hpux man page for xrootwindow

XRootWindow*()															    XRootWindow*()

Name
  XRootWindow, XRootWindowOfScreen, RootWindow, RootWindowOfScreen - return root window ID.

Synopsis
  Window XRootWindow(display, screen_number)
	   Display *display;
	   int screen_number;
  Window XRootWindowOfScreen(screen)
	   Screen *screen;

Arguments
  display   Specifies a connection to an X server; returned from XOpenDisplay().

  screen_number
	    Specifies the appropriate screen number on the host server.

  screen    Specifies the appropriate Screen structure.

Returns
  The window ID.

Description
  XRootWindow()  and  XRootWindowOfScreen()  return the root window of the specified screen.  The only difference between them is their argu-
  ments.  These are useful as arguments of functions that need a drawable of a particular screen (such as  XCreatePixmap()  or	XCreateGC()),
  and for creating top-level windows.

  The C language macros RootWindow() and RootWindowOfScreen() are equivalent and slightly more efficient.

See Also
  XDefaultRootWindow*().

Xlib - Macro Equivalents													    XRootWindow*()