SDL Video Surface

OK, my question is, is the surface returned by SDL_SetVideoMode() just a
backbuffer? I guess it must be since either a Flip(), or UpdateRect() is
required to view the updated frame.

The reason I ask is I’d like to write my own blitting routines,
specifically, alpha blended blitting, and this would require alot of
reading and writing to the backbuffer.

Thanks for any information you can give me.