The command line is a text interface for your computer. It’s a program that takes in commands and passes them on to the computer’s operating system to run.

From the command line, you can navigate through files and folders on your computer, just as you would with Finder on Mac OS or Windows Explorer on Windows. The difference is that the command line is fully text-based.

The advantage of using the command line is its power. You can run programs, write scripts to automate common tasks, and combine simple commands to handle difficult tasks. All of these traits come together to make it an important programming tool.

This course is for unix-based systems such as Linux and Mac OS X. You can also download programs on Windows that will allow you to use the same commands. An appendix of all commands taught in this course is available here.


When using the command line, we refer to folders as directories. Files and directories on your computer are organized into a filesystem.

Move on to the next exercise to find out how the filesystem works.

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