A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally, barcodes represented data by varying the widths and spacing’s of parallel lines, and may be referred to as linear or 1 dimensional (1D). Later they evolved into rectangles, dots, hexagons and other geometric patterns in 2 dimensions (2D). Although 2D systems use a variety of symbols, they are generally referred to as barcodes as well.

The first use of barcodes was to label railroad cars, but they were not commercially successful until 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 Auto ID 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 the first decade of the 21st century over 40 years after the introduction of the commercial barcode.

Use --Barcodes such as the UPC have become a ubiquitous element of modern civilization.Some modern applications of barcodes include:

Barcodes are widely used in shop floor control applications software where employees can scan work orders and track the time spent on a job.

The tracking of item movement, including rental cars, airline luggage, nuclear waste, mail, express mail and parcels.

Some 2D barcodes embed a hyperlink to a web page. A capable cellphone might be used to read the barcode and browse the linked website, which can help a shopper find the best
price for an item in the vicinity.

In the 1970s and 1980s, software source code was occasionally encoded in a barcode and printed on paper.