#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,e,inc_x,inc_y,x,y,c1,c2,i;

  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 */
  line(p1.x,p1.y,p2.x,p2.y); getche();

  dx=abs(p2.x-p1.x); dy=abs(p2.y-p1.y);
  if (p2.x >= p1.x) inc_x=1; else inc_x=-1;
  if (p2.y >= p1.y) inc_y=1; else inc_y=-1;
  x=p1.x; y=p1.y;  putpixel(x,y,1);
  if (dx > dy) {
    e=2*dy-dx; c1=2*(dy-dx); /*  select upper one */
    c2=2*dy;
    for (i=0; i<dx; i++) {
      if (e >= 0) { y+=inc_y; e+=c1; } else e+=c2;
      x+=inc_x; putpixel(x,y,14);
    }
  }
  else {
    e=2*dx-dy; c1=2*(dx-dy); /*  select upper one */
    c2=2*dx;
    for (i=0; i<dy; i++) {
      if (e >= 0) { x+=inc_x; e+=c1; } else e+=c2;
      y+=inc_y; putpixel(x,y,14);
    }
  }
  getche();
  closegraph();                 /* Return the system to text mode       */
}