is_windowed_mode - Tells if you are running in windowed mode. Allegro game programming library.

       This function can be used to detect whether or not set_gfx_mode() selected a windowed mode. Example:

          if (set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0) != 0)
             abort_on_error("Couldn't set graphic mode!");
          if (is_windowed_mode()) {
             /* Windowed mode stuff. */
          } else {
             /* Fullscreen mode stuff. */
          }

       is_windowed_mode - Tells if you are running in windowed mode. Allegro game programming library.

       Returns  true  if  the  current graphics mode is a windowed mode, or zero if it is a fullscreen mode. You
       should not call this function if you are not in graphics mode.

set_gfx_mode(3alleg4)

Allegro                                           version 4.4.3                        is_windowed_mode(3alleg4)

#include<allegro.h>intis_windowed_mode(void);