When is it appropriate to use void functions?

[cozier]

I was wondering if someone could help explain to me when it is appropriate to use void as a function type. Additionally, is it something you can/should use in your main() function?

This is a case where it came up on a project I was working on as an example of where I have stumbled upon it.

Thanks for your time!

  #include <iostream>
using namespace std;

void swap_numbers( int&, int&); //Function prototype

void main()

{

int num1, num2; // Initializing num1 & num2 where user will input integer

cout << "Please enter two integers: ";
cin >> num1;
cin >>num2;

swap_numbers (num1, num2); // Calling the function swap_numbers
cout << "The numbers reversed: " 
	 << num1 << ' '<< num2 << endl; //Printing out the switched numbers

}

void swap_numbers (int & a, int & b)

{
    int x; // Using as a temp. place holder 
    x = a;
    a = b;
    b = x;
}

[Cubbi]

Yes, std::swap() and other swaps are good examples of functions that do not return a value. Other common examples: std::vector::push_back(), std::sort(), std::srand(), std::mutex::lock(), etc.

And no, main() can never return void, many compilers will reject your program because of that error.

[cozier]

Oh ok. I was a bit confused because a few of the prompt shells the teacher has given out during class include void main and just happen to be thinking about that for some odd reason. Thanks again!