[SunRescue] Re: Multics

[Greg A. Woods]

[ On Tuesday, May 22, 2001 at 12:30:39 (-0400), Michael Thompson wrote: ]
> Subject: [SunRescue] Re: Multics
>
> >Is anyone releasing the Mutlics code to public domain?  Maybe we could
> >port it to sparc.
> 
> I took care of the OS on a Honeywell mainframe running GCOS...about 30
> years ago. GCOS shares a lot of code with Multics. It was mostly assembler
> with some Fortran, Cobol, and Algol tossed in for some of the utilities.

Huh?  I don't think that's right.  All of what I ever saw of Multics was
PL/1, except for bits of ALM (AML?(sp?)) [DPS-8 assembly language].

GECOS no doubt borrowed many ideas from Multics, but if there was no
PL/1 in there then there was no actual Multics code in there.

Indeed Multics was one of the first large multi-user operating systems
written "entirely" in a high level language.  From the FAQ:

        1.3.3. High-level language implementation                               
                                                                                
    Multics was written in the PL/I language, which was, in 1965, a new         
    proposal by IBM. Only a small part of the operating system was              
    implemented in assembly language. Writing an OS in a high-level             
    language was a radical idea at the time.                                    
                                                                                
There's more interesting info in the FAQ about GCOS64 and GCOS7, some of
which hints that it was actually written in HPL (a subset of PL/1).

> Really interesting code, especially the CPU dispacher.

Hmmm...

> The security
> software was very tightly coupled to the hardware so a port to a different
> hardware platform would be difficult.

The Multics security model (rings of protection) was indeed tightly
coupled to the hardware, but the DPS-8 wasn't unique in these features
and indeed the Intel 386 has some of the same support right in the CPU.  I
don't know if modern iAPx86 processors have carried forward the same
features or not though.

Indeed VMS on the VAX uses hardware ring protection too!  :-)

-- 
							Greg A. Woods

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