Those little lines do so much …
1D: See Linear.
2D: Barcode symbols designed to increase data capacity beyond linear barcode symbols while still being readable by optical means. Two categories of two-dimensional symbols exist: multi-row (or stacked) and matrix. A 2D barcode can only be read be an imager, since a picture needs to be taken and then decoded. DataMatrix and Maxicode are examples.
Bar height: The height of the bars. The taller the bars, the easier it is for a person with a hand scanner to scan the barcode. Bearer bars: Some barcode symbologies are unsecure, meaning that if the barcode scan beam is partially off the barcode it may still result in a good read, although the data may be partial or incorrect. Bearer bars are bars at the top and bottom of the barcode bars that prevent partial reads. Code I 2 of 5 symbology contains bearer bars.
Bi-Directional: Characteristic of most barcode symbologies which permits scanning of the barcode symbol in either the left-to-right or right-to-left direction.
Check character: Extra digit added at the end of a barcode to allow the scanner to confirm that it read the barcode correctly. It is typically stripped from the data and not transmitted to the host.
Clear Area: See Quiet Zone.
Error Correction Level: Redundant data correction and/or extra error correction in some barcode symbologies, allowing for some of the barcode to be missing and still result in a correct scan.
Linear: A single line barcode. The UPC barcode is linear, as are Code 39, I 2 of 5, and Code 128.
Mil: A unit of measure equal to 1/1000 of one inch. For example, a line 1/4 inch wide would be 250 mils.
Narrow to Wide Ratio: The ratio of the narrowest bar (see “X dimension”) to the widest bar in a linear barcode symbol. Common values are 2, 2.5, and 3. Just like X dimension, a larger ratio generally means better readability by the barcode scanner.
Print contrast: The difference in reflectance between the bars and spaces of a barcode. Generally, the greater the contrast the easier it is for the reader to read the barcode, although some really reflective surfaces cause problems.
Quiet Zone: The minimum required space for barcode scannability, preceding the Start Character and following the Stop Character of a barcode symbol. The quiet zone should be free from any printing and be the same color and reflectance as the background of barcode symbol. The Quiet Zone should be ten times the width of the narrowest element in the barcode, or 0.25 inch minimum. Also known as Clear Area.
Stacked: A linear barcode that has been continued on the next line. Special commands are added so that the multiple rows are decoded in the same way a linear barcode would be. If you can drag a straight line through a symbol and hit all of the lines, it is stacked. PDF417 is technically a stacked symbology.
Start and Stop Characters: Special barcode characters that tell the scanner to start and stop reading a barcode symbol. The Start Character is typically found on the left side of a barcode symbol. The Stop Character is typically found on the right side of a barcode symbol. The characters signify to the scanner/reader that everything between them is data. Start and stop characters are usually stripped-off and not transmitted to the host. Compare to human readable text, where a capital letter indicates the beginning of a sentence and ending punctuation shows the end of the sentence.
Symbology: A defined method of representing numeric or alphabetic characters in a barcode; a type of barcode. Common symbologies include Code 39, Interleaved 2 of 5 (I 2 of 5), PDF417, Code 128, UPC and GTIN.
X-Dimension: The measure of the narrowest bar in a barcode, measured in thousandths of an inch. A 20 Mil barcode will have a narrow bar width of 20/1000 of an inch, or 0.0020”. Generally, the larger the mil value the easier the scanner can read it and from greater distances. Bar codes and scanners have different X dimensions so they must be matched. In addition to all of the variation within the barcodes themselves, there are also standards within industries. The automotive, electronics, and retail/distribution industries are just three of the many that have developed standardized label formats with specific barcodes and data structures so that all companies within that industry can read each other’s codes and use the data seamlessly. When developing a barcode system for use either in-house, with a vendor, or with a customer, it’s important to make sure that standardization is applied to ensure maximum usability. There are many additional sources of information on the Internet and in print, but the de facto standard is “The Bar Code Book”, by Roger C. Palmer, from Helmers Publishing.