At 08:33 AM 12/10/2001 -0500, Bryan C. Warnock wrote:
>On Monday 10 December 2001 03:06 am, Tom Hughes wrote:
> > In message <20011210011601$[EMAIL PROTECTED]>
> >
> > "Bryan C. Warnock" <[EMAIL PROTECTED]> wrote:
> > > - Endianness. The three major types are Big, Little, and Vaxian.
> > > Supporting these three should handle the majority of cases.
> >
> > Actually VAXes have perfectly ordinary endianness - it was PDPs that
> > had the middle endian layout.
>
>Who's got the 16 bittish little endian layout ("21436587")? (Perhaps it's
>wrong to categorize that as endianness.)
The PDP-11. It's a 16-bit system, so 32-bit words are stored as a pair of
16-bit ones. Swapped accordingly. Hence the... interesting layout. ;)
> > > - Floating point representations. The four major types are IEEE(ish),
> > > Vaxian, Cray's CRI, and the IBM/370 hexadecimal format. There are some
> > > minor variations among these, particularly with how much of the
> > > IEEE-754 standard floating point operations adhere to. However,
> > > adherence falls more into Portability Layer Three, and we will solely
> > > address representation.
> >
> > Of course there are also about five variants of floating point
> > format on the VAX although only two are 64 bits in size. Some of
> > those exist (or are emulated) on Alpha as well although that also
> > has IEEE types.
> >>
> > Presumably that's G_Floating that you're converting to/from for
> > the VAX rather than D_Floating?
>
>Yes. Is that going to be a problem? (The sum of programs I've written on
>a VAX can be represented with 1 digit. In base 2.)
Don't sweat the VAX format much--just be able to read G_Floats on other
platforms. VMS boxes have library routines to convert between F, G, D, H,
S, T, and X format floats. (And Cray floats, and IBM small and large
floats, FWIW)
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
teddy bears get drunk
