#include <iostream>
#include <locale>
#include <string>
 
using namespace std;
 
class numfmt: public numpunct<char> {
  string do_grouping() const { return "\3"; }
  char_type do_thousands_sep() const { return ','; }
};
 
int main()
{
  cout.imbue ( locale ( locale(), new numfmt ) );
  cout<< fixed << 4.89281e+07 <<endl;
}

#include <iostream>
#include <math.h>
using namespace std;
 
double xyz[3];
double mark[3];
 
void markoff(double x, double y, double z)
{
  mark[0] = y;
  mark[1] = z;
  mark[2] = ((3*y*z) - x);
 
  cout<<"x = "<<mark[0]<<" y = "<<mark[1]<<" z = "<<mark[2]<<endl;
}
 
int main()
{
 
  xyz[0] = 1;
  xyz[1] = 1;
  xyz[2] = 1;
 
  while( mark[2] < (pow(10.0,101.0)) )
    {
      markoff( xyz[0], xyz[1], xyz[2] );
 
      xyz[0] = mark[0];
      xyz[1] = mark[1];
      xyz[2] = mark[2];
    }
 
 
  return 0;
}
 
 
output:
 
-bash-2.05b$ ./a.out
x = 1 y = 1 z = 2
x = 1 y = 2 z = 5
x = 2 y = 5 z = 29
x = 5 y = 29 z = 433
x = 29 y = 433 z = 37666
x = 433 y = 37666 z = 4.89281e+07
x = 37666 y = 4.89281e+07 z = 5.52878e+12
x = 4.89281e+07 y = 5.52878e+12 z = 8.11538e+20
x = 5.52878e+12 y = 8.11538e+20 z = 1.34604e+34
x = 8.11538e+20 y = 1.34604e+34 z = 3.2771e+55
x = 1.34604e+34 y = 3.2771e+55 z = 1.32333e+90
x = 3.2771e+55 y = 1.32333e+90 z = 1.30101e+146

#include <iostream>
#include <math.h>
using namespace std;

double xyz[3];
double mark[3];

void markoff(double x, double y, double z)
{
  mark[0] = y;
  mark[1] = z;
  mark[2] = ((3*y*z) - x);

  cout<<"x = "<<mark[0]<<" y = "<<mark[1]<<" z = "<<mark[2]<<endl;
}

int main()
{

  xyz[0] = 1;
  xyz[1] = 1;
  xyz[2] = 1;

  cout.setf ( ios::fixed, ios::floatfield );
  while( mark[2] < (pow(10.0,101.0)) )
    {
      markoff( xyz[0], xyz[1], xyz[2] );

      xyz[0] = mark[0];
      xyz[1] = mark[1];
      xyz[2] = mark[2];
    }

  return 0;
}