Why would I run strlen() on the second one but not on the first one? Presumably I know that I defined an array of chars and not a cstring? Or if I forget, could

Why would I run strlen() on the second one but not on the first one? Presumably I know that I defined an array of chars and not a cstring? Or if I forget, couldn't I forget in the first case too? Once I defined it, they're both just char[4]s.