For the cat, the function sound() declaration and call will look:

#include <iostream>
using namespace std;

// Function declaration
void sound() {
    cout << "meow!" << endl;
}

int main() {
    // Call the function to be executed 
    sound();

    return 0;
}

Remember:

• you have to declare a function before calling it.
• you can declare the function as many times as you want.

You have met functions at the beginning of your C++ programming path. main() - is the pre-defined function that is used to execute the code.