To deal with some of the stuff Chris left you to think about, you might consider some of the functions available from the header
<cctype>. isalpha() for instance will be easier to use than checking that the integer value of the character is between 65 and 122, since there are a couple characters in there which aren't letters. isupper() or islower() can quickly tell you the casing of the letter as well (though you can come up with a solution where the case doesn't matter; I leave that as a challenge to you
)