On Sun, Apr 10, 2022 at 1:18 PM Noel Chiappa <jnc@mercury.lcs.mit.edu>
wrote:


> Unix had (and still may have, I'm not up on Linux, etc) a really major,
> hard
> boundary beween 'user' code, in processes,and the kernel. There are
> 'instructions' that invoke system primitives - but not too many, and
> limited
> interactions across that boundary. So, restricted semantics.
>

The same is true for the more recent Unix variants, modulo a few special
cases such as Larry mentions, but broadly speaking userland and the kernel
are still separated.

> Imagine building a
> large application which had a hard boundary across the middle of it, with
> extremely limited interactions across the boundary.
>

You mean like the Web?  :-)

In 2000-2005 I wrote a substantial quasi-batch application that supported
$EMPLOYER's main product and was written about half in shell scripts and
half in Perl, or more accurately entirely in shell scripts, but if I needed
a pipeline component that wasn't already available in SunOS or as
third-party open source, I wrote it in Perl.  (There was a single 10-line C
program to eliminate a performance bottleneck.)  So the application as a
whole was full of hard boundaries across which nothing could pass except
text streams; I found that this added substantially to its debuggability
and maintainability.