all bits zero?

[bdm659 at csc.anu.oz]

In article <1217 at sdrc.UUCP>, scjones at sdrc.UUCP (Larry Jones) writes:
> In article <2108 at gmdzi.UUCP>, wittig at gmdzi.UUCP (Georg Wittig) writes:
>> Does ANSI C require that in the internal representation of the integer constant
>> ``0'' all bits are zero?
>
> ANSI C requires a pure binary numeration system for all integral
> types, so "yes".
[... and similar answers from lots of other people]

I think you are all wrong.  The implementation must only behave *as if*
integral types are represented in binary.  Integers might in fact be
stored in packed-decimal or something; if conforming programs can't
tell the difference, it doesn't matter.  Such an implementation is
going to have to work hard to do bitwise operations, for example, but
that's not the issue.

I think the correct answer to the original question is:  "Zero can be
stored any way the compiler-writer felt like it.  However, you won't
be able to write an ANSI-conforming program which can tell that it isn't
stored in binary with all bits zero."

Brendan McKay.   bdm at anucsd.oz.au  or  bdm659 at csc1.anu.oz.au