You put it between two pieces of paper, then you write on the top one and it creates as copy on the bottom one.

你将它放在两张纸之间，然后你在上面那张纸上写字,下面那张纸上就会复印下来。

耶鲁公开课 - 金融市场课程节选

So Jordan, playing the role of human is going to type or write something down on this piece of paper, GetInt hand it back to, get int.

所以Jordan，担任人类的角色，键入,或者在这张纸上写下点东西，把它传给。

哈佛公开课 - 计算机科学课程节选