Emacs

GNU Emacs is an extensible, customizable, free/libre text editor — and more.

At its core GNU Emacs is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing.

The features of GNU Emacs include: * Content-aware editing modes, including syntax coloring, for many file types; * Complete built-in documentation, including a tutorial for new users; * Full Unicode support for nearly all human scripts; * Highly customizable, using Emacs Lisp code or a graphical interface; * A wide range of functionality beyond text editing, including a project planner, mail and news reader, debugger interface, calendar, IRC client, and more; * A packaging system for downloading and installing extensions.

Android notes: * System keyboard can be invoked by tapping on a non read-only buffer; * Permissions are not granted by default, they must be explicitly enabled in system settings menu; * Android version of emacs is built without GNUTLS support