It’s back to school season, so here’s a short primer in Technology 101.

The story starts in 1948, when some engineering students at Drexel named Bernard Silver and Norman Woodland overheard their dean talking to the president of a local retail chain. He was hoping that somebody could create a better way to inventory all the products in his stores. The kids kicked some ideas around. Shortly thereafter, Woodland was sitting at home in Florida on the beach, and he drew some Morse code in the sand, and then expanded the dots and dashes upwards and downwards, creating a pattern of thin and fat lines separated by spaces. He realized that if he reproduced these lines on paper, and used a bright light to scan across them, he would essentially be creating the inverse of an optical movie soundtrack (wherein a stationary light has alternating-sized lines passed over it to transmit musical data). Flickering Lines = Coded Data. Hmmm.

Silver and Woodland refined the idea and realized that if they created these alternating lines in concentric circles, rather than straight parallel lines, data could be scanned off them in any direction. In 1952, the students applied for and received a patent for both the linear and circular data patterns, and for the equipment needed to decode them. They tried to sell it to IBM, but IBM felt the technology was too far ahead of its time. So the students sold the patent to local electronics manufacturer Philco, who in turn later sold the patent to RCA.

Meanwhile, a third graduate student from MIT named David Collins had spent his summers working for the Pennsylvania Railroad. After graduating, he joined GTE Sylvania and developed a system called KarTrak which affixed yellow and blue reflective stripes to every car in their rail system, that were scanned as they rolled by various checkpoints, and updated their location. KarTrak was adopted by the Association of American Railroads, and became the national standard.

It was later phased out, but by then the U.S. Postal Service was testing a similar system to mark and track all their trucks. And then the world of retail got involved, when the Kal Kan pet food company raised their hand and asked if anyone could help them more efficiently label and track their products.

In 1970, the National Association of Food Chains, working with McKinsey, developed an 11-digit coding paradigm for every grocery product, and challenged the big technology companies to develop a universal “bar code” labeling system. The winner? The bulls eye pattern that Silver and Woodward had sold to RCA. This solution went into an 18-month test in a Kroger’s store in Cincinnati. But, in a case of the analog taking down the digital, the printing of the circular labels often resulted in smears that rendered them unreadable. So, IBM came up with a simplified version more like Woodland’s original beach concept, using straight lines that was easier to print and handle, and it tested successfully.

It all came down to June 26, 1974, in a Marsh’s Supermarket in Troy, Michigan. Mr. Clyde Dawson pulled a pack of Juicy Fruit out of his grocery basket and handed it to Ms. Sharon Buchanan, who was working the checkout. She scanned it at 8:01 AM, and successfully completed the world’s first transaction by Universal Product Code, or UPC.

And so now, as your kids head back to college, you might be looking at your credit card statement and wondering, “How do these kids buy so much stuff so fast?”

Now you know which students to blame.