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

//
//   estimate machine epsilon
//   For double precision, expect eps = 2^-53

int main()
{
  float f1,f2,res;
  double d1,d2,res2,diff;

  d2    =1.12345678902000000000000;
  d1    =1.12345678901234567890123;
//d2-d1 =0.00000000000765432109877
  diff  =7.65432109877e-12;

  f2=d2;
  f1=d1;

  res = f2-f1;
  res2 = d2-d1;

  printf("original numbers in double %27.21lf \t%27.21lf \n", d2,d1);
  printf("original numbers in  float %27.21lf \t%27.21lf \n", f2,f1);

  printf("float and double differences %23.18lf \t%13.11E \n", res, res2);
  printf("\nrelative error using doubles %E \n",(res2-diff)/diff);
  return 0;
}