A Brief History of Barcodes

The use of bar coding  has been growing dramatically over the last 15 years.   With the adoption of UPS as the standard for retail grocery stores in the late 70's, barcodes  have become an  a fast, easy and accurate data entry method.   The correct use of barcodes can decrease employee time required and increase an organization's efficiency. 

How do barcodes work?

Barcodes are alternating patterns of light and dark lines that encode   information.  When scanned, barcode symbols can be converted back into the original string of text.  Most bar codes consist of patterns of rectangles but some of the newer symbologies use other shapes.  Barcodes are part of the automatic ID industry and are sometimes referred to as "keyless data entry" because they can be used to encode and decode information automatically.   Barcodes can be scanned with little or no error under less than ideal conditions.  In some situations they can even be scanned automatically without human intervention.  This explanation will focus on creating and printing barcodes rather than the physics of scanners.   The scanners which read barcodes emit a red laser of a specific frequency.

Barcode density:

The number of data characters which can be represented in a linear unit of measure. Bar code density is often expressed in characters per inch.

Barcode printer:

A printer used to produce barcodes on labels, tags and other paper materials.  A bar code printer can be a simple dot-matrix report printer or a sophisticated, dedicated device that uses thermal printing technology.

Barcode scanner:

A bar code scanner reads bar codes.  Bar code scanners are generally classified as wands, hand-held, projection/vertical or in-counter scanners.

Barcode verifier:

Barcode verifiers are designed to measure and ensure traditional print quality.    Barcodes are normally analyzed for wide to narrow ratio, print contrast, bar growth or loss and quiet zones and formats.

Check digit:

A character whose represented value is used as a mathematical check to ensure accuracy. Commonly used in SKU numbers and bar codes.

What are the different kinds of bar codes?

The most common codes, called "symbologies", are Code39, Interleaved 2 of 5, and UPC. There is no one symbology that is "the right one" for an organization. Each one has different advantages and disadvantages, and the choice should be based on the details of the application. Any modern bar code scanner can automatically recognize and decode all the common symbologies.

Everyone is familiar with UPC. It is the common bar code used in retail trade. Its advantage is standardization, in a form that allows many organizations throughout the world to interpret the same data. UPC has numerous disadvantages that keep it from being applied in other uses. It can only record numbers, not letters. UPC and its variants, such as EAN, can only record certain lengths of numbers. It only uses space efficiently if you want to record the same length of data it wants to record.

The most common industrial bar code symbology is Code39. It is sometimes called Code 3 of 9, because each character is represented by 9 bars, of which 3 are wide and 6 are narrow. A Code39 bar code can represent a mixture of letters and numbers, and even some special characters. There is enough redundancy in each character to make scanning accurate and fast. For additional reliability, a check digit can be added in some applications, to be verified by the scanner. Code39 is not very efficient in use of space. A typical density is 6 characters per inch. Higher densities are possible, but are more demanding of both the printing and the scanning equipment. A Code39 bar code can be any length, limited only by the available space.