ZWEI was an early (~1980s) Emacs

Emacs

Emacs is a class of text editors, usually characterized by their extensibility. GNU Emacs has over 1,000 commands. It also allows the user to combine these commands into macros to automate work.Development began in the mid-1970s and continues actively...

-like text editor

Text editor

A text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....

 written by Daniel Weinreb

Daniel Weinreb

Daniel L. Weinreb is a programmer and computer scientist. He attended MIT 1975–1979, graduating with a B.S. in Computer Science and Electrical Engineering, where he wrote EINE, the text editor for the MIT Lisp Machine. EINE made use of the window system of the Lisp Machine, and thus is the first...

 and Mike McMahon

Mike McMahon

Michael McMahon or Mike McMahon may refer to:* Michael McMahon , Democratic Congressman for New York's 13th Congressional District* Michael McMahon Michael McMahon or Mike McMahon may refer to:* Michael McMahon (born 1957), Democratic Congressman for New York's 13th Congressional District* Michael...

for the Lisp machine

Lisp machine

Lisp machines were general-purpose computers designed to efficiently run Lisp as their main software language. In a sense, they were the first commercial single-user workstations...

. It is the successor of the editor EINE

EINE

EINE was the Emacs text editor for Lisp machines. It was developed by Daniel Weinreb and Mike McMahon in the late 1970s, with a command set the same as the original Emacs written in TECO by Richard Stallman...

 (which means a/one as in "a/one woman" in German). Innovations by it include programmability in Lisp

Lisp programming language

Lisp is a family of computer programming languages with a long history and a distinctive, fully parenthesized syntax. Originally specified in 1958, Lisp is the second-oldest high-level programming language in widespread use today; only Fortran is older...

, and a new and more flexible method of internally representing

Data structure

In computer science, a data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently.Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks...

 buffers. It would later become Symbolics

Symbolics

Symbolics refers to two companies: now-defunct computer manufacturer Symbolics, Inc., and a privately held company that acquired the assets of the former company and continues to sell and maintain the Open Genera Lisp system and the Macsyma computer algebra system.The symbolics.com domain was...

' editor of choice for its Lisp machine development environment, Zmacs

Zmacs

Zmacs is one of the many variants of the Emacs text editor. Zmacs was written for the MIT Lisp machine and runs on its descendants . Zmacs is written in Lisp Machine Lisp...

. ZWEI sources are available online http://www.heeltoe.com/retro/mit/mit_cadr_lmss.html.