A barcode is an optical, machine-readable representation of data Data usually describes something about the object that carries the barcode. Originally barcodes systematically represented data only by varying the widths and spacings of parallel lines and may be referred to as linear or one-dimensional (1D). Later two-dimensional (2D) codes were developed, using rectangles, dots, hexagons and other geometric patterns in two dimensions, usually called barcodes although they do not use bars as much. Barcodes were initially scanned by special optical scanners called barcode readers. Later application software became available for devices that could read images, such as smartphones with cameras.
An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads in the late 1960s. Developed by General Telephone and Electronics (GTE) and called KarTrak ACI (Automatic Car Identification), this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock. Two plates were used per car, one on each side, with the arrangement of the colored stripes encoding information such as ownership, type of equipment, and identification number. The plates were read by a trackside scanner then, for instance, located at the entrance to a classification yard while the car was moving past. The project was abandoned after about ten years because the system proved unreliable after long-term use.
Barcodes became commercially successful when they were used to automate supermarket checkout systems, a task for which they have become almost universal. Their use has spread to many other tasks that are generically referred to as automatic identification and data capture (AIDC). The very first scanning of the now ubiquitous Universal Product Code (UPC) barcode was on a pack of Wrigley Company chewing gum in June 1974.
Other systems have made inroads in the AIDC market, but the simplicity, universality and low cost of barcodes has limited the role of these other systems until technologies such as radio frequency identification (RFID) became available after 2000.