Circle

#include <iostream>
#include <graphics.h>
#define color YELLOW
#define DELAY 50
using namespace std;
void Put8Pixel(int x, int y, int x0, int y0)
{
    putpixel(x + x0, y + y0, color);
    putpixel(y + y0, x + x0, color);
    putpixel(y + y0, -x + x0, color);
    putpixel(x + x0, -y + y0, color);
    putpixel(-x + x0, -y + y0, color);
    putpixel(-y + y0, -x + x0, color);
    putpixel(-y + y0, x + x0, color);
    putpixel(-x + x0, y + y0, color);
}

void myCircle(int x0, int y0, int R)
{
    float p = 1 - R;
    int x = 0;
    float y = R;
    Put8Pixel(x, y, x0, y0);
    cout<<"("<<x<<","<<y<<")   "<<p<<endl;
    while (x<y)
    {
        if (p<0)
        {
            //cout<<"("<<x<<","<<y<<")  : "<<"p = 2*"<<x<<"+3 = "<<p<<endl;
            p += 2*x + 3;
        }
        else
        {
            //cout<<"("<<x<<","<<y<<")  : p = 2*("<<x<<"-"<<y<<") +5 = "<<p<<endl;
            p += 2*(x - y) + 5;
            y--;
        }
        x++;
        Put8Pixel(x, y, x0, y0);
        //delay(DELAY);
    }
}


int main()
{
    int gd,gm=VGAMAX; gd=DETECT;
    initgraph(&gd,&gm,NULL);        // khoi tao cua so do hoa
    int x = 120, y = 120, R = 100;
    myCircle(x, y, R);
    cin.get();
    return 0;
}