So I figured out how to draw a bitmap in mode 13, hooray! Now I'm trying to make a sprite(another bitmap) move around on my loaded bitmap background. I think I know how I want to do it and here's the general idea:

1.Draw the background to screen buffer
2.Draw the sprite over it
3.Transfer screen buffer to video memory for output

Now here comes the tricky part for me. As the sprite moves around my background I don't want to constantly redraw the entire image. I just want it to redraw the sprite and just the portion of the background that it moves over. Or is there another easier way to avoid having to redraw what the sprite moves over?