It's the text editor used by Joy, Thompson and Ritchie.

?

Could you be a little more precise, please ?

Have you ever used ed? Try to actually use it for a few and you'll get it.

One good thing about ed is that it's always on even the most minimal system recovery disks (which often lack vi, even). I've been stuck using it a couple times while fixing dying systems. No fun, but better than nothing.

Actually I use a line-oriented text editor. I prefer using it because it makes me write shorter code, and I can't slack off five minutes because I'd forget the contents of the file.

Which? I'm only familiar with ed and ex.

It's one I wrote.