What's an effective way to parse command line parameters in C++?

Question

Is there a really effective way of dealing with command line parameters in C++?

What I'm doing below feels completely amateurish, and I can't imagine this is how command line parameters are really handled (atoi, hard-coded argc checks) in professional software.

// Command line usage: sum num1 num2

int main(int argc, char *argv[])
{
   if (argc < 3)
   {
      cout << "Usage: " << argv[0] << " num1 num2\n";
      exit(1);
   }

   int a = atoi(argv[1]);
   int b = atoi(argv[2]);
   int sum = a + b;

   cout << "Sum: " << sum << "\n";

   return 0;
}