Allegro is a game programming library for C/C++ developers distributed freely, supporting the following platforms: Unix (Linux, FreeBSD, etc.), Windows, OS X, iOS, and Android.
Simple DirectMedia Layer (SDL) is a cross-platform, free and open source multimedia library
"I d strongly recommend to go with allegro 5.1.x it s a little bit more difficult than sfml but very functional and easier than sdl it s got nice support and it s compatible with plenty of os"
from question "How difficult is it to switch libraries from C++/SFML to C++/SDL"
"I was also looking at sdl allegro sfml i didnt see much tutorials help on this but heard its better than sdl"
from question "Game programming ~ SDL / Allegro / SFML / or a game engine"