C++ Program to implement Bresenham's circle algorithm (Graphics)

In computer graphics, the midpoint circle algorithm is an algorithm used to determine the points needed for drawing a circle. Bresenham's circle algorithm is derived from the midpoint circle algorithm. The algorithm can be generalized to conic sections.^[1]

https://en.wikipedia.org/wiki/Midpoint_circle_algorithm

Program

#include <iostream.h>
#include <graphics.h>
#include <conio.h>
#include <dos.h>
void circlebres(float x1,float y1,float r)
{
float x,y,p;
x=0;
y=r;
p=3-(2*r);
while(x<=y)
{
putpixel(x1+x,y1+y,WHITE);
putpixel(x1-x,y1+y,WHITE);
putpixel(x1+x,y1-y,WHITE);
putpixel(x1-x,y1-y,WHITE);
putpixel(x1+y,y1+x,WHITE);
putpixel(x1+y,y1-x,WHITE);
putpixel(x1-y,y1+x,WHITE);
putpixel(x1-y,y1-x,WHITE);
x=x+1;
if(p<0)
{
p=p+4*(x)+6;
}
else
{
p=p+4*(x-y)+10;
y=y-1;



}
delay(20);

}
}
void main()
{
float x1,y1,r;
int gd=DETECT,gm;
initgraph(&gd,&gm,"C:\\Tc\\BGI");
cout<<"Enter the starting co-ordinates of a center:";
cin>>x1>>y1;
cout<<"Enter the value of radius:";
cin>>r;
circlebres(x1,y1,r);
getch();
closegraph();
}