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Fixed algorithm for check digits.
The check digit is an industry-standard algorithm, the one used for UPC codes. To calculate the check digit of a 3DS console, separate the non-check digits into "odd" and "even" groups, where the "odd" group is digits in odd-numbered positions, and the "even" group is digits in even-numbered positions. (The first digit is "odd", with "first" representing "1".)
The check digit is an industry-standard algorithm, the one used for UPC codes. To calculate the check digit of a 3DS console, separate the non-check digits into "odd" and "even" groups, where the "odd" group is digits in odd-numbered positions, and the "even" group is digits in even-numbered positions. (The first digit is "odd", with "first" representing "1".)
After separating the digits, add the digits in each group together. Multiply the sum of the odd digits by 3, then add the sum of the even digits. Take this final sum modulo 10, and the result is the check digit.
After separating the digits, add the digits in each group together. Multiply the sum of the even digits by 3, then add the sum of the odd digits. Subtract this value from 100. Take this final value modulo 10, and the result is the check digit.
Example: CW404567772
Example: CW404567772
Evens: 0 + 5 + 7 + 7 = 19
Evens: 0 + 5 + 7 + 7 = 19
Applying the algorithm, we get ((3 * 21) + 19) % 10 = 2, matching the example's check digit.
Applying the algorithm, we get (100 - ((3 * 19) + 21)) % 10 = 2, matching the example's check digit.
The letter prefixes are a letter specifying the device, followed by one letter specifying the region in which it was sold. In some regions, a third letter is present; a current guess is that this letter distinguishes among factories for a given sales region. Note that several different sales regions' console may be considered to be the same region for region-locking purposes, such as Europe and Australia.
The letter prefixes are a letter specifying the device, followed by one letter specifying the region in which it was sold. In some regions, a third letter is present; a current guess is that this letter distinguishes among factories for a given sales region. Note that several different sales regions' console may be considered to be the same region for region-locking purposes, such as Europe and Australia.