floating point exception in C code !

Question

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

int main ()
{
    FILE *fp;
    fp=fopen("output","w");
    float t,y=0,x=0,e=5,f=1,w=1;
    for (t=0;t<10;t=t+0.01)
    {
        if( y==inf && y== nan) 
            break;
        fprintf(fp,"%lf\t%lf\n",y,x);
        y = y + ((e*(1 - x*x)*y) - x + f*cos(w*t))*t;
        x = x + y*t;
    }
    return 0;
}

Why is the ouput giving infinite and NAN values?

Answer 1

Your calculation is blowing up. Just look at the values printed out for x and y and you will see they start to get very large and then turn info inf. Because your conditional is wrong, you wind up using inf in the calculation which turns into nan.