And for reference, incidentally, in case you ever forget what the point of some exercise was, I'll almost always comment the code up top with a quick sentence or two that reminds you what this program does.

顺便作为参考，为了避免我们可能忘记一些代码的意思，我通常会用一两个简单的句子,在上面作出注释,那样会提醒我们这个程序是干嘛的。

哈佛公开课 - 计算机科学课程节选

And then at top right there's this longer sentence to purchase new Charlie ticket, value tickets and passes, press here.

然后，右上边没有说明,怎样购买Charlie票，票值是多少,按这个按钮。

哈佛公开课 - 计算机科学课程节选