Emacs

Emacs ( /ˈiːmæks/) is a family of text editors, characterized by their extensibility. One manual describes it as "the extensible, customizable, self-documenting, real-time display editor." Development began in the mid-1970s and continues actively as of 2012. Emacs has over 2,000 built-in commands and allows the user to combine these commands into macros to automate work, in particular with the use of Emacs Lisp, a variant of Lisp, providing a deep extension capability.