Barcode

A barcode is a method of representing data in a visual, machine-readable symbolic form. Initially, barcodes represented data by varying the widths, spacings and sizes of parallel lines, a format known as linear or one-dimensional (1D) barcodes. These can be scanned by optical scanners called barcode readers. Later, two-dimensional (2D) variants were developed, using rectangles, dots, hexagons and other patterns, known as matrix codes or 2D barcodes. Unlike linear barcodes, these do not use bars and are read by purpose-built 2D optical scanners. Both types can also be read by a digital camera connected to a computer, with software analyzing the image to decode the code; a smartphone with a built-in camera and specialized application software can function as such a reader.

The barcode was invented by Norman Joseph Woodland and Bernard Silver, patented in the US in 1952. The invention was based on Morse code, extended to thin and thick bars. It took over twenty years for the invention to become commercially successful. An early industrial use was the KarTrak ACI system, developed by General Telephone and Electronics for the Association of American Railroads in the late 1960s. This scheme used colored stripes on steel plates affixed to railroad rolling stock, encoding ownership, equipment type, and identification number. Plates were read by trackside scanners while cars moved past, but the project was abandoned after about ten years due to unreliability. Barcodes became commercially successful after adoption for supermarket checkout systems. The Uniform Grocery Product Code Council chose a barcode design developed by George Laurer in 1973, whose vertical bars printed better than earlier circular designs. The first successful system using barcodes was in the UK supermarket group Sainsbury's in 1972, using shelf-mounted barcodes developed by Plessey. In June 1974, a Marsh supermarket in Troy, Ohio used a scanner to scan the Universal Product Code (UPC) on a pack of Wrigley's chewing gum. QR codes, a specific 2D barcode type, rose in popularity in the second decade of the 2000s due to smartphone growth. Other technologies like RFID have made inroads, but the simplicity, universality, and low cost of barcodes have limited their role.