TEACL is a fork of TECOC created for the purpose of describing diffs in a document being collaboratively edited
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TEACL is the YAAPS fork of the TECOC editor

The purpose of this fork is to rewrite TECO as the back end of a collaborative text editor implemented as an Activity Pub service

TEACL - Text Editing And Collaboration Language

TEACL is a fork of TECOC. TECOC because I need a character based text editor. Fork because my use runs contrary to the stated purpose of the main repository

TEACL is not intended for human consumption. It intended to be generated in a specialized Activity Pub client for embedding in the object property of client to server activities with the media type "application/x-teacl"

The remainder of this document is about TECOC


Teco is a text editor written by Dan Murphy in 1962. It differs from other editors in several ways as follows:

Character oriented

Vi and Emacs are screen oriented editors. You view the text on the whole window or screen, and you edit the text right where you see it. Changes take affect immediately.

ed, ex, edlin are line oriented editors. Edited text is viewed, referenced, and edited by line.

Teco is character oriented. This means the unit of reference is a single character. On one hand, this may make teco cumbersome to use, but on the other hand, it gives teco very fine control over what is happening.

Teco does have a video mode, however text is still edited with commands on a character basis. The screen is simply updated once a command is completed to give the user a visual representation of where they are. Text is not edited in the screen view area.


In general, vi, ed, and edlin are not programmable. This means you have the functions the editor provides and that is all you can do. However, teco is highly programmable. Programs that you write are called macros. In fact, the original version of Emacs was written as teco macros. Also, "emacs" actually means "Editing Macros".


The original versions of Teco were written in the machine languages of the machines they operated on. As newer machines and editors arose, teco fell into increasing disuse and obscurity.

In the early '80's Pete Siemsen, a long-time teco user, created a portable version of Teco in the C language called "tecoc". Rather than create a new editor, Pete's goal was to duplicate the original teco as closely as possible.

As time wore on, Tom Almy, Blake McBride, and others increasingly assisted in tecoc's maintenance (porting, bug fixes, etc.). Eventually, tecoc found a new home and principal support at Tom Almy's home page where Tom kept up with ports to Windows, Mac, and Linux.

Most recently, Blake McBride:

  1. Merged Tom Almy's various ports along with work done by Blake
  2. renewed the Windows, Mac, and Linux ports
  3. re-enabled video support (on Mac & Linux)
  4. bug fixes and speed improvements
  5. tested on 64 bit machines

This latest work is available on github at:


Other documents in the "doc" directory provide complete documentation. See the following files in the "doc" directory:

File Description
BUILD.txt Build and setup instructions
INTRO.txt Introduction to using tecoc
teco-manual.txt Complete manual