Emacs

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Emacs is a family of text editors known for being highly customizable and extensible. The most widely used version is GNU Emacs, described as an extensible, customizable, self-documenting, real‑time display editor. The project started in the mid‑1970s, and GNU Emacs (version 30.2 as of August 14, 2025) is still actively developed.

Key ideas about Emacs:
- It has thousands of built‑in commands and lets you combine them into macros to automate tasks.
- Emacs uses a Lisp-based extension language called Emacs Lisp (Elisp). The core is in C, and most features are built or extended with Lisp code.
- People write extensions to handle files, email, Git, RSS, remote access, and even playful programs and games.

A quick history:
- The original EMACS (Editing MACroS) started in 1976 at MIT as macros for the TECO editor.
- Richard Stallman began GNU Emacs in 1984 to create a free alternative to Gosling Emacs; the first public GNU Emacs release was in 1985.
- XEmacs branched off from GNU Emacs in 1991; it diverged in development and is much slower today.

How Emacs works:
- Text is edited in buffers. Buffers are shown inside windows, which sit in frames (the main GUI windows). You can have many frames and many windows showing the same buffer in different ways.
- Commands run from keystrokes, and you can redefine keys or run Lisp code directly.
- A universal argument button lets you change how commands run, often by prefixing a number to repeat actions or change behavior (for example, inserting more characters or performing a reverse action).

Major ideas in the editor:
- Major modes customize Emacs for a type of work (like editing a particular programming language) and set the available commands. Minor modes add extra features that you can toggle on or off.
- Emacs can run as a background editing server, letting other programs connect to it. This makes it behave a bit like a shared editing service across different tools or sessions.

Learning and help:
- Emacs is self-documenting: most commands have help text, and you can jump to the code that defines them. It also includes a built‑in tutorial to get new users started.

Culture and other notes:
- Emacs is one of the oldest free, open‑source editors still in use. It has sparked friendly rivalries with other editors, most famously vi.
- There are playful communities around Emacs, such as the Church of Emacs, a humorous take on editor culture.
- The word emacs is sometimes pluralized as emacsen to refer to different Emacs variants.