bar code, computer coding system that uses a printed pattern of lines or bars to identify products, mail and packages, customer accounts, and the like. Bar codes are read by optically scanning the printed pattern and using a computer program to decode the pattern. In a linear bar code system, the code itself contains no information about the item to which it is assigned but represents a string of identifying numbers or letters. When the code is read by an optical scanner linked to a computer, the computer can provide and record information about the item, such as its price or the quantity sold, from and to databases.

The original North American Universal Product Code (UPC), which dates to 1971, used a set of two dark (usually black) and two light (usually white) bars of specified thicknesses to represent 12 numbers, but beginning in 2005 the Uniform Code Council, now known as GS1 US, adopted the similar European Article Numbering Code (EAN), which encodes 13 numbers and had become the international standard. The standards for the international product bar code system are managed by GS1, formerly known as EAN International, which is based in Brussels. The dark bars may be from one to three units wide and the light bars from one to four units. For registration purposes two one-unit dark bars are placed at each end and in the middle. Each item is assigned a unique numeric code, which is printed as a bar code on the item's packaging.

So-called two-dimensional (2D) bar codes permit the encoding of information about an item in addition to an identifying code. In a 2D bar code, two axes, or directions, are used for recording and reading the codes and the bar size is reduced, increasing the space available for data in the way that a column of words improves on a column of letters. Some 2D codes do not use bars at all, such as the United Parcel Service's hexagon-based Maxicode.

bar code

Printed series of parallel bars of varying width used for entering data into a computer system, typically for identifying the object on which the code appears. The width and spacing of the bars represent binary information that can be read by an optical (laser) scanner that is part of a computer system. The coding is used in many different areas of manufacturing and marketing, including inventory control and tracking systems. The bar codes printed on supermarket and other retail merchandise are those of the Universal Product Code (UPC).

bar code

The printed code used for recognition by a bar code scanner (reader). Traditional one-dimensional bar codes use the bar's width to encode just a product or account number. Two-dimensional bar codes, such as PDF417, MaxiCode and DataMatrix, are scanned horizontally and vertically and hold considerably more data. PDF417 is widely used for general purposes. MaxiCode is used for high-speed sortation, and DataMatrix is used for marking small parts. See bar code scanner, UPC, point of sale, AIM and PDF417. Contrast with RFID.

One-Dimensional Bar Code
This 1-D bar code is widely used as the universal product code (UPC) on millions of consumer items.

PDF417
This 2D PDF417 bar code image developed by Symbol Technologies contains the entire Gettysburg address. It is identified by patterns of vertical lines on each side. (Image courtesy of Symbol Technologies, Inc.)

DataMatrix
The DataMatrix code is used to mark small parts. It is identified by two solid lines and two alternating dark and light lines on its perimeter. (Image courtesy of AIM, Warrendale, PA, www.aimglobal.org)

MaxiCode
The MaxiCode uses hexagonal symbols and is identified by a bulls eye in the center. It is used for high-speed sortation. (Image courtesy of AIM, Warrendale, PA, www.aimglobal.org)

bar code

Commerce a machine-readable arrangement of numbers and parallel lines of different widths printed on a package, which can be electronically scanned at a checkout to register the price of the goods and to activate computer stock-checking and reordering

(convention)

bar code - A printed horizontal strip of vertical bars of varying widths, groups of which represent decimal digits and are used for identifying commercial products or parts. Bar codes are read by a bar code reader and the code interpreted either through software or a hardware decoder.

All products sold in open trade are numbered and bar-coded to a worldwide standard, which was introduced in the US in 1973 and to the rest of the world in 1977. The Uniform Code Council in the US, along with the international article numbering authority, EAN International, allocate blocks of unique 12 or 13-digit numbers to member companies through a national numbering authority. In Britain this is the Article Number Association. Most companies are allocated 100,000 numbers that they can use to identify any of their products, services or locations.

Each code typically contains a leading "quiet" zone, start character, data character, optional check digit, stop character and a trailing quiet zone. The check digit is used to verify that the number has been scanned correctly. The quiet zone could be white, red or yellow if viewed by a red scanner. Bar code readers usually use visible red light with a wavelength between 632.8 and 680 nanometres.