A Brief Glance at How Various Text Editors Manage Their Textual Data (2015)
> [Sam] is one of the first editors to separate its UI from the actual editor - Sam can be used on both the command-line and as a graphical text editor.Not even close to the first.  TECO had both command-line and graphical editing in, ah, 1964: https://en.wikipedia.org/wiki/TECO_(text_editor)#History