[Solved] Program keeps returning Segmentation Fault [closed]

(1) isalpha(argv[1]) is wrong. This function expects a single character, but you are passing a pointer-to-string. That will certainly not give you any kind of expected result, and it’s probably Undefined Behaviour into the bargain. You either need to loop and check each character, use a more high-level library function to check the entire string, … Read more