emacs

GNU Emacs is a real‑time, self‑documenting text editor that can be extended and customized through Emacs Lisp. It provides a command‑line interface and a graphical display, supporting editing, browsing, and interaction with many file types. The source tree includes the core C implementation, the Lisp libraries that implement most functionality, and input‑method support for international characters.

The distribution contains build scripts (configure, makefile templates) and documentation (Info manuals, tutorials, reference guides) to help users compile and install the editor on a wide range of operating systems, including Unix‑like systems, Windows, and macOS. Developers can contribute patches, report bugs via the mailing list, and use provided scripts to create and tarballs.

Emacs is released under a free/libre license, is considered stable, and is intended for programmers, writers, and other users who need a highly configurable editing environment that can be adapted through Lisp code and external modules.