Let's take a quick glimpse of what it's like to write a real program albeit a very trivial one.

下面是一个真正的程序,尽管它很简单。

哈佛公开课 - 计算机科学课程节选

I am going to run a program called Nano nano hello c and type nano hello.c and I'm gonna type the following very quickly without much explanation because we'll dive into this more next week.

我要运行一个Nano程序,键入,我快速写下下面的内容,不打算做过多的解释,因为下周我们会深入了解这些。

哈佛公开课 - 计算机科学课程节选

But notice what this does. The first thing it does is, it says, let's check and make sure x is greater than or equal to 0. If it isn't, notice what's going to happen. None of that block is going to get executed, and it's going to come down here and print out a useful piece of information, which says, hey, you gave me a negative number. I don't know how to do this.

做的是和以前一样的事情,但是注释它做了什么，第一件做的事情就是,程序说，要去检查并且确信x是大于等于0的，如果不是的话，请注意会发生什么,下面的代码都不会被执行,程序会到这里来然后显示一些有用的信息,信息会说，嘿，你给了我一个负数,我不知道该怎么弄这个了。

麻省理工公开课 - 计算机科学及编程导论课程节选