Emacs is the most powerful text editor available today. Unlike most other editors (in particular, unlike the standard Unix editor, vi), Emacs is a complete working environment. No matter what you do, you can start Emacs in the morning, work all day and all night, and never leave it: you can use it to edit, rename, delete, and organize files; to compile programs; to run shell commands; and so on. Before windowing systems like X and Microsoft Windows became popular, Emacs often served as a complete windowing system of its own. All you needed was a terminal, and you could live within Emacs forever. Emacs is also infinitely flexible; you can write your own commands, change the keys that are associated with commands, and (if you are willing to take the time) do just about anything you want.