Quadratic equation in C, Objective-C, C++

Example for versions Borland C++ Builder 6, Microsoft Visual C++ 9 (2008), g++ 3.4.5, gcc 3.4.5, gcc 3.4.5 (Objective-C), gcc 4.2.4, tcc 0.9.25

This example works both for C and C++, as well as for Objective-C which is superset of C. 

#include <math.h> 
#include <stdio.h>

int main()
{
  int A, B, C;
  double D;
  printf("A = ");
  scanf("%d", &A);
  if (A == 0) {
    printf("Not a quadratic equation.\n");
    return 0;
  }
  
  printf("B = ");
  scanf("%d", &B);
  printf("C = ");
  scanf("%d", &C);

  D = B * B - 4 * A * C;
  if (D == 0) {
    printf("x = %f\n", -B / 2.0 / A);
    return 0;
  }
  
  if (D > 0) {
    printf("x1 = %f\nx2 = %f\n",
           (-B + sqrt(D)) / 2.0 / A, (-B - sqrt(D))/ 2.0 / A);
  } else {
    printf("x1 = (%f, %f)\nx2 = (%f, %f)\n",
           -B / 2.0 / A, sqrt(-D) / 2.0 / A, -B / 2.0 / A, -sqrt(-D) / 2.0 /A);
  }
  return 0;
}