Main must return a value

Question

I've been working through the "Programming: Principles and Practice using C++" book, and this example was meant to illustrate how data can be lost in type conversions. But when I tried to execute it, it keeps telling me 'Main' : must return a value. I tried using "return 0;" after the curly brace for the while loop, but then it gave errors around "Unresolved externals".

I've copied the code from the book to Visual Studio and everything else I've copied has worked as expected - would anyone be able to tell me how I could fix this please? I don't know why it's happening with this specific example or how to make it stop asking for a return value.

Sorry if this is dumb, I'm very inexperienced and I've tried googling for an answer, but suggested solutions like "return 0" don't work :)!

#include "std_lib_facilities.h"

int main()
{
    double d = 0;

    while (cin >> d)
    {

        int i = d;
        char c = i;
        int i2 = c;
        cout << "d==" << d
        << " i==" << i
        << " i2==" << i2
        << " char(" << c << ")\n";
    }
}

Answer 1

I tried using "return 0;" after the curly brace for the while loop, but then it gave errors around "Unresolved externals".

That's a separate, unrelated problem uncovered by fixing the first one. Add the return, then deal with the unresolved externals error.

Answer 2

If that's your whole program, you're unresolved external is most likely iostream. You need to include that and use the correct namespace.

Consider the following code:

#include <iostream>

using namespace std;

int main() {
   cout << "Hello World!" << endl;
   return 0;
}

Better yet, forgo the using statement and use std::cout so that you don't have to worry about namespace collision. See this question Why is “using namespace std;” considered bad practice?

#include <iostream>

int main() {
   std::cout << "Hello World!" << std::endl;
   return 0;
}