Page 0 was Re: [Gllug] BBC and acorn bits

[Richard Jones]

On Sun, Nov 26, 2006 at 03:20:39PM +0000, Andrew Black wrote:
> Page 0 having registers looks like a recipe for registers accidently 
> getting corrupted (eg a pointer set to 0 or a low value).
> I am most familiar with the VAX and Alpha architecture where the lowest 
> page is always (at least under VMS) no access.  I have many times been 
> saved by processes access violating rather than overwritting data and 
> plowing on regardless.

You have to remember that on 8 bit machines it would be very
unusual[1] indeed to use a C-like high-level language.  Most
programming was done in machine code without an assembler, and
less-than-serious programming in BASIC, and neither of those have
NULL-pointer concerns.  Your machine code program either runs or it
crashes ...  BASIC of that era doesn't have pointers at all.

Rich.

[1] I do have a book in my attic where they use C to program a PCW
8256 (or all things) running CP/M and GSX.  In the book they actually
point out how certain unspecified issues with the Z80 make C run very
inefficiently.

--  
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
Internet Marketing and AdWords courses - http://merjis.com/courses - NEW!
Merjis blog - http://blog.merjis.com - NEW!
-------------- next part --------------
-- 
Gllug mailing list  -  Gllug at gllug.org.uk
http://lists.gllug.org.uk/mailman/listinfo/gllug