Editing Incompatible Timesharing System (section)

==Important applications developed on ITS==
The [[Emacs|EMACS]] ("Editor MACroS") editor was originally written on ITS. In its ITS instantiation it was a collection of [[TECO (text editor)|TECO]] programs (called "macros"). On later operating systems, it was written in the common language of those systems – for example, the [[C language]] under [[Unix]], and [[Zetalisp]] under the [[Lisp Machine]] system.

[[GNU]]‘s [[Info (Unix)|info]] help system was originally an EMACS subsystem, and then was later written as a complete standalone system for Unix-like machines.

Several important programming languages and systems were developed on ITS, including [[Maclisp|MacLisp]] (the precursor of Zetalisp and [[Common Lisp]]), [[Micro-Planner (programming language)|Microplanner]] (implemented in MacLisp), [[MDL programming language|MDL]] (which became the basis of [[Infocom]]'s programming environment), and [[Scheme (programming language)|Scheme]].

Among other significant and influential software subsystems developed on ITS, the [[Macsyma]] symbolic algebra system, started in 1968, was the first widely-known mathematical computing environment. It was a forerunner of [[Maxima (software)|Maxima]], [[MATLAB]], [[Wolfram Mathematica]], and many other [[List of computer algebra systems|computer algebra systems]].

[[Terry Winograd]]'s natural-language interpreter [[SHRDLU]] was developed on ITS. The computer game ''[[Zork]]'' was also originally written on ITS.{{Citation needed|date=February 2025}}

[[Richard Greenblatt (programmer)|Richard Greenblatt]]'s Mac Hack VI was the top-rated chess program for years{{Citation needed|date=April 2019}} and was the first to display a graphical board representation.{{Citation needed|date=April 2019}}