CERCLE DISCRET (POINT PAR POINT) EN C++

int xd=0,yd=0;
int n=0;
int s=0;
/* Plot generates a point of the circle */
void plot(x,y)
int x,y;
{
  s++;
  cout<<"Val Of X= "<<x+xd<< " and Val of y= "<<y+yd;
}
//------------------------------------------------------void main(void)
{
  s=0;
  int ri,x,y; /* Integer part of radius point */

 float a,rph,rpxo,rmxo,rpyo,rmyo; /* constants */
 float xoph,xomh,yoph,yomh;
 float r,xo,yo; /* radius and center */
 double d; /* control value */
 float tmp,tmp1; /* temp. value */
 n=0;
//Provide the radius and the center:R,xo,yo
 
 cout<<" val of R= ";
 sin>>r;
 
 xo=0;yo=0 ;
 ri=(int)r; /* integer part of the radius */
 r=r-0.5; /* circle of radius r'=r-0.5 is generated */
 a=r-ri; /* corresponding fractional part of radius */
/* CIRCLE WITH SMALL RADIUS */
if (ri<=1)
{
    tmp=2*r+1;
    for(x=-2;x<=2;x++) /* the generation is brute force */
    for(y=-2;y<=2;y++)
    {
       tmp1=x*x+y*y-r*r;
       if ((tmp1>=0) && (tmp1<tmp))
       plot(x,y);
    }
}
else
{
   // ri>1
   /* GENERAL CASE */
   /* Initialization of loop constants */
   rph=r+0.5;
   rpxo=r; rmxo=r-xo; rpyo=r+yo; rmyo=r-yo;
   xoph=xo+0.5; xomh=xo-0.5; yoph=yo+0.5; yomh=yo-0.5;
/* STARTING POINT COMPUTATION */
    y=0;
    d=((ri-rpxo)*(ri+rmxo)+yo*yo)/2.0; /* Initial value of d for (ri,0) */
   if (d<(a+xo)) /* does (ri+1,0) belong to the circle ? */
{ plot(ri+1,0); /* (ri+1,0) does belong to the circle */
if (d>=0) { plot(ri,0); x=ri;} /* (ri,0) belongs also to the circle */
else { x=ri+1; d+=ri-xomh;} /* (ri,0) doesn't belong to the circle */
}
else if ((d>=0) && (d<rph)) /* does (ri,0) belong to the circle ? */
{ plot(ri,0);
  x=ri;
}
else /* if neither (ri+1,0) nor (ri,0) belong to the
circle then (ri-1,0) does */
 {
   x=ri-1; plot(x,0);
   d+=xoph-ri;
 }
/* END OF STARTING POINT PHASE */
/* GENERATION OF QUADRANT 1 */
while (x>0)
 {
   if (d<(rpyo-y)) /* Type (a) ? */
 {  d+=y-yomh;
 y++;
 plot(x,y);
}
else
{ d+=xoph-x;
x--;
if (d>=0) plot(x,y); /* Type (b) ? */
else
{ d+=y-yomh; /* Type (c) !*/
y++;
plot(x,y);
}
}
}
/* END OF GENERATION OF QUADRANT 1 */
/* LIMIT POINTS BETWEEN QUADRANT #1 AND QUADRANT #2 */
if (d<(rpyo-y)) /* Does (0,y+1) belong to the circle ? */
{ d+=xoph; plot(0,y+1); x--; plot(-1,y); }
/* GENERATION OF QUADRANT 2 */
while (y>0 )
{ if (d<(rmxo+x))
{
d+=xoph-x;
x--;
plot(x,y);
}
else
{ d+=yoph-y;
y--;
if (d>=0) plot(x,y);
else
{ d+=xoph-x;
  x--;
plot(x,y);
}
}
}
/* END OF GENERATION OF QUADRANT #2 */
/* LIMIT POINTS BETWEEN QUADRANT #2 AND QUADRANT #3 */
if (d<(rpxo+x))
{ d+=yoph; plot(x-1,0); y--; plot(x,-1); }
/* GENERATION OF QUADRANT #3 */
while (x<0)
{ if (d<(rmyo+y))
{ d+=yoph-y;

y--;
plot(x,y);
}
else
{ d+=x-xomh;
x++;
if (d>=0) plot(x,y);
else
 { d+=yoph-y;
   y--;
   plot(x,y);
 }
}
}
/* END OF GENERATION OF QUADRANT #3 */
/* LIMIT POINTS BETWEEN QUADRANT #3 AND QUADRANT #4 */
if (d<(rmyo+y))
{ d-=xomh; plot(0,y-1); x++; plot(1,y); }
/* GENERATION OF QUADRANT #4 */
while (y<0)
{ if (d<(rpxo-x))
  { d+=x-xomh;
    x++;
    plot(x,y);
  }
else
{  d+=y-yomh;
   y++;
   if ((d>=0)&&(y)) plot(x,y);
   else
{  d+=x-xomh;
   x++;
   if (y) plot(x,y);
}
}
}
/* END OF GENERATION OF QUADRANT #4 */
} /* END OF THE GENERAL CASE */
}
//------------------------------------------------------
  GO and test