Weird things, bad things can happen and so one of the lessons too that will be repeated throughout the course is to actually rigorously error check and make sure that you're always thinking about your user being a bad guy.

各种古怪的事情就会蜂拥而至,所以在这个课程中我反复强调,要一丝不苟地检查错误,你就当你的用户是个调皮捣蛋的家伙。

哈佛公开课 - 计算机科学课程节选

Notice in this program I have not checked whether or not the user actually provided input.

就拿这个程序说事吧，我们根本没有检查,用户到底有没有输入。

哈佛公开课 - 计算机科学课程节选

But when you start writing programs, especially when we get to web-based stuff where you want -- to check the user's input -- is it valid, is it an email address, -- and all these different scenarios -- it's actually often useful to be able to just enumerate them or rattle them off using this switching construct instead.

但是当你看是写程序时，特别是当我们,使用基于网络的东西，你想要,检查用户的输入-,它是合法的吗？它是不是一个电子邮箱地址？,所有的这些场景-,实际上它常常是有用的，当你用枚举结构列举它们,或者用它来快速地来说出它们。

哈佛公开课 - 计算机科学课程节选

I probably whip out a do while loop very rarely, but very often when programming games or any program that takes user input and has to check that user input and yell at the user if they're messing with you or aren't providing what's expected.

我可能很少用do，while，循环，但常常是,当编制程序游戏或需要用户输入的程序是,需要检查用户的输入并提醒用户,如果他们干扰了你,或没有提供所期望的输入。

哈佛公开课 - 计算机科学课程节选