So what's nice if you configure your command line environment appropriately is that things that are so-called executable, programs that you wrote like a.out happened to show up as green.

只要合理设置一下命令行环境,就可以看到，这些所谓的，执行文件,譬如a，out啊等，都会变成绿色。

哈佛公开课 - 计算机科学课程节选