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。

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Other signals move the read/write heads to read or write data on the platters.

其他的信号移动读写头,来到硬盘中去读或者写。

哈佛公开课 - 计算机科学课程节选