Now, in the world of Linux and Unix more generally, both of which are our operating systems that had been around for many, many years, Mac OS is based on one of-- one version thereof.

在Linux和Unix里更广泛，对了，这两个都是历史悠久的,操作系统，就连Mac操作系统,都是基于它的一个版本设计出来的。

哈佛公开课 - 计算机科学课程节选

It turns out on a Linux system there's this command called "man" for manual page.

结果是在一个Linux系统中，这里有这样一个叫做“man“的命令,用来显示指南手册的。

哈佛公开课 - 计算机科学课程节选