#include <graphics.h>	
#include <stdlib.h>	
#include <stdio.h>	
#include <conio.h>	
#include <math.h>	
// this function initializes graphics mode	
// it will work only if you're using Borland C++ compiler & BGI drivers	
// if you're using another compiler you should overwrite body of this function	
void init_gr(void)	
{	
   /* request autodetection */	
   int gdriver = DETECT, gmode, errorcode;	
   /* initialize graphics mode */	
   initgraph(&gdriver, &gmode, "");	
   /* read result of initialization */	
   errorcode = graphresult();	
   if (errorcode != grOk)    /* an error occurred */	
   {	
       printf("Graphics error: %s\n", grapherrormsg(errorcode));	
       printf("Press any key to halt:");	
       getch();	
       exit(1);               /* return with error code */	
   }	
}	
// this function shuts graphics mode down	
// it will work only if you're using Borland C++ compiler & BGI drivers	
// if you're using another compiler you should overwrite body of this function	
void end_gr(void)	
{	
  closegraph();	
}	
// this function puts pixel on the screen in (x,y) position using color 'color'	
// it will work only if you're using Borland C++ compiler & BGI drivers	
// if you're using another compiler you should overwrite body of this function	
void PutPixel(int x, int y, int color)	
{	
  putpixel(x,y,color);	
}	
void BLine(int x1,int y1,int x2, int y2, int color)	
{	
  int delta_x,delta_y,incx,incy,t,distance;	
  int xerr=0,yerr=0;	
  // determine dx and dy	
  delta_x=x2-x1;	
  delta_y=y2-y1;	
  // determine steps by x and y axes (it will be +1 if we move in forward	
  // direction and -1 if we move in backward direction	
  if (delta_x>0) incx=1;	
  else if (delta_x==0) incx=0;	
  else incx=-1;	
  if (delta_y>0) incy=1;	
  else if (delta_y==0) incy=0;	
  else incy=-1;	
  delta_x=abs(delta_x);	
  delta_y=abs(delta_y);	
  // select largest from deltas and use it as a main distance	
  if (delta_x>delta_y) distance=delta_x;	
  else distance=delta_y;	
  for (t=0;t<=distance+1;t++)	
  {	
    PutPixel(x1,y1,color);	
    // increasing error	
    xerr+=delta_x;	
    yerr+=delta_y;	
    // if error is too big then we should decrease it by changing	
    // coordinates of the next plotting point to make it closer	
    // to the true line	
    if(xerr>distance)	
    {	
      xerr-=distance;	
      x1+=incx;	
    }	
    if (yerr>distance)	
    {	
      yerr-=distance;	
      y1+=incy;	
    }	
  }	
}	
int main(void)	
{	
  // initializing graphics mode	
  init_gr();	
  /* examples */	
  BLine(0, 0, 640, 480,15);	
  BLine(320, 0, 320, 480,10);	
  BLine(0, 240, 640, 240,11);	
  BLine(0, 480, 640, 0,12);	
  BLine(320, 11, 10, 5,13);	
  BLine(320, 11, 630, 5,13);	
  /* clean up */	
  getch();	
  end_gr();	
 
  return 0;	
}