Barcode Symbology

Posted by Tom Graham on

To understand ADC technology you have to understand what symbology is. Symbology is a method of representing data characters using barcodes. We distinguish different types of symbologies and each symbology has a unique way of encoding data characters. To read barcodes we use scanners. Two main symbology types are 1D and 2D.

1D Barcode Symbology Example

Code 3 of 9

  • Each data character is represented by 9 elements - wide (W) and narrow (N) bars and spaces
  • 3 out of 9 characters must be wide

Code 3 of 9


2D Barcode Symbology Example


PDF417 is 2D symbology is where data is encoded into “Codewords.” Codewords are a group of bars and spaces representing one or more numbers, letters, or other symbols. The codewords are represented by patterns of dark (bar) and light (space) regions. Each of these patterns contains four bars and four spaces (where the 4 in the name comes from). The total width is 17 times the width of the narrowest allowed vertical bar (the X dimension); this is where the 17 in the name comes from. Each pattern starts with a bar and ends with a space. Of the 929 available codewords, 900 are used for data, and 29 for special functions.


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