codes, the more labor and consumer time was saved. And the more stores used the system, the lower the cost of the hardware, encouraging more stores to sign on, and so forth.

Today, retailers use the UPC codes not only to look up prices and control inventory, but to track individual consumer preferences, by credit card number or discount-club membership. The checkout computer can spit out coupons for products it thinks you might buy, and sellers can tailor their commercial pitches and strategize future marketing campaigns.

Besides the UPC code for retail goods, bar codes are now used all over the place: Rental-car companies put them on bumpers to track their fleets, airlines track luggage, shippers track packages, researchers track animals, NASA monitors heat tiles on its shuttle fleet, and fashion houses stamp bar codes on their models to make sure the right model wears the right parts of the right outfit at the right time in the fashion show.

A far cry from drawing lines in the sand.

Source: "Barcodes Sweep the World," by Tony Seideman; other sites