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For instance, the UPC-A barcode for a box of tissues is "036000241457". The last digit is the check digit "7", and if the other numbers are correct then the check digit calculation must produce 7. Add the odd number digits: 0+6+0+2+1+5 = 14. Multiply the result by 3: 14 × 3 = 42. Add the even number digits: 3+0+0+4+4 = 11.
The check digit is computed as follows: Drop the check digit from the number (if it's already present). This leaves the payload. Start with the payload digits. Moving from right to left, double every second digit, starting from the last digit. If doubling a digit results in a value > 9, subtract 9 from it (or sum its digits).
Once you have calculated your check digit, simply map each character in the string to be encoded using the table above as a reference to get the binary map of the bar code; remember to precede the code with "start" and to end it with "stop" For example, to map the string 1234567 with a Mod 10 check digit it would produce the following binary map:
Assign the weights 8, 6, 4, 2, 3, 5, 9, 7 to the 8 digits, from left to right. Calculate S, the sum of each digit multiplied by its weight. For example, for the number 47312482: S = 4×8 + 7×6 + 3×4 + 1×2 + 2×3 + 4×5 + 8×9 + 2×7 = 200. Calculate the check digit C = 11 − (S mod 11). If C = 10, change to C = 0. If C = 11, change to C = 5.
The Luhn mod N algorithm is an extension to the Luhn algorithm (also known as mod 10 algorithm) that allows it to work with sequences of values in any even-numbered base. This can be useful when a check digit is required to validate an identification string composed of letters, a combination of letters and digits or any arbitrary set of N ...
Finally, the last digit is known as a “check” digit. This is based on a mathematical formula, and it confirms the validity of the card. Other numbers found on a credit card.
Because Codabar is self-checking, most standards do not define a check digit. [3] Some standards that use Codabar will define a check digit, but the algorithm is not universal. For purely numerical data, such as the library barcode pictured above, the Luhn algorithm is popular. [4] When all 16 symbols are possible, a simple modulo-16 checksum ...
In chemistry, the last digit of the CAS registry number (a unique identifying number for each chemical compound) is a check digit, which is calculated by taking the last digit of the first two parts of the CAS registry number times 1, the previous digit times 2, the previous digit times 3 etc., adding all these up and computing the sum modulo 10.