VMS vs. UNIX file system

[Michael I. Bushnell]

In article <68850 at sun.uucp>, guy at gorodish (Guy Harris) writes:
>> I wouldn't be at all shocked to see DEC announce (essentially) RMS
>> under Ultrix (and I'll bet a dollar someone is working on this.) Fine
>> idea, as long as it's not in the OS.
>
>Or, more precisely, not in a more-privileged mode than user mode; I consider
>the OS to be more than just the kernel - for instance, I consider UNIX standard
>I/O to be part of the OS.

But standard I/O runs in user mode, not in a more-priviledged mode.  What
you consider the OS to be is not what it in fact is.  A good working 
description of OS is that part of the system which the arbitrary user
cannot rewrite and use in lieu of the distributed code.  You can rewrite
stdio, and then not use the distributed one.  This definition is
*very* closely linked to what privilege mode the code runs in...if it
runs in user mode, the user could replace it.

>Under RSX-11, if I remember correctly, RMS is just a library that runs in user
>mode; VMS decided to fill another much-needed gap by running it in executive
>mode.  Neither of them stuffed it into the kernel, at least....

But...the user can't necessarily replace RMS without getting to write
his own CHME dispatch table, something the kernel is not likely to let
him do.
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