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Bill Joy on writing vi

The Register quotes a Linux Mag interview with Bill Joy on the design constraints for writing vi:

What happened is that Ken Thompson came to Berkeley and brought this broken Pascal system, and we got this summer job to fix it. While we were fixing it, we got frustrated with the editor we were using which was named ed. ed is certainly frustrating.

We got this code from a guy named George Coulouris at University College in London* called em - Editor for Mortals - since only immortals could use ed to do anything. By the way, before that summer, we could only type in uppercase. That summer we got lowercase ROMs for our terminals. It was really exciting to finally use lowercase.

So we modified em and created en. I don't know if there was an eo or an ep but finally there was ex. [laughter] I remember en but I don't know how it got to ex. So I had a terminal at home and a 300 baud modem so the cursor could move around and I just stayed up all night for a few months and wrote vi.

Linux Mag then asked: "So you didn't really write vi in one weekend like everybody says?"

No. It took a long time. It was really hard to do because you've got to remember that I was trying to make it usable over a 300 baud modem. That's also the reason you have all these funny commands. It just barely worked to use a screen editor over a modem. It was just barely fast enough. A 1200 baud modem was an upgrade. 1200 baud now is pretty slow.

9600 baud is faster than you can read. 1200 baud is way slower. So the editor was optimized so that you could edit and feel productive when it was painting slower than you could think. Now that computers are so much faster than you can think, nobody understands this anymore.

The people doing Emacs were sitting in labs at MIT with what were essentially fibre-channel links to the host, in contemporary terms. They were working on a PDP-10, which was a huge machine by comparison, with infinitely fast screens.

So they could have funny commands with the screen shimmering and all that, and meanwhile, I'm sitting at home in sort of World War II surplus housing at Berkeley with a modem and a terminal that can just barely get the cursor off the bottom line.

It was a world that is now extinct. People don't know that vi was written for a world that doesn't exist anymore - unless you decide to get a satellite phone and use it to connect to the Net at 2400 baud, in which case you'll realize that the Net is not usable at 2400 baud. It used to be perfectly usable at 1200 baud. But these days you can't use the Web at 2400 baud because the ads are 24KB.

Even now latency from (say) Australia to the US is high enough that being able to type a long way ahead in the way that vi supports is quite worthwhile.

George Coulouris writes, about vi:

The system support person (I don't recall his name, but I have a vague recollection that he went to Bell Labs later. Bill Joy might be able to tell you his name) said something like: "That's very nice, but if we made it available to all of our users the overheads associated with running in raw mode (a process swap on each key depression) would swamp the cpu".

I was rather depressed by this reaction, thinking "I guess I have been unrealistic in developing an editor that is so expensive to run - it's ok in our small system, but it's no use in the big Unix environment at Berkeley".[...]

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".

posted Mon 15 Sep 2003 in /software/people | link

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