#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <graphics.h>
void main() {
int    GraphDriver;             /* The Graphics device driver           */
int    GraphMode;               /* The Graphics mode value              */
struct point { int x,y; } p1,p2;
int dx,dy,d,inc_r,inc_ru,x,y;

  printf("give me the first point--->"); scanf("%d %d",&p1.x,&p1.y);
  printf("give me the second point--->"); scanf("%d %d",&p2.x,&p2.y); 
  printf("(%d,%d) to (%d,%d)\n",p1.x,p1.y,p2.x,p2.y); 
  getche();

  GraphDriver = DETECT;                 /* Request auto-detection       */
  initgraph( &GraphDriver, &GraphMode, "" ); /* just increasing p1 - p2 */
  dx=p2.x-p1.x; dy=p2.y-p1.y; d=2*dy-dx; inc_r=2*dy; inc_ru=2*(dy-dx);
  x=p1.x; y=p1.y;  putpixel(x,y,1);
  if (dx > dy) {
    d=2*dy-dx; inc_r=2*dy; inc_ru=2*(dy-dx);
    while (x < p2.x) {
      if (d <= 0) { d+=inc_r; x++; }
      else { x++; y++; d+=inc_ru; }
      putpixel(x,y,1);
    }
  }
  else {
    d=2*dx-dy; inc_r=2*dx; inc_ru=2*(dx-dy);
    while (y < p2.y) {
      if (d <= 0) { d+=inc_r; y++; }
      else { x++; y++; d+=inc_ru; }
      putpixel(x,y,1);
    }
  }
  getche();
  closegraph();                 /* Return the system to text mode       */
}