man SCREEN_W () - Global define to obtain the size of the screen. Allegro game programming library.
NAME
SCREEN_W, SCREEN_H - Global define to obtain the size of the screen. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
#define SCREEN_W;
#define SCREEN_H;
DESCRIPTION
Global defines that return the width and height of the screen, or zero if the screen has not been initialised yet. Example:
char buf[100];
...
uszprintf(buf, sizeof(buf),
"The screen size is %d x %d pixels",
SCREEN_W, SCREEN_H);