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Linear Barcodes

A linear barcode is a collection of bars and spaces that define a set of numbers or letters. There a many different linear barcodes (or symbologies) but luckily there are only a few that are used most of the time. This small number of symbologies has been standardized by ISO and thus there is a standardized definition of what the bars and spaces mean.

Some symbologies use a fixed length definition to ensure that the same number of bars and spaces are shown to the scanner each time. Others use special characters to define what data is encoded and so can allow variable length symbols to be generated.

Each barcode was probably designed with a special purpose in mind when the inventor created the code. This symbology has thus been optimized to produce the best symbol for the type of application where it is used. Examples of linear symbologies are:

EAN/UPC. This symbology comes in a variety of different formats from an 8 number version to a full 14 number version of the number used to identify goods in the retail store.

Code 128 is a full alphanumeric barcode that allows the user to encode symbols as long as needed giving a very efficient symbol size.

Code 39 is an alphanumeric symbology, which like Code 128 can be as long as needed. It was originally designed to encode only the uppercase letters, the ten digits and some special characters, however, the full ASCII character set can be encoded by using a two character encoding.

Interleaved 2 of 5 (ITF or I 2/5) is an all numeric code. It can be as long as is needed, as is relatively high density.

There are many other linear barcodes that are used.