#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <graphics.h>
struct POINT { int x,y; };
void main() {
  int Drv,mode,dx,dy,i;
  struct POINT p1,p2;
  float x,y,inc;

  printf("give me the first line point -->"); scanf("%d %d",&p1.x,&p1.y);
  printf("give me the second line point -->"); scanf("%d %d",&p2.x,&p2.y);
  Drv=DETECT; initgraph(&Drv,&mode,"");

  setcolor(3); line(p1.x,p1.y,p2.x,p2.y); getche(); /* clearviewport(); */

  /* dda algorithm */
  dx=p2.x-p1.x; dy=p2.y-p1.y; x=p1.x; y=p1.y; putpixel(x,y,14);
  if (abs(dx) > abs(dy)) {
    inc=dy/(float)dx;
    if (dx >= 0)
      for (i=p1.x+1; i<=p2.x; i++) { x=i; y=y+inc; putpixel(x,y,14); }
    else
      for (i=p1.x-1; i>=p2.x; i--) { x=i; y=y-inc; putpixel(x,y,14); }
  }
  else { /* abs(dx <= abs(dy) */
    inc=dx/(float)dy;
    if (dy >= 0)
      for (i=p1.y+1; i<=p2.y; i++) { y=i; x=x+inc; putpixel(x,y,14); }
    else
      for (i=p1.y-1; i>=p2.y; i--) { y=i; x=x-inc; putpixel(x,y,14); }
  }

  getche(); closegraph();
}