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What do the dashes and dots on barcodes really mean?

You see them all over the place, from cereal boxes to prescription labels, from envelopes to electronics – barcodes are everywhere. But what do those little black lines and dots mean? Barcodes themselves do not contain descriptive information, rather they provide a reference which is scanned and looked up in a database that does contain the descriptive information such as item name, price and quantity. Alternatively a URL does not contain the descriptive information in the website it references.

There are two major types of barcodes – one and two dimensional. One dimensional (1D) are probably more commonly seen, they are on every item you see in the store. 1D barcodes are made of a series of vertical lines (bars) and spaces of varying widths. These bar and space combinations are strung together to represent different characters. Two dimensional codes use a series of dots, blocks and other geometric shapes into a square or rectangular pattern. 2D barcodes are generally able to contain much more information than 1D. Where a 1D barcode such as a UPC code contains 12 digits, a 2D barcode such as a QR code may contain thousands of alpha-numeric characters.

In either case the codes need to be read by something – a reader. Barcode readers act as a translator between the code itself and the data it contains (those 12 digits in the UPC for example). Today you can download literally dozens of apps for your smartphone that will read both 1D and 2D barcodes, but here’s the trick; there are literally dozens of different “languages” of barcodes to translate. Let’s take a look at some of the more commonly used codes.

clip_image002 Universal Product Code (UPC) has been standardized worldwide for retail and food sales. It is the code seen on virtually every product you buy at the store. It uses 12 digits (number only) represented by bars and spaces of four different widths. UPC is a subset of the International Article Number system which includes an additional check digit.

clip_image003 Code 39 is used primarily for inventory and manufacturing applications. Each character comprises nine bars and spaces, of which three (either bars or spaces) are wide and the remaining nine are narrow. Code 39 supports 43 characters: 0-9 A-Z and several special characters. There is no predefined limit to the length of code 39 barcodes, sometimes leading to long codes unsuitable for smaller items.
clip_image005 Code 128 is used in shipping and packaging industries. Where code 39 lacks, Code 128 excels – it is the most compact barcode. It uses all 128 ASCII characters and includes a check digit. Other 1D barcodes include codes standardized for pharmacy companies as well as the various postal codes.
clip_image007 PDF417 barcodes are used across multiple industries for its capacity to store large amounts of data. It can encode things like fingerprints used on identification cards. It contains units of 4 bars and spaces and each pattern is 17 units long.
clip_image009 Aztec codes are a 2D code with a bull’s eye in the middle and are read in a spiraling direction. They are primarily used in European transportation applications.
clip_image011 Data Matrix codes are used in the aviation industry as well as the Department of Defense. They are used in cases where a linear barcode would be too long on small objects. They consist of a rectangular (usually square) block made of black and white squares. They can vary in size – generally from 8×8 to 144×144.
clip_image013 QR codes originated in the automotive parts industry in Japan. They have since been used extensively in advertising, entertainment and promotional applications, particularly aimed at smartphone users due to their ease of readability. QR codes can not only contain alphanumeric and bit/binary but also Kanji data as well.
clip_image015 High Capacity Color Barcode was developed by Microsoft using a series of colored triangles. Uses are similar to Data Matrix and QR code uses.

Barcode use has grown to universal proportions since they were first introduced around 40 years ago. Recognizing the different types and uses of these barcodes will help you in identifying not only which style will work for you but also the readers and applications to support them.