QED is a powerful, programmable and extensible text editor with a CLI interface. Just as Emacs had multiple from-scratch implementations by different authors, s

QED is a powerful, programmable and extensible text editor with a CLI interface. Just as Emacs had multiple from-scratch implementations by different authors, so did QED. The Tilbrook, Pike, Redelmeier QED for Unix was based on the ed source code. It was far more powerful than vi (also derived from ed), but lacked vi's visual mode. The CLI interface allows you to perform global text transformations across a collection of files, using short 1 line commands. It's a very powerful paradigm, not really duplicated in either Emacs or in mainstream editors. Rob Pike's 'Sam' editor is a successor to QED with more powerful regular expressions, and a visual editing mode. I knew David, and I was amazed at how productive he was using qed.