On this day in 1974, the first Universal Product Code was scanned at a supermarket cash register. The UPC bar code system was originally invented specifically for grocery stores, to speed check-out and help them keep better track of their inventory, but it proved so successful that it spread quickly to other retailers. The first patent for a bar code went to N. Joseph Woodland and Bernard Silver in 1952. Silver, a graduate student at Drexel Institute of Technology, overheard the president of the local food chain, Food Fair, asking one of the deans to research a system to automatically read product information during checkout. He told his friend Woodland and they began work on the idea. The first system used ultraviolet ink, which was expensive and faded quickly. Convinced that the system was workable with further development, Woodland left Drexel, moved into his father's apartment in Florida, and continued working on the system. His next inspiration came from Morse code, and he...