为什么我的win-TC输不出图形？

#include "stdio.h"
#include "conio.h"
#include<graphics.h>
#include<math.h>
int main(void)
{
int gd=DETECT,gm;
float d1,d2;
float a=150,b=150;
float x,y,x0,y0;
x0=150;
y0=150;
x=0;y=b;
initgraph(&gd,&gm," ");
d1=b*b+a*a*(-b+0.25);

putpixel(x+x0,y+y0,15);
putpixel(-x+x0,-y+y0,4);
putpixel(x+x0,-y+y0,5);
putpixel(-x+x0,y+y0,6);
while(b*b*(x+1)<a*a*(y-0.5))
{
if(d1<=0)
{d1+=b*b*(2*x+3);
x++;
}
else
{d1+=b*b*(2*x+3)+a*a*(-2*y+2);
x++;y--;
}
putpixel(x+x0,y+y0,5);
putpixel(-x+x0,-y+y0,5);
putpixel(-x+x0,y+y0,6);
putpixel(x+x0,-y+y0,2);
}

d2=b*b*(x+0.5)*(x+0.5)+a*a*(y-1)*(y-1)-a*a*b*b;
while(y>0)
{
if(d2<=0)
{
d2+=b*b*(2*x+2)+a*a*(-2*y+3) ;
x++;y--;
}
else
{ d2+=a*a*(-2*y+3);