Emacs Lisp

Emacs Lisp is a dialect of the Lisp programming language developed especially to write the editing functionality of the Emacs text editor (the rest of Emacs and its interpreter are written in C)

Emacs is endlessly customizable to anyone with a basic knowledge of Emacs Lisp. In particular, variables and functions setting the behaviour and appearance of the text editor can be created or modified

The language is well documented

Graphical display