1D Barcodes

explanation of a 1d barcode quiet zone, guard patterns, check digit

The first barcodes implemented worldwide were 1D (one-dimensional) barcodes. These linear codes only contain alphanumeric data. Each character in the code represents something different about the product and a database provides information on what each character means.

In most cases, 1D barcodes are read from left to right. The widths of the spaces and bars relate to a specific character in the barcode. A quiet zone or margin is the white space to the left and the right of the barcode; this helps the reader to locate the barcode. As a general rule, the margins should be at least seven to ten times the narrowest bar width in the barcode.

All the other bars in the code are based off a ratio of the narrow bar width. For example, 2:1, 3:1 and 2.5:1 are common ratios that describe the width of white spaces and black bars based on the starting point of the narrowest black bar. Some barcodes also have a guard pattern. The guard pattern is at the beginning and end of the barcode; this pattern tells the reader where the barcode starts and ends.

1D Barcode Symbologies

1D barcode symbologies

Common 1D barcodes include but are not limited to: the GS1; UPC (Universal Product Code), which is common in retail and consumer goods; EAN in the European Union; and Code 128, which can describe any ASCII 128 character and is commonly used in logistics. Most of these barcodes include a check digit as part of its standard. The check digit is used to verify that the code is complete and not damaged or otherwise missing information; it does this by performing a mathematical operation on the data within the code.

Other 1D codes, such as Code 39 (widely used by the military), POSTNET (used by the United States Postal Service®), Codabar, and Interleaved 2 of 5 offer optional check digits.

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