#include <graphics.h>
int getmaxwidth(void);
 

The getmaxwidth function is available in the winbgim implementation of
BGI graphics. The function returns the maximum width that will fit on the
screen when creating a window with initwindow. This is one of the few BGI
functions that may be called before calling initwindow.

/* getmaxwidth and getmaxheight example */
#include <graphics.h>
 
int main(void)
{
   /* Make a window, as big as possible */
   initwindow(getmaxwidth( ), getmaxheight( ));
 
   /* clean up */
   getch();
   closegraph();
   return 0;
}

getmaxx getwindowwidth getmaxheight initwindow

  no output of example at the moment
  do not hesitate and add it...