The erythrina tree grows with it's annual rings added, the rings remember how the world change and record what have been changed, But it can not remember or record the changes in man's brain. That is the reason why we must do it by ourselves, show it ourselves, record it ourselves, remember it ourselves, and that's the reason why we use pens, why we use paper, why we use computer, why we use disk...A nice lad from here China. Hope we can be friends.