DDA Line drawing program in C++

/* DDA Line drawing program*/
#include<dos.h>
#include<iostream.h>
#include<graphics.h>
#include<math.h>
#include<conio.h>
void main()
{
float x,y,x1,y1,x2,y2,dx,dy,length;
int i,gd=DETECT,gm;
//Read two end points of line
cout<<"Enter the value of x1 :\t";
cin>>x1;
cout<<"Enter the value of y1 :\t";
cin>>y1;
cout<<"Enter the value of x2 :\t";
cin>>x2;
cout<<"Enter the value of y2 :\t";
cin>>y2;

/* Initialize graphics mode*/
 initgraph(&gd,&gm,"c://tc//bgi");

dx=abs(x2-x1);
dy=abs(y2-y1);
if (dx >= dy)
   {
   length = dx;
   }
   else
   {
   length = dy;
   }
dx = (x2-x1)/length;
dy = (y2-y1)/length;
x = x1 + 0.5;  /* Factor 0.5 is added to round the values */
y = y1 + 0.5;  /* Factor 0.5 is added to round the values */
i = 1;         /* Initialise loop counter */
while(i <= length)
   {
    putpixel(x,y,WHITE);
    x = x + dx;
    y = y + dy;
    i = i + 1;
    delay(50); /* Delay is purposely inserted to see*/
    }
getch();
}

For OUTPUT check out the video! :