Barcodes allow machinery and computers to quickly scan information about an object, most commonly for inventory management purposes. The most famous use of barcodes is the Universal Product Code scheme used in retail stores, but barcodes are also used in warehouses, shipping, health care and manufacturing.
The first barcodes invented were one-dimensional barcodes consisting of vertical lines of varying thickness. By scanning a beam of light from a laser or LED over the barcode, a barcode scanner can determine what the numeric value of the barcode is from the reflected light. These barcodes are called one-dimensional as they are only read in one dimension along the width of the barcode. More recently, two-dimensional barcodes have come into wider use, partially due to the availability of software to easily scan these barcodes on computers and cell phones.
Barcodes were initially used industrially for managing railway stock in a system called KarTrak ACI. Invented in the 1960s, the KarTrak system placed barcodes on the sides of railway cars to identify the owner and cargo inside the car. Though the system was eventually abandoned, barcodes came into wide use in the 1970s with the advent of Universal Product Barcodes in grocery stores. These barcodes eventually spread to be used in retail stores of almost every kind.