Mid POint CIrcle Algorithm In CG

#include <graphics.h>  
#include <stdlib.h>  
#include <math.h>  
#include <stdio.h>  
#include <conio.h>  
#include <iostream.h>  
  
class bresen  
{  
    float x, y,a, b, r, p;  
    public:  
    void get ();  
    void cal ();  
};  
    void main ()  
    {  
    bresen b;  
    b.get ();  
    b.cal ();  
    getch ();  
   }  
    Void bresen :: get ()  
   {  
    cout<<"ENTER CENTER AND RADIUS";  
     cout<< "ENTER (a, b)";  
    cin>>a>>b;  
    cout<<"ENTER r";  
    cin>>r;  
}  
void bresen ::cal ()  
{  
    /* request auto detection */  
    int gdriver = DETECT,gmode, errorcode;  
    int midx, midy, i;  
    /* initialize graphics and local variables */  
    initgraph (&gdriver, &gmode, " ");  
    /* read result of initialization */  
    errorcode = graphresult ();  
    if (errorcode ! = grOK)    /*an error occurred */  
    {  
        printf("Graphics error: %s \n", grapherrormsg (errorcode);  
        printf ("Press any key to halt:");  
        getch ();  
        exit (1); /* terminate with an error code */  
    }  
    x=0;  
    y=r;  
    putpixel (a, b+r, RED);  
    putpixel (a, b-r, RED);  
    putpixel (a-r, b, RED);  
    putpixel (a+r, b, RED);  
    p=5/4)-r;  
    while (x<=y)  
    {  
        If (p<0)  
        p+= (4*x)+6;  
        else  
        {  
            p+=(2*(x-y))+5;  
            y--;  
        }  
        x++;  
        putpixel (a+x, b+y, RED);  
        putpixel (a-x, b+y, RED);  
        putpixel (a+x, b-y, RED);  
        putpixel (a+x, b-y, RED);  
        putpixel (a+x, b+y, RED);  
        putpixel (a+x, b-y, RED);  
        putpixel (a-x, b+y, RED);  
        putpixel (a-x, b-y, RED);  
    }  
}