Код:

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
int main(void)
{
   int gdriver = DETECT, gmode, errorcode;  /*auto detection */
   int xmax, ymax;
   initgraph(&gdriver, &gmode, "");  
   errorcode = graphresult();     
   if (errorcode != grOk)  /* an error occurred */
   {
      printf("error: %s\n", grapherrormsg(errorcode));
      printf("Press any key to halt:");
      getch();
      exit(1);
   }
   setcolor(getmaxcolor());
   xmax = getmaxx();
   ymax = getmaxy();
   line(0, 0, xmax, ymax);
   line(10,10,20,20);
   getch();
   closegraph();
   return 0;
}