# Scrolling and Parallax scrolling in 2D game

I'm developing a 2D side-scrolling game.I have a scrollable bitmap for background with size 2400x480.How can i scroll this bitmap?I have searched for algorithms but i can't find any solution.

I know that i can do it with following code:

for(int i=0;i<100;i++)
draw(bitmap,2400*i,480);


So it will scroll bitmap for 240000 pixels.

But i don't want to draw images which stays out of screen(with size 800x480).

How can i render scrolling tile?How can i give velocity to it?(For parallax scrolling after normal scrolling)