C++ Program to show animated bouncing ball

Program 
#include<iostream.h>
#include<conio.h>
#include<graphics.h>
#include<dos.h>
void main()
{
clrscr();
int gd=0,gm,x=20,flag=0,y=200,uplimit=250;
initgraph(&gd,&gm,"C:\\Tc\\BGI");
while(!kbhit())
{
setcolor(4);
line(0,400,679,400);
if(flag==0)
{
y+=2;
x+=1;
if(y>=385)
flag=1;
}
if(flag==1)
{
y-=2;
x+=1;
if(y<=uplimit)
{
flag=0;
uplimit+=20;

}
}

setcolor(15);
fillellipse(x,y,15,15);
delay(15);
setcolor(0);
setfillstyle(1,10);
fillellipse(x,y,15,15);
cleardevice();
}

getch();
}