How do barcodes work, and where did they come from?

A barcode is a visual pattern that stands for data. A scanner shines light on it, measures what reflects back, and turns the pattern into a string of digits or characters, which a computer then matches to a database record. The idea began in 1948 with two Drexel graduate students, and the rectangular Universal Product Code used on groceries was developed at IBM in the early 1970s. [1] [2] [3]

Linear (1D) barcodes use a single row of bars whose widths and spacings carry the data. Two-dimensional codes, such as QR codes, use a matrix of dots and boxes and hold much more data in a smaller area. According to IEEE, scanners work in one of two ways: a laser sweeps across the symbol and the scanner measures reflected intensity, or a camera-like sensor photographs the symbol and software decodes it. Image-based scanners have become dominant because they read both 1D and 2D symbols, tolerate tilt and rotation, and work from greater distances. [1] [4]

Contrast matters because the scanner depends on light reflecting differently from the pattern and from the background. This is why barcodes are usually printed in black on white, and why a low-contrast print raises the risk of a misread. Once the code is read, the number is looked up in a computer database, so the barcode itself is mainly an identifier, and the details about the item are stored elsewhere. [4] [2]

The problem came from a supermarket manager who asked the dean of the Drexel Institute of Technology in Philadelphia for a way to speed up checkout and stocktaking. Graduate student Bernard Silver took it up in 1948 and enlisted Joseph Woodland. IBM's history says Woodland got his key idea at a beach, when drawing his fingers through sand made him realize that wide and narrow lines could represent data like the dots and dashes of Morse code. The pair arranged the lines as a bull's-eye of concentric circles so it could be read from any angle, and they received a patent on October 7, 1952. [3] [5]

The design was not practical at the time. IBM says it needed a 500-watt light and a special tube, and Silver and Woodland sold the patent for 15,000 US dollars. The NSF similarly notes that faster computing, reliable scanners and better materials did not yet exist. [3] [2]

By 1970 grocery executives agreed they needed a standard scannable symbol and formed a committee to seek proposals. IBM engineer George Laurer led its response. He judged that the bull's-eye was prone to smearing when printed, so he proposed a linear design instead, with 30 black and 29 blank vertical lines, readable by laser from any direction and small enough for most packages. IBM credits its success to the design, newly available laser technology, and enough market demand to justify the cost. [3]

IBM dates the UPC's official birth to April 1, 1973, while IEEE describes it as standardized in 1973. On June 26, 1974, a checkout employee at a Marsh supermarket in Troy, Ohio, scanned a pack of Wrigley's Juicy Fruit gum, the first grocery scan. Barcodes are now used in manufacturing, healthcare, logistics and identity documents, and billions are scanned daily. [3] [1] [6] [2]