They were really gray and there's this heavy feeling in the air,

黑压压的一片，空气中有种厚重的感觉，

I wonder if 实战 - SpeakingMax英语口语达人

Some programs won't stop until you're old and gray. And these are really different efficiencies, and we want to give you a sense of how do you reason about those different kinds of programs.

头发花白之前是不会停的,这些是因为它们的效率不同,我们想要给你们理解,这些程序之所以,表现不同的原因。

麻省理工公开课 - 计算机科学及编程导论课程节选