You'll have to register, but there's no cost. At the website you'll also get a hint about areas to watch for breakthroughs in the coming year, including America's human spaceflight program.

VOA: standard.2009.12.24

So if you archive it, that's maybe a little hint that either this is just your habit or perhaps that you might actually care about this later in the future, whereas if you delete it, no, you really don't care. Yeah.

如果你把邮件存档，可能暗示这可能,是你的习惯,或者以后还会用到它，相反，如果你删除了它，说明你可能根本不在意这个邮件。

哈佛公开课 - 计算机科学课程节选

I've added the ability to have more complex data structures here. But I dropped a hint in the first lecture about what you could computer with things. In fact if you think for a second about that list, you could ask what can I compute with just that set of constructs?

我添加了使用更复杂的数据结构的能力,但是我在第一节课给大家了了一个,关于你可以用什么来做计算的暗示,实际上如果你思考,这个列表一会儿的话,你会问我可以用？

麻省理工公开课 - 计算机科学及编程导论课程节选