DAVID MALAN: Let's now refine this program a bit. Wouldn't it be nice if there were a function called, say, islower that could return true or false based on whether a given character is lowercase? Wouldn't it be even nicer if there were a function called toupper that could convert a lowercase letter to uppercase? Well, it turns out that both functions exist, and they're declared in a file called ctype.h. So let's add that file to my includes. include ctype.h. And now let's utilize both of those functions, replacing first my if condition as follows. if islower s bracket i, thereby returning true or false if the ith character in s is a lower case letter. And let's now replace my arithmetic expression here with simply toupper of s bracket i, thereby returning the uppercase equivalent of the ith character in s if it's lower case. I'm going to leave my else block alone, because if the letter is not lowercase, I still want to print it out unchanged. And let's now compile this program. Make [? capitalize1. ?] Let's now run the program with capitalize1. And let's now type a word like hello in all lowercase. H-E-L-L-O, Enter, and it indeed prints in all uppercase. Let's try one more scenario, though, this time inputting my own name with the first letter, D, capitalized already, just in case I messed something up in my own code with the capitalization of that char. Enter, but no, DAVID in all caps prints this time as expected.