#include <stdio.h>
#include <conio.h>
#include <graphics.h>
main()
{
 int gd=DETECT;
 int gm=DETECT;
 int dx,dy,Xa,Ya,Xb,Yb,c,r,inc1,inc2,g,f;
 detectgraph(&gm, &gd);
 initgraph(&gm,&gd,"c:\\turboc\\tc\\bgi");
 cleardevice();

 printf("Enter your first X-coordinates: ");
 scanf("%d",&Xa);
 printf("enter your first Y-coordinates: ");
 scanf("%d",&Ya);
 printf("enter your second X-coordinates: ");
 scanf("%d",&Xb);
 printf("enter your second Y-coordinates: ");
 scanf("%d",&Yb);
 clrscr();
 dx=Xb-Xa;
 dy=Yb-Ya;
 if(dx>dy)
 {
  if(dx<0)
  {
   c=Xa;
   r=Ya;
   f=Xb;
  }
  else
  {
   c=Xb;
   r=Yb;
   f=Xa;
  }
  inc1=2*dy;
  g=2*dy-dx;
  inc2=2*(dy-dx);
  if(dy<0)
   dx=-dx;
  if(dx>0)
  {
   do
   {
    c=c+1;
    if(g<=0)
    {
     r=r+1;
     g=g+inc2;
    }
    else
    {
     g=g+inc1;
     putpixel(c,r,RED);
     }
   }while(c<f);
  }
  else
  {
   do
   {
    putpixel(c,r,RED);
    c=c+1;
    if(g>0)
    {
     r=r-1;
     g=inc2;
    }
    else
    {
     g=g+inc1;
     }
   }while(c<f);
  }
 }
}