The mapping between messages and barcodes is called a symbology. The specification of a symbology includes the encoding of single digits/characters of the message as well as the start and stop markers into bars and space, the size of the quiet zone required to be before and after the barcode as well as the computation of a checksum.
Linear symbologies can be classified mainly by two properties:
Continuous vs. discrete
Two-width vs. many-width
Some symbologies use interleaving. The first character is encoded using black bars of varying width. The second character is then encoded by varying the width of the white spaces between these bars. Thus characters are encoded in pairs over the same section of the barcode. Interleaved 2 of 5 is an example of this.
Stacked symbologies repeat a given linear symbology vertically.
The most common among the many 2D symbologies are matrix codes, which feature square or dot-shaped modules arranged on a grid pattern. 2D symbologies also come in circular and other patterns and may employ steganography, hiding modules within an image (for example, DataGlyphs).
Linear symbologies are optimized for laser scanners, which sweep a light beam across the barcode in a straight line, reading a slice of the barcode light-dark patterns. Stacked symbologies are also optimized for laser scanning, with the laser making multiple passes across the barcode.
In the 1990s development of charge coupled device (CCD) imagers to read barcodes was pioneered by Welch Allyn. Imaging does not require moving parts, as a laser scanner does. In 2007, linear imaging had begun to supplant laser scanning as the preferred scan engine for its performance and durability.
2D symbologies cannot be read by a laser, as there is typically no sweep pattern that can encompass the entire symbol. They must be scanned by an image-based scanner employing a CCD or other digital camera sensor technology.
Different regions of the world – and different types of products – use their own unique barcode formats. Here's a rundown on the various types of barcodes you'll find around the world and on our site.
Description: The Universal Product Code is the standard format of barcode symbology in the United States, Canada, the United Kingdom, Australia, New Zealand, and many other countries around the world. It consists of 12 digits along with vertical stripes, or "bars", which are easy to read by an optical scanner. A UPC is divided into "left"and "right" sections, with six digits in each section.
Barcode formats: UPC-A symbols consist of 11 data digits and one check digit – 12 digits in total. The first digit is a number system digit, which typically represents the product type; the next five digits are a manufacturer code; and the final five digits are the specific product's identifier. UPC-E is a shorter UPC code, consisting of seven digits, which is usually used for small retail items.
Description: This barcode type's acronym comes from its original name of "European Article Number." It looks extremely similar to a UPC-A, with 12 vertical bars divided into "left"and "right" sections. It also includes a 13th digit out to the left, which is known as a "check digit".
Barcode formats: EAN13 is a 13-digit barcode, used to mark packages with an item number. EAN8 is a shorter, eight-digit code, used to mark small packages. Both types of EAN are mainly used outside North America.
Description: This type of barcode is used specifically to help retailers and libraries track books. Each new edition and variation of a book gets its very own ISBN.
Barcode formats: ISBN-10 is a 10-digit barcode for books printed before 2007. In an ISBN-10, the first two digits specify the book's group; the next five digits specify the publisher; the three digits after that specify the book's title. The final character of an ISBN-10 is known as a check digit. ISBN-13 is a 13-digit barcode for books printed on or after January 1, 2007. ISBN-13 digits serve largely the same functions as those of an ISBN-10, except that they're now also preceded by a three-digit Global Standards (GS1) number.