Every beep at a supermarket checkout can be traced back to a conversation overheard in 1948.

Samuel Friedland, president of Philadelphia’s Food Fair grocery chain, had approached the Drexel Institute of Technology with a problem. He wanted a machine that could identify products automatically, speed up checkout and keep track of inventory.

Drexel declined the project. Graduate student Bernard Silver heard the conversation, however, and carried the problem to his friend Norman Joseph Woodland.

While thinking about it on Miami Beach, Woodland turned to the only machine-readable system he knew: Morse code. He drew dots and dashes in the sand, then pulled his fingers downward. The dots became narrow lines and the dashes became wide ones.

Morse code had become a barcode.

Woodland and Silver applied for a patent in 1949. Their preferred version was circular, with concentric rings that could be scanned from any angle. It resembled a bull’s-eye more than the pattern found on a cereal box today.

The familiar rectangular barcode came later. Its black bars absorb light while the pale spaces reflect it. A scanner measures the alternating reflections and translates the widths of both bars and spaces into numbers. The white background is therefore part of the code. The apparently empty areas are doing half the work.

A supermarket barcode usually contains neither the product’s name nor its price. It carries an identification number. The store’s computer uses that number to find the description, price and other information in its database.

The idea arrived decades before the machinery and cooperation it required. Supermarkets needed affordable computers and reliable laser scanners. Manufacturers needed to print codes accurately, and thousands of companies had to agree on a single standard.

The grocery industry adopted the Universal Product Code in 1973. On June 26, 1974, a cashier at a Marsh supermarket in Troy, Ohio, scanned a package of Wrigley’s Juicy Fruit gum. Twenty-six years had passed since Food Fair first posed the problem.

Designing the stripes took ingenuity. Getting an entire industry to agree on the same stripes took much longer.

In 1994, engineers at the Japanese company Denso Wave developed the QR code to track automobile parts. A conventional UPC records information in one direction, across its bars and spaces. 

A QR code stores information both horizontally and vertically in a grid of small squares, giving it room for far more data.

The three large squares in its corners help a camera locate and orient the pattern. Built-in error correction can preserve the information when part of the code is scratched, stained or missing. A QR code can also contain text or a web address rather than merely directing a store computer to a product record.

The barcode gave products machine-readable names. The QR code gave the pattern enough room for a message.