This is what I have so far. I realized that when counting letters there are more symbols you must exclude, but I am not sure how to do that. Also, my program isn't running for some reason and I am not sure why...
Not exactly sure what you're asking, but here goes. There is an entire family of issomething() functions - isalpha, isdigit, etc. They can be used in combination with the not operator,
! so that something that is NOT a letter can be tested for.
As for why your program won't run, we'd need to know what command you're actually entering to try and run a program, what directory you are in at the time, and whether the file that you're trying to run exists and whether it's an executable file or source code.
Without that info, here's my best suggestion. Switch to the directory that contains the executable, and run it. Say that you want to run caesar. Switch to the directory with the caesar executable file and then call it like this: