Step 4 of 6

bool, auto and range-for

A few small upgrades:

bool is a real type with true and false (no include needed).
auto lets the compiler deduce a variable's type from its initializer: auto x = 3.5; is a double.
The range-based for loop visits every element of a string, array or container:

std::string s = "awp";
for (char c : s) {
    std::cout << c << "\n";
}

Your turn: write int count_vowels(std::string s) that counts a e i o u (lowercase only) using a range-based for loop.