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 What is a Barcode?

You have probably seen those black and white bars on the food you buy at the grocery store – that’s a linear bacode.

The code used on the goods at the grocery store is an EAN or UPC symbol. This is a symbology with a defined set of rules as to how the bars and spaces should be interpreted as numbers. The world has agreed to use the same symbology and so manufacturers over the world know that they can put one barcode on the box of food and that every store that uses a barcode scanner will be able to read it.

The first time a barcode was used to identify a retail item was in June 1974. After much planning and work to provide a means to recognize an item from a barcode an system was installed at Marsh’s supermarket store in Troy, Ohio. A packet of chewing gum was the first item taken from the shopping basket and scanned and the system we use every day to buy our groceries (and many other items) all over the world was born.

A symbology is like a language, defining how the various black and white, bars and spaces, are put together. It defines the rules that used to encode the various characters, how to print them, and anything that is needed to check if there are errors in the decoding of the symbology.

Now EAN/UPC code is not the only symbology that is in use. In fact it is not the only type of barcode that exists. In the linear area (that is barcode symbologies that are a single row of bars and spaces) there are many different symbologies.

We also have something that we call a 2D symbology. This is a collection of “dots” that make up the “barcode” but they are not all in a row. The characters may be made from a matrix of dots or perhaps multiple rows of much smaller linear looking bars.

The advantage of the 2D codes are that they are smaller/ and/or contain much more data.. Because they are smaller they can be designed to include a means of error correcting if the scanner is unable to read the symbol correctly.

A familiar example of a 2D symbology is the one inch square symbol on a parcel shipped by UPS. This code is called a MaxiCode and it is defined in an ISO standard. Another example you may have seen is PDF417. This multi-row symbology is often used on boarding passes by the airlines or maybe on your driver’s license application form.

Of the many hundred symbologies that exists there are 12 of them that have been standardized by ISO and thus are the main ones that we use.