1. The letter after the check character would have a weighting of nine. 2. The remainder ( modulus 23 ) indicate the check character position in the alphabet. 3. Since January 2013, the format uses a letter after the current check character . 4. The letter value would be assigned the same as the check character 's. 5. Every symbol includes two check characters . 6. Finally, the resulting check code-point is mapped back to obtain its corresponding check character . 7. The sixth and last character of the CODEN is an alphanumeric check character calculated from the preceding letters. 8. The check character is calculated using a weighted addition of all the numbers and modulus calculation ( known as Modulus 23 ). 9. A normal block ending character ( ETB or ETX ) is followed by a check sum ( block check character or BCC ). 10. To generate the check character , start with the last character in the string and move left doubling every other code-point.
