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

#define TRUNCATION 1e-10

double factorial(int n)
{
  int loop;
  double fac;
  for (loop = 1, fac = 1.0; loop <= n; loop++)
  {
    fac *= loop;
  }
  return fac;
}

int main()
{
  int n;
  double x, term, sum;

  printf("       x       exp(-x)       series       terms\n");

  for (x = 0.0; x < 100.0; x += 10.0)
  {
    sum = 0.0;

    n = 0;
    term = 1;
    while (fabs(term) > TRUNCATION)
    {
      term = pow(-1, n) * (pow(x, n) / factorial(n));
      sum += term;
      n++;
    }

    printf("%12f %12g %12g %5d\n", x, exp(-x), sum, n - 1);
  }
  return 0;
}