Re: routine to translate DEC microvax Floating point...

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

Richard French <rfrench@wellesley.edu> writes:


> Hi, friends -
>     I have some 20-year old data in binary floating point format (DEC
> microvax
> running ULTRIX4.4). Unfortunately, that ancient machine, while still
> running, can
> no longer connect to the internet, so my old subterfuge of converting
> the floating
> point to ascii on the microvax, piping across the network to my Alpha
> machine,
> and then reconverting it to binary no longer works. I do have the binary
> files on
> my new machine, but I don't know how the bits are packed for DEC
> microvax
> floating point format, and my web prowls have not revealed the answer.
>     I'm hoping that some of you may know how to decode floating point
> (and possibly also double precision) from DEC microvax format to IEEE. I
> 
> think I recall seeing some IDL utilties to do this once, but I have not
> been able
> to track them down.

Hi Dick--

Why don't you simply try reading the numbers into IDL.  I did a search
on Google, and of the source code in the scientific package called
Yorick which knows about a lot of formats.  Both showed that IEEE
float and VAX float are potentially the same format, except for a
different "bias."  This suggests that reading the numbers into IDL
will give the same number, except for a factor of 2^N (which you can
determine once).

However, if you have "D" or "H" type doubles then it's harder, but
still doable.  Leaving that open-ended until you find out...

Craig

-- 
--------------------------------------------------------------------------
Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
--------------------------------------------------------------------------