Q:

How do I iterate through all possible combinations of this code? 

I need to be able to iterate through every possible ICD10 code (medical procedures).  The code is 7 characters long, with the first digit being 0-9, the second being 0-9 or B-Y, etc. 
I feel like this can be done best with recursion, but I can't seem to figure it out.  

A:

start with the last character, the ones place or what ever. 
add all the possibilities to an array. 
for each new colume add each possibilty to each item in the array and add all of these to a new array.  
repeat until have all...
you could make an enumerator form 0 - y

