By the way, ‘em’ stands for ‘editor for mortals’ – I christened it that after Ken Thompson visited our lab at QMC while I was developing it and said something like: “yeah, I’ve seen editors like that, but I don’t feel a need for them, I don’t want to see the state of the file when I’m editing”.

So I was wondering… would a line editor still be feasible today? The obvious answer is “no”, of course. Nobody uses them anymore, as far as I can tell (at least not interactively)… as a matter of fact, quite a few people seem to think that even an editor isn’t good enough to edit code anymore, they want IDEs (whatever that means — it seems to depend on the speaker).

However, I have a tendency to look for non-obvious answers. :-) Question is, why did Ken Thompson say this? Notice that this quote is from around 1975, when line editors were pretty much the default (or so I understand; I was only 2 years old at the time :-). I assume that Ken has moved on since then. Nevertheless, one can wonder, did he say that simply because he was used to line editors and didn’t see the need for anything “fancier”; or is it because line editors have certain qualities not found in other editors?

I have never really used line editors myself. In 1991 my first PC came with edlin, which seemed prehistorical even then. Heck, the C64 had a more powerful environment to code in! But I have often wondered what it would be like to use them. Because of all their restrictions, they force you to focus on only the text (or code) you are interested in. This would make for a very different editing experience than jumping through the whole documents using cursor and PgUp/PgDn/Home/End and friends.

Many questions arise:

• Would modern-day users be able to get used to it? (I have power users and hackers in mind here, people who regularly use a command line of some sort.)
• How would you get around the document (efficiently)?
• How would you copy & paste?
• How would you delete or replace stuff and be confident that it didn’t overwrite the wrong thing?
• Would it be possible to add modern features like code completion, svn integration, etc, and what would it look like?
• What would be the macro/automation capabilities of such an editor? (Probably quite powerful)

Maybe this would make for an interesting (although not necessarily practical) side project. I’m especially interested in finding out what it “feels” like to use such an editor, if it’s still usable nowadays, if it has benefits of any kind over regular editors, and if/how modern features can be added to it.