Or where should I save the screenshot to if I'm too lazy to make a dialog for selecting the location?
You could use getenv("HOME") to get the path to the user's home directory, then append /Desktop to save the file to their desktop. E.g.
char OutputBuffer; //arbitrary big number
sprintf(OutputBuffer, "%s/Desktop/%s", getenv("HOME"), filename_for_file);
Also, of the built in formats provided by Allegro, BMP is the smartest choice for saving as it is supported by all the tools the OS comes with and will be capable of being previewed in the Finder (i.e. using a small version of the image as the icon - much as XP does).
Arrow left/right: Change the fractal resolution
Ah, I hadn't figured these two out, and...
Combination of +/- on the numeric keypad and W, A, S, D: Resizes the field. For example, if you press + and W, this will make more tiles on the left.
I'm on a laptop so I don't really have a numeric keypad, although I can do the keypresses with "fn" shifts and so on...
If you're still modifying, I'd also add a set_close_button_callback! I can't remember what happens under XP with Allegro, but if you don't use that in Allegro the program window still has a red close button it just annoyingly doesn't do anything.