Bezier Curve

#include
#include

void circl(int x, int y, int r)
{
int x1,y1,p;
x1=0;
y1=r;
p=3-2*r;

while(x1 {
plotcircle(x,y,x1,y1);
if(p<0)
p=p+4*x1+6;
else
{
p=p+4*(x1-y1)+10;
y1=y1-1;
}
x1=x1+1;
}

if(x1==y1)
plotcircle(x,y,x1,y1);
}

plotcircle(int x,int y, int x1, int y1)
{
putpixel(x+x1,y+y1,RED);
putpixel(x-x1,y+y1,RED);
putpixel(x+x1,y-y1,RED);
putpixel(x-x1,y-y1,RED);
putpixel(x+y1,y+x1,RED);
putpixel(x-y1,y+x1,RED);
putpixel(x+y1,y-x1,RED);
putpixel(x-y1,y-x1,RED);
return 0;
}

void cubic(int x1,int y1,int x2, int y2, int x3, int y3, int x4, int y4, int color)
{
int Cx[4],Cy[4];
int ax,ay,bx,by,cx,cy,dx,dy,x,y;
int i=0;
double stepsize,t;
Cx[0]=x1;
Cy[0]=y1;
Cx[1]=x2;
Cy[1]=y2;
Cx[2]=x3;
Cy[2]=y3;
Cx[3]=x4;
Cy[3]=y4;
for(i=0;i<4;i++)
{
setcolor(color);
circl(Cx[i],Cy[i],3);
}
setcolor(color);
ax=-Cx[0]+3*Cx[1]+(-3*Cx[2])+Cx[3];
ay=-Cy[0]+3*Cy[1]+(-3*Cy[2])+Cy[3];
bx=3*Cx[0]+(-6*Cx[1])+3*Cx[2];
by=3*Cy[0]+(-6*Cy[1])+3*Cy[2];
cx=-3*Cx[0]+3*Cx[1];
cy=-3*Cy[0]+3*Cy[1];
dx=Cx[0];
dy=Cy[0];
for(i=0;i<4;i++)
{
putpixel(Cx[i],Cy[i],RED);
}
setcolor(WHITE);
for(i=0;i<3;i++)
{
line(Cx[i],Cy[i],Cx[(i+1)%4],Cy[(i+1)%4]);
}
setcolor(RED);
stepsize=1.0/1000.0;
for(i=0;i<1000;i++)
{
t=stepsize*(double)i;
x=ax*(t*t*t)+bx*(t*t)+cx*t+dx;
y=ay*(t*t*t)+by*(t*t)+cy*t+dy;
putpixel(x,y,RED);
}
}

main()
{
int gd,gm,x,y;
detectgraphI&gd,&gm);
initgraph(&gd,&gm,"..\\bgi ");

cleardevice();
cubic(50,300,100,50,250,50,350,300,6);
getch();
cleardevice();
cubic(50,300,350,300,100,50,250,50,6);
getch();
cleardevice();
cubic(50,300,100,50,350,300,250,50,6);
getch();
cleardevice();
cubic(350,300,50,300,100,50,250,50,6);
getch();

return 0;
}