A barcode (also bar code) is a visual, machine-readable representation of data. The data usually describes something about the object that carries the barcode.
Traditional one-dimensional barcodes systematically represent data by varying the widths and spacings of parallel lines. Later, two-dimensional variants as the QR Code were developed. They are using rectangles, dots, hexagons and other geometric patterns.
The use of barcode technology in an industrial setting can be traced back as far as the 1960s, with some early implementations to identify railroad cars. They were scanned by special optical scanners called barcode readers. Later application software became available for devices that could read images, such as smartphones with cameras.
Barcodes were commonly used in production processes, stock managements, or on grocery store shelves to automate the process of identifying items. More recent uses for smart phones include linking to web content, or even online payments.