Doris Number

The Doris Number is a unique alphanumeric code for parody media. This number identifies 1,000 parodies. The reason why Doris Number is required for parodies is to distinguish the movies from the others with the same name or to process sorting of parodies.

Structure
Doris Number appears in the structure L9999999L9, where the first and ninth characters are letters and the remaining are numbers. The first character must be between L and V (excluding O), and the ninth character must be between A and Z (excluding I and O). The first through ninth characters are random and the last digit is the check digit.

Check digit calculation
The check digit must be between 1 and 9 and is derived from the steps:
 * 1) Do a digit sum of the second through eighth digits. Call this variable A.
 * 2) Convert the first and ninth letters to numbers based in the position of the alphabet, where "A"=1 and "Z"=26. Multiply those by 2 and add it to A.
 * 3) The digit sum of A is executed until the result is one-digit. Call this last value X.
 * 4) Tenth digit = X.

Example
Baileywick of the Caribbean has the Doris Number U5602194W7. The calculation of check digit can be done as follows:
 * U 5602194 W7 = 5+6+0+2+1+9+4 = 27
 * U 5602194 W 7 = 27+(21×2)+(23×2) = 115
 * U5602194W 7 = 1+1+5 = 7 (the check digit)

More information

 * Doris Number on Spoof Wiki.