So what would I want to do? I'd like to somehow walk down each of the digits one at a time and add them up. Ah, that's a looping mechanism, right? I need to have some way of walking through them.

去取这个数的,每个数字然后把他们加起来,啊，这是个循环机制对不对？,我得找到一个遍历它们的方法,一种简单的方法可能。

麻省理工公开课 - 计算机科学及编程导论课程节选