#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,p,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=Xa-Xb;
 dy=Ya-Yb;
 p=2*dy-dx;
 if(dx>dy)
 {
 if(dx>0)
 {
   c=Xb;
   r=Yb;
   f=Xa;
 }
 else
 {
  c=Xa;
  r=Ya;
  f=Xb;
 }
 putpixel(c,r,RED);
 do
 {
   c=c+1;
   if(p<0)
    p=p+2*dy;
   else
   {
    r=r+1;
    p=p+2*(dy-dx);
   }
   putpixel(c,r,RED);
 }while(c<f);
 }
 else
 {
 if(dx>0)
 {
   c=Xb;
   r=Yb;
   f=Xa;
 }
 else
 {
  c=Xa;
  r=Ya;
  f=Xb;
 }
 putpixel(c,r,RED);
 do
 {
   c=c+1;
   if(p<0)
    p=p+2*dy;
   else
   {
    r=r+1;
    p=p+2*(dy-dx);
   }
   putpixel(c,r,RED);
 }while(c<f);
 }
 getche();
}