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Calculate Checksum digit for Code 128 C and GS1

I cannot seem to figure out how the last two digits of this barcode were calculated. There is another barcode very similar to the first one that I cannot figure out as well: 93131533329680002685.

Both barcode numbers are related to each other so I'm wondering if the machine or software that generated these barcode numbers uses their own encryption method for calculating the checksum digit.


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06-22-23     337 day(s) ago    

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Brant

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It sounds like you are referring to a GS1 barcode type; barcodes for this may be easily generated with the GS1-128 Font. If that is the case, you may be able to figure that out by referring to the GS1 General Specifications Standard or the GS1 AI Reference. The specification includes information about how the MOD10 check digit is calculated. The MOD 10 is a visible character because it is part of the GS1 system and the Code 128 Checksum is not visible because it is part of the barcode symbology. The checksum for Code 128 is not an encryption algorithm, it is a calculation. For more information about how the check digit is calculated refer to the Code 128 Check Character Calculation Examples. To automatically calculate the check digit in your environment, implement one of our Font Encoders with the appropriate barcode font.

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Other Answers (1)
I understand it is a Code 128 C barcode. Thank you for clarifying the checksum. I can calculate that number and check manually, phew. I am just finding out about barcodes as of very recently even though I haven’t thought about math in about a decade being an angsty teen back then I never went to college or did anything related to maths. But for whatever reason, barcodes piqued my interest a few days ago and it feels like it’ll haunt me in my dreams if I don’t satisfy the need to understand what it is I am trying to understand and I don’t even know.

Now I have read up so much about barcodes but am getting frustrated because I cannot seem to figure out how the last two digits that are presented in the human-readable text have come to be the digits that they are. For the barcodes I have here 93131533329670006129 and 93131533329680002685 the first 2 digits (93), or maybe even the first 4 (9313), I am assuming is the AI assigned to company internal information. The next 6 (131533) or 4 (1533) digits remain the same, not entirely sure what the numbers mean but I think they just display a controlled variable numeric value, a constant, maybe a GS1 Company Prefix? The existing structure only allows companies with a 6-digit prefix the ability to coupon. The new format can accommodate variable-length prefixes. But I don’t think this part of the barcodes matters too much. The next 5 digits (32967 and 32968) change and I believe they could be transaction numbers because I think these barcodes are indicative of coupons or vouchers.

Coupons typically encode a monetary value and the value codes can now be in any amount up to $999.99, and they are not limited to a table of only 100 or however the amount of possibilities there are. This points me to believe that the next string of 5 digits (00061 and 00026) are monetary values. The last 2 digits (29 and 85) after these values are where I am having trouble. I have no idea how these numbers came to be and what these numbers are.

Is it the check symbol character and the stop symbol character values?

Are these two digits the portion of the barcodes that have to do with the encryption algorithm to validate the barcodes separate from the checksum validation?

Can anyone point me in some direction or guess as to what these last two digits mean and how they came to be?

I am going through a barcode phase and I don’t know why.

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