Check digits verify that the embedded barcode data is decoded correctly by the host system. The check digit is calculated from all the data characters in the barcode.
- Not all symbologies have a check digit - e.g. D2 of 5 doesn't
- Some symbologies give the option to include a check digit or not - e.g. Code 39
- In some symbologies the check digit is automatically embedded in the barcode - e.g. UPC A