Prototyping Classes in C++

Hello, I was wondering if it was possible to prototype classes in C++. Rather than have everything above the main function, I`d like to organize it better and put certain classes below the main function as well.

I know about the possibility of prototyping functions, which does help out quite a bit! Just hoping any of you know of any possibility of doing the same for classes.

I`ll post my code for my project, which is literally just me learning classes in C++. Just incase anybody here needed it.

#include <iostream>

using namespace std;

//The class I wish to appear below the "int main" function.
class TestClass{
public:
    void sayings()
    {
        cout << "Your computer is dead to me." << endl;
    }
};

//Just the main function, which prints out the sayings function within the TestClass class.
int main()
{
    TestClass testObject;
    testObject.sayings();
    
    return 0;
}