// Computes N! for an integer N >= 0 
int F = 1;
// Invariant: F == (J-1)!
for (int J = 1; J <= N; ++J)
   F *= J;

// Computes an approximation to eX for a real X
double	T = 1.0;
double	S = 1.0;
int	K = 1; 
// Invariant: T == XK-1/(K-1)! and 
// S == 1+X+X2/2!+...+XK-1/(K-1)!
while (K <= N)
{  T *= X/K;
   S += T;
   ++K;
}  // end while