segmented memory models

[Patrick Finnegan]

On Monday 04 August 2008, Sean Conner wrote:
> It was thus said that the Great Tony Duell once stated:
> >
> > > will offend someone.  I think Intel putting them at the bottom
> > > sounds like a fine design, at least in the '70s.  'C' and it's
> > > desire to have address 0 be NULL was not around on the micros,
> > > and putting it at the
> >
> > I wasn't aware that this was a requirement of C, or any other
> > language.
>
>   The C Standard say the token "0" (in a pointer context) is to be
> translated to a null address in the target architecture, and in most
> implementations, that address is indeed 0, but it doesn't have to be.

C also does not require that the value of a pointer be the actual 
address stored by the pointer.  You could have said that the actual 
address is the value of the pointer minus 2^31 (or 2^15, 2^19 or 
whatever).

In any case, C does not require that the physical/logical address "0" is 
equivalent to NULL, only that the value of a pointer is NULL if its 
value is "0".

Pat
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