Convert String to "number"

Dear all,

 

i would like to convert a string character into a "number" to be able to compare 2 character to know which one is the first in the alphabetic order.

The best is to convert it into its ASCII code but i can't find how to do .
I know how to convert an ASCII into a char (Char::Construt(ASCII) ) but not the reverse.

Does this function exist? Or is there another solution?

 

Thanks by advanced