Question

how do I use void main in this system for C++

Answer 1

#include <iostream>

void poo()

{

    std::cout << "poo\n";

}

int main()

{

    poo();

    return 0;

}

Answer 2

If I understand your question correctly, you're asking how do you have a main function in C++ that returns void. (i.e.)

#include <iostream>

void main() {
    std::cout << "Hello, World";

    return;
}

Short answer - you don't.  C++ requires main() to return an int.  To be honest, even when C "allowed" it, the app still returned an error code.  It was just always 0.  This is functionally equivalent to what a void function did in C:

#include <iostream>

int main() {
    std::cout << "Hello, World";

    return 0;
}