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Barcode Labels: Understanding the Code

Barcode Labels: Understanding the Code

What's in a Barcode Label?

Barcode labels were designed to be read by computers, not the human eye, but it is useful to understand how information is encoded in these familiar yet incomprehensible symbols. Different types of barcodes are used in different contexts and each has its own method of representing numeric and alphabetical data. However, the most common types share a general structure.

This diagram shows a typical barcode using the EAN-8 symbology, a European standard seen on many products.


Barcode Labels - Printing and Software - Understanding the Code

When printing the labels, numbers are set along the bottom to provide information about the product in what is often rather drily referred to as "human readable form". It is as obsolete as Sanskrit to devotees of barcode technology, but useful in the supermarket when the code on your can of beans won't scan and needs to be punched in by hand.

Barcode Labels Section by Section

The numbers along the top do not appear on actual barcode labels but represent the separate sections as identified by scanners and reader software. In each section a piece of data, in this case a number, has been encoded into a graphic pattern of lines. The height of the lines is irrelevant, except that very short lines would make reading more difficult. It is the width and frequency of the lines that tells a computer what number is represented. In this code each section has seven subdivisions which are either black or white strips. Represented as 0 for white and 1 for black, the number 5 is shown in section two as 0110001.

Sections two and three in this example are number system digits. Different number systems are used for different classes of products, so this is useful for getting closer to identifying the item.

Sections four, five, seven, eight and nine are all data digits. When printing barcode labels these provide the identifying information on the article. The number, here 12345, refers to data in a database which will in turn provide more information about that article, for example a price.

Accuracy of reading is essential to a barcode system, and for this reason all barcode labels have built-in ways of checking that they are being read correctly.

Sections one, six and 11 are called "guard bars". These tell the computer what part of the code is about to be encountered - the computer software will know what to expect, in whichever direction the barcode is read.

Section 10 provides a check digit. This is used to check that the numbers have been read without error. Often this number is the remainder after a series of calculations have been applied to the previous digits, and can only be one number if the label has been read correctly.

This is about as simple as it gets. Many barcode labels use much more complex systems of representing information and cram more of it into smaller and smaller spaces. The goal remains the same in every case, and that is to provide efficiently read, accurate data to computers in a wide range of situations.