E is a text editor originally developed at the Stanford AI Lab (Stanford University) in the 1970s for the Twenex and TENEX operating systems. E was one of the first WYSIWYG editors of the 1970s. Richard Stallman visited the Stanford Artificial Intelligence Lab in 1976 and was quite impressed by the feature. He implemented a similar hack to the TECO text editor once he returned to MIT in adding a combined display+editing mode called "Control-R"[1]