What is a Barcode Symbology?
A barcode symbology is merely the language or encoding the barcode uses. It’s the methodology used to change the characters of what you want to encode into the black and white lines in the barcode itself. Just as the printer needs to know the language or encoding of the particular type of barcode it is printing, the barcode scanner needs to be able to understand or “decode” the language of the encoded label to change it into characters you could type on a keyboard.
Before we start listing each of the most common barcode symbologies, here are a few terms you need to be familiar with:
- Character Set:
This is the set of characters which can be encoded in the barcode. The character set may be numeric only, alpha-numeric, or may include control characters. Understanding the character set allowed by the barcode symbology is critical in choosing whether the particular symbology is appropriate for your application.
This refers to the number of data characters per inch of barcode or width of the barcode. The width of the barcode is influenced by the following 3 variables:
- Symbology of the barcode: Different barcode symbologies have different widths. Some are more compact than others. Some combine characters in a single pattern of bars and spaces, others have a single pattern for each character. With the other variables the same, here’s an example how the choice of barcode symbology affects the barcode width:
- Ratio of Wide to Narrow Elements: Basically, changing the width of the narrowest bar in relation to the width of the thickest bar. Ratio is important when making sure that the barcode scanner you’ve selected can read the codes you’ve printed.
- Width of the Narrowest Bar (also known as x-dimension): The most common user variable density component, the width of the narrowest bar is measured in thousandths of an inch or mils. The standard density of common barcodes is usually represented as 7 to 12 mils. Very high density barcodes (like those on circuit boards, cell phones and other electronic equipment can have a density as low as 3 mils. This density variable is referred to in all manufacturer data sheets when documenting scanner performance on various codes.
- 1-Dimensional or Linear Barcode Symbology: Barcodes with vertical bars that typify the common understanding of what a barcode looks like. The bars are vertical to the substrate the code is printed on. In a linear or 1-dimensional barcode symbology, data is encoded in a horizontal line like a word we would write on a paper
- 2-Dimensional Barcodes: A 2-Dimensional barcode symbology allows the storage of data in both the x and y coordinates of the barcode. This barcode symbology must be read in entirety from side to side and top to bottom in order for the barcode scanner to decode its contents. It can appear as a square with smaller squares or hexagons printed inside it, or like a lot of little linear barcodes cut and stacked on one another (PDF417).
Most Common Barcode Symbologies
There are a variety of different barcode symbologies, each of which evolved as a standard within a certain industry or across industries to solve a particular problem. Let’s take a look at the more common ones:
UPC/EAN Barcode Symbology
This is the barcode you find on food and products in stores. UPC barcodes are of fixed length, and printing standards are tightly controlled by the Universal Products Commission. The UPC code is not used anywhere else but in the retail industry. This symbology was first developed to meet the needs of grocery retailing.
CODE 39 Barcode Symbology
Developed because some industries needed to encode the alphabet as well as numbers into a barcode, Code 39 is by far the most popular barcode symbology for applications not in the retail industry. It is typically the non-food standard barcode, and is used for ID, inventory, and tracking purposes in various industries such as manufacturing and warehousing. Because each character encoded has its own series of bars and spaces and because it used a “*” for a start and stop character, Code 39 isn’t the most dense barcode symbology.
CODE 128 Barcode Symbology
The Code 128 symbology is a more compact code than the Code 39 barcode, and it encodes a larger selection of characters. Code 128 is very compact, and is often used in the shipping and electronics industry.
Interleaved 2 of 5 Barcode Symbology
Another popular symbology in the shipping and warehousing industry, Interleaved 2 of 5 compact symbology relative to the Code 39. You’ll see them on ground shipping boxes from the major shipping companies.
Postnet Barcode Symbology
The Postnet symbology was developed for the US Postal Service specifically for encoding zip codes for machine routing of letters and packages. Note that this code is “Height-Modulated”. The spaces between the bars and the bars themselves are the same width. The characters are represented by the height of the bars.
PDF417 Barcode Symbology
Know as a 2D (two-dimensional) barcode, this is a high density, non-linear symbology that looks like a lot of little linear barcode cut up and stacked on top of one another. But the advantage of PDF417 over the other barcode symbologies listed above is that PDF417 is really a portable data file (PDF) as opposed to simply being a reference number. Some states require a 2D barcode be printed on your driver’s license. If your state has this requirement, it’s interesting to know that there’s room enough in this barcode to encode your name, photo and summary of your driving record, and other pertinent information. As a matter of fact, a PDF417 barcode can encode the Gettysburg Address in a space the size of a postage stamp.
DataMatrix Barcode Symbology
A true 2-Dimensional barcode symbology, the Data Matrix barcode symbology is becoming popular on printed media, and in industrial applications where the amount of space available is small in relation to the amount of data that must be encoded. In the latter application, the barcode is inked or engraved directly on the part to assure its longevity. Reading barcodes etched directly on the parts is commonly referred to as DPM reading.