Portable OS's (was: Re: Do OS's slow down with age?)

[Don Stokes, Govt Print, Wellington]

In article <978 at riddle.UUCP>, domo at riddle.UUCP (Dominic Dunlop) writes:
> This approach actually works well enough to be used in the real world: UCSD
> Pascal is implemented this way, so is Pick.  (There's even a British
> product called BOS which, in effect, implements a COBOL engine, and has an
> operating system written in... you guessed... COBOL.)  The disadvantage of
> the approach is that, as the operating system and all applications are, in
> effect, interpreted by the emulator, performance is unlikely to be as good
> as could be obtained from programs compiled all the way down to the native
> machine code of the target processor.

Yeah, fine, if you want a fraction of the performance ... (fond memories 
of UCSD Pascal on Apple ][s ... <yawn>... gimme 6502 assembler anytime...).

You mention Pick ... on many implementations, Pick is actually run as 
native code.  The first phase of compilation produces something akin to 
Pcode, that code is either used directly by an interpreter, or is further 
"compiled" to produce native files.  I don't know a lot about pick, so 
I'm not sure of the details.  And Pick is almost as much of a mess as 
Unix, with every man & his dog producing different and subtly 
incompatible versions ...

Don Stokes
Systems Programmmer, Government Printing Office, Wellington, New Zealand
------------------------------------------------------------------------
Experience is directly proportional to the number of compilations plus
dumps squared.