man allegro_404_char () - Character used when Allegro cannot find a glyph.
NAME
allegro_404_char - Character used when Allegro cannot find a glyph.
SYNOPSIS
#include <allegro.h>
extern int allegro_404_char;
DESCRIPTION
When Allegro cannot find a glyph it needs in a font, it will instead output the character given in allegro_404_char. By default, this is set to the caret symbol, `^', but you can change this global to use any other character instead. Example:
/* Show unknown glyphs with an asterisk. */ allegro_404_char = '*';