so that在引导目的状语和结果状语从句中分别解释为什么?

so...that是表示“如此……以至于”,这是表示结果的,如：
He ate so much that he couldn't move a bit.他吃了这么多,以至于动都动不了.
so that连在一起表目的,从句中通常要有个情态动词,如：
I got up half an hour earlier than usual,so that I can catch the first bus.我早起了半小时,以赶上早班公车.