#include<grophics.h>
main()
{
   int graphdriver=DETECT;
   int graphdriver,x;
   initgraph(&graphdriver,&graphmode);
cleardevice();
for(x=20;i<=300;i+=16）
{
  putpixel(x,20,1);
  putpixl(x+4,20,2);
}
getch();
closegraph();
}
怎么不能运行呢