This is the Simple DirectMedia Layer, a general API that provides low level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL, and 2D framebuffer across multiple platforms. This code is a compatibility layer; it provides a binary and source compatible API for programs written against SDL 1.2, but it uses SDL 2.0 behind the scenes. If you are writing new code, please target SDL 2.0 directly and do not use this layer.