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2005 ]
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Robert Blair wrote:
> ** Reply to message from "Gregory W. Smith gsmith@well.com" on Thu, 20 Jan 2005
> 10:05:58 PST8
>
> > And what about the third set that you seem to forget: the
> > "implementation set".
>
> You don't need hardware to implement any feature.
This is getting confusing. Back on December 27 Lynn
wrote that:
---> I mention this because over on SourceForge they have a
---> project to have a PL/I pre-processor to a proposed C 4.0
---> language compiler. I have my doubts because no version of C
---> comes anywhere near the native data types of PL/I: no bit
---> strings, no non-null terminated character strings of length
---> greater than one and no variable precision real and integer,
---> binary and decimal arithmetic, no variable precision fixed and
---> floating point, decimal and binary values.
--->
---> This means that C and its current derivatives can only
---> natively express a subset of that possible in PL/I. Thus you
---> could write a C pre-processor to PL/I, but not the
---> reverse...unless you revert to assembly language. If you
---> revert to assembly language you will not have a C language,
---> but a hybrid.
So, you don't need hardware to do a feature, but you can't do a
feature if it isn't native to the software? Strange. ;-)
> > For a long time, very few people bought
> > machines that did decimal arithmetic. I know that my fist OS/2
> > machine did not have decimal arithmetic--binary only.
>
> All of the INTEL chips (8080, 186, 286, and 386) that I have written assembler
> programs for had decimal hardware.
I completely forgot about the DAA instruction on the 8080. Things tend to
get away from you if you don't do it for twenty years. My quick scan of
the Intel documents led me to believe that the BCD capabilities of the
Pentium series were part of the FPU. I just assumed that chips prior to
the 486 didn't have BCD since the 8087 was an add-on option.
--
Gregory W. Smith (WD9GAY) gsmith@well.com
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