And you might say, wait a minute, isn't that a string, and the answer's no, I didn't say it's a string by putting quotes around it And notice how the machine responds differently to it.

你会想，等等，这不是个字符串么？,答案是否定的，我没用引号包围它就意味着它不是字符串,请注意计算机对它给出了不同的反应。

麻省理工公开课 - 计算机科学及编程导论课程节选