I don't think vi would work correctly in cooked mode. It has to redraw (some of) the screen, inserting a character on each keystroke, and repainting the rest of the line.

As Clem points out, in V6 it used raw, in V7 it used cbreak, which is "half cooked" and allows interrupts.

It certainly affected performance when lots of students were using it, especially if they all had their own copies of the binary, which was typical on non-BSD systems. What really helped there was ensuring that the official vi binary was in /usr/ucb (or another standard directory) so that only one copy of the instruction space would be in memory, shared among all the users.

Bell Labs, which typically ran internal versions of UNIX that didn't have vi, created the exptools package with most of the Berkeley tools and certain others, such as Montgomery's EMACS. This was partly to address the performance issue, and to get people to stop installing their own personal copies of everything.

Thanks,

Mary Ann Horton (she/her/ma'am)       maryannhorton.com "This is a great book" - Monica Helms "Brave and Important" - Laura L. Engel       Available on Amazon and bn.com!

I remember being told back in the 1980s that vi would set the terminal to "cooked mode" when vi was in "insert mode", so as to reduce expensive context switching for each character typed.  Only vi's "command mode" would set the terminal to "raw mode" so as to provide immediate feedback on each (command) character typed.  This would be a clever system performance optimization, and would also explain designing vi around distinct insert and command modes.

However, I can't find such evidence even as far back as BSD 1.  It seems that in insert mode ESC was processed like any other character.

https://github.com/dspinellis/unix-history-repo/blob/BSD-1-Snapshot-Development/ex-1.1/ex_vops.c#L507

Cooked mode was only entered when scrolling in order to receive interrupts.

https://github.com/dspinellis/unix-history-repo/blob/BSD-1-Snapshot-Development/ex-1.1/ex_vadjust.c#L180

Also, for this scheme to work ESC would need to be mapped to an interrupt key, so as to allow exiting the cooked mode through the corresponding signal handler.  Again, grepping for ESC, did not show me any such code.

I also remember being told that this optimization was what allowed twenty students to concurrently perform interactive editing on a VAX 11/780 (running 4.2BSD and then 4.3BSD), and that Emacs was not provided to students because it was always operating in raw mode.

Was I misled?  Was there perhaps a hacked version of vi that worked in this way?

-Diomidis