https://doc.cat-v.org/bell_labs/sam_lang_tutorial/sam_tut.pd...

Also interesting, with other derivates of ed -- LineEditorFamily in the TextEditors Wiki: https://texteditors.org/cgi-bin/wiki.pl?LineEditorFamily

  > ed isn’t quite flipping binary toggle switches to load your program, but close enough to deliver the joy of brutal minimalism along with a nostalgic waft of yesteryear.

ED is, well, miserable. It’s a character editor, vs a line editor, and you had the joys of paging in chunks of your file into working memory.

I, personally, find command line character editors especially difficult. I find it very hard to maintain my context and, of course, who doesn’t just love counting characters for commands.

But if you're totally comfortable with vim you'd better use ex, which basically is both an extension to ed, and the non-interactive part of vim.