OT: Requesting C advice
hlhowell at pacbell.net
Thu May 24 01:36:03 UTC 2007
On Wed, 2007-05-23 at 18:45 -0500, Michael Hennebry wrote:
> On Wed, 23 May 2007, Mike McCarty wrote:
> > Michael Hennebry wrote:
> > > On Wed, 23 May 2007, George Arseneault wrote:
> > >
> > >
> > >>Now the bad news... C, C++, gnu, several variations on
> > >>the ISO; not to mention all the libraries, etc. And,
> > >>to top it off, some of the stuff in the book just
> > >>doesn't work. (A program to demonstrate the various
> > >>types of integer variables and how to display them
> > >>with printf(), failed to show any difference with any
> > >>arguments I could find.)
> > >
> > >
> > > Should they have produced different results?
> > On big-endian machines, they can. For example, with two's complement
> > arithmetic on a big-endian machine,
> > printf("%d\n",-2);
> > does not result in
> > -2
> It should.
> printf, declared or not, will look for an int and get it.
> printf("%u\n", -2);
> is more interesting.
> We might be in the domain of nasal demons.
> printf("%u\n", (unsigned)-2);
> Is legal, but rather obviously will not print "-2\n".
> It will probably print something even regardless of endianness.
> > > Printing (int)sizeof(typename) will distinguish some types.
> > > Note that short, int and long usually only have two distinct sizes.
> > > It's allowed, but rare, for all the arithmetic types to have size 1.
> > Note that what you suggest works because sizeof(.) for integer
> > types is going to be a small number. The only portable means
> For small read <=16.
> > of displaying an unsigned integer of unknown size is
> > printf("Thing = %ul\n",(unsigned long int)Thing);
> > For "rare" read "no known implementation". Since long int
> > is required to be at least 32 bits, that would require
> > that char be at least 32 bits.
> And double has to be more.
> My recollection is that there was a
> Cray compiler that had 64-bit chars.
> Anyone know for sure?
> Mike hennebry at web.cs.ndsu.NoDak.edu
> "Horse guts never lie." -- Cherek Bear-Shoulders
sizeof generally returns size in bytes or words (depending on how the
implementer read the spec) I have never seen it return words.
And the Cray stored 8 characters in 64 bits using ASCII coding a
LONG time ago. I had forgotten about that. I think that was the model
where you sat on the processing unit when you were at the console.
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