STructured Editing Tool
Author: Mike Cowlishaw Wikipedia: http://en.wikipedia.org/wiki/STET_%28text_editor%29 Family: MainframeEditorFamily, IbmEditorFamily FoldingEditors Platform: VM/CMS License: Commercial
STET may have been the first folding editor.
STET was written to explore an approach to text editing that followed the principles of Structured programming. It allows programs and documentation to be written 'top-down', with blocks of code or text kept to a limited size (usually less than a page).
This was "a first attempt to take the structure out of the domain of languages, and into the domain of editors. In addition to conventional editing facilities, STET gives the user a third dimension: a tree structure that may be traversed using Program Function Keys much as scrolling is normally implemented"