So we left off last time with looking at a bit of coding and teasing you with the upcoming problem set.

我们上次讲到了查看一些代码,并且给你们带来这下面的习题。

哈佛公开课 - 计算机科学课程节选

You can say if this is true, then go and do the following pieces of code or puzzle pieces that are inside this part of the block, else go ahead and do these that are down here.

你可以说如果条件成立，执行下面的代码段,或板块中的拼图，否则跳过去执行这下面的语句。

哈佛公开课 - 计算机科学课程节选

OK, let me comment this out, and let's look at this next little piece of code. All right.

好，让我添加一点注释，然后让我们看看,下面的一些代码，好。

麻省理工公开课 - 计算机科学及编程导论课程节选

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