An A is worth four points, a B three points, a C two points and a D one point.

VOA: special.2009.03.05

B It swaps this one and these two, A and B, but it has no access to main's memory.

它交换了这个和这两个变量，A和，但是它没有介入到main的内存中。

哈佛公开课 - 计算机科学课程节选