Barcode Technology and Symbologies

A barcode is a machine-readable representation of data, encoded as a pattern that an optical scanner can decode quickly and with very few errors. The familiar form is the one-dimensional barcode, a row of parallel bars and spaces of varying width in which the relative widths represent digits or characters. Two-dimensional codes pack far more data into a compact area using stacked rows or matrix patterns. The specific rule set that defines how characters map to patterns is called a symbology, and many symbologies exist, each suited to particular uses.

Retail relies heavily on the EAN family (European Article Number, also known as the International Article Number), with EAN-13 and the shorter EAN-8 identifying consumer products; the related Bookland scheme encodes book identifiers, and supplemental codes add price or issue information. General-purpose symbologies include Code 128 and Code 93, which encode full alphanumeric data compactly, and Codabar, used in libraries and blood banks. Numeric-only codes such as Interleaved 2 of 5 and Discrete 2 of 5 are common in distribution and warehousing, while EAN/UCC 128 (now GS1-128) carries structured logistics data.

Postal services use dedicated symbologies, such as POSTNET (Postal Numeric Encoding Technique) and other height-modulated bar codes, to sort mail automatically. Two-dimensional symbologies such as PDF417 store hundreds of characters and include error-correction data, so a code can still be read even if it is partly damaged. Across all these schemes, the common principle is that an arrangement of light and dark elements, governed by a published symbology, encodes information that a reader translates back into characters.

Frequently asked questions

What is a barcode symbology?

A symbology is the encoding standard that defines how characters are represented as bars and spaces, including the widths, check digits and structure a scanner uses to decode the data.

What is the difference between EAN-13 and EAN-8?

Both are retail product codes in the EAN family. EAN-13 encodes thirteen digits for general products, while the shorter EAN-8 is used on small packages where space is limited.

How does a 2D code like PDF417 store more data?

It stacks multiple rows of code instead of a single line, packing far more characters into a small area and adding error correction so the code remains readable when partly damaged.