#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <graphics.h>
#define TOP    8
#define BOTTOM 4
#define LEFT   2
#define RIGHT  1
#define ACC(c1,c2) ((c1 == 0) && (c2 == 0))
#define REJ(c1,c2) ((c1 & c2) != 0)
int getcode (int x, int y) {
  int code;
  if (y > 479) code=BOTTOM;
  else if (y < 0) code=TOP;
  else code=0;
  if (x > 639) code |= RIGHT;
  else if (x < 0) code |= LEFT;
  return code;
}
void main() {
int    Driver;             /* The Graphics device driver           */
int    Mode;               /* The Graphics mode value              */
struct point { int x,y; } p1,p2;
int c2,c1;

  printf("give me the 1st line point--->"); scanf("%d %d",&p1.x,&p1.y);
  printf("give me the 2nd line point--->"); scanf("%d %d",&p2.x,&p2.y);
  getche();

  c1=getcode(p1.x,p1.y); c2=getcode(p2.x,p2.y);
  if (REJ(c1,c2)) printf("line cannot draw !!!\n");
  else {
    printf("(%d,%d) --> code=%d\n",p1.x,p1.y,c1);
    printf("(%d,%d) --> code=%d\n",p2.x,p2.y,c2); getche();
    Driver = DETECT; initgraph( &Driver, &Mode, "" );
    line(p1.x,p1.y,p2.x,p2.y);
  }
  getche();
  closegraph();                 /* Return the system to text mode       */
}