Engineers on the ground designed a way the astronauts could connect air-cleaning devices from the command module to the air system in the lunar module.

VOA: special.2009.07.22

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