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's a little more involved on a PC but it's all free, the software you can download, and Linux in similar operating systems generally come with a compiler or you run a simple command to get it.

在PC机上有点复杂，但是它是免费的，你一般下载的软件，类似Linux的操作系统等等通常都需要,一个编译器，或者你可以运行一些简单的指令来获取。

哈佛公开课 - 计算机科学课程节选