程式碼如下，我預設讓y不等於零的時候輸出，請問為什麼y等於零時也會輸出
#include <stdio.h>
#include <math.h>
#include <time.h>
int main()
{
while(1)
{
double a,b,c,x;
double start,end,d;
double y;
printf("input a,b,c:");
scanf("%lf %lf %lf",&a,&b,&c);
printf("input start,end,d:");
scanf("%lf %lf %lf",&start,&end,&d);
end+=d;
for(x=start; x<end; x+=d)//from x to end
{
y=a*x*x+b*x+c;
if(y!=0)
{
printf("x=%lf\t",x);
printf("y=%lf\n",y);
}
}
printf("\n");
}
}
