I still can't get this to work. I am obviously missing something. So what I want to do is: Use an input DNA sequence and put in array. For each element in array check if the element is a nucleotide. If not a nucleotide print "not a valid character at position xx". In the end, print out the number of characters that were valid and the number of characters that were not valid, calculate the percentage of non-valid characters. Does this make sense? Thanks