And what happens if you want to move back and forth between a bunch of different letters?

如果你想阅读,不同的书信呢？

耶鲁公开课 - 新约课程节选

Good question, so there is this little reading head kind of like in an old phonograph player that does move back and forth and in and out depending on the implementation.

好问题，这就像,老留声机里的小读头,它通过来回移动,来完成不同的操作。

哈佛公开课 - 计算机科学课程节选