MODULUS 11

• Each digit position of the basic number is assigned a weighted checking factor . The following factors are assigned, starting with the units digit and progressing toward the high-order digit:

  2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 . . .

• Each digit in the basic number is multiplied by its checking factor.

• The products are summed and then divided by 11. The remainder is subtracted from 11. The result is the check digit.

Example

If a check digit is generated using modulus 11 calculations and the result is 10, the check digit cannot be used and an error is returned. Modulus 11 check digits are the remainder from dividing the product of the calculations by 11 (see example above). Thus, if check digits are being generated for a continuous series of numbers, every eleventh number must be skipped to avoid this error.

If the product generated through the modulus 11 calculations is evenly divisible by 11 (no remainder), the resulting check digit is 11. In this case, the digit 0 is appended to the basic number.

To summarize, if the calculated check digit is 10, an error is returned; if the calculated check digit is 11, a zero is appended to the basic number.

When you attempt to add a modulus 11 check digit that evaluates to 10, the reformatter issues the message: "Check digit is invalid for modulus 11 calculation".

If ENTRY checks a field according to the FORMSPEC statement CDIGIT 11 and that field contains a value with a check digit that evaluates to 10, the same message is issued.