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IEEE Standard 754 floating point number [message #4210]

Sun, 14 May 1995 00:00

bso
Messages: 3
Registered: May 1995

Junior Member

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I'm using the Macintosh version of IDL that supports 32-bit floats and 64-bit
double precision floats. I need to read some 80-bit IEEE Standard 754 floats
from a binary file. If I read those 10 bytes with a READU into a BYTARR(10),
how do I get a floating-point value out of that byte array?

Bosco So | bso@acm.org
PGP public key | http://www.ultranet.com/~bso/pgp/

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Re: IEEE Standard 754 floating point number [message #4274 is a reply to message #4210]

Thu, 18 May 1995 00:00

lmudge
Messages: 9
Registered: October 1994

Junior Member

In article 1405951400220001@bso.tiac.net, bso@acm.org (Bosco Y. So) writes:
> -----BEGIN PGP SIGNED MESSAGE-----
>
>
> I'm using the Macintosh version of IDL that supports 32-bit floats and 64-bit
> double precision floats. I need to read some 80-bit IEEE Standard 754 floats
> from a binary file. If I read those 10 bytes with a READU into a BYTARR(10),
> how do I get a floating-point value out of that byte array?
>
> Bosco So | bso@acm.org
> PGP public key | http://www.ultranet.com/~bso/pgp/>

The most obvious option would be to use IDL's bolean algebra capabilities
(e.g. not or and ishift etc.) to create a routine that converts this data to
a double precision value. This would result in a loss of precision because
this is only 64 bit IEEE floating point. The next version of IDL (v4.0)
will support double precision complex data type which you could also
use to store your values in but you would need to create your own
routine to perform basic operations on this data e.g. addition. This is
probablly not feasible.

On a brighter note I have written a routine to convert values read from
Turbo Pascal files using the word data type (16 bit unsigned integers) to
IDL longword variables. If anyone would like it send me email.

Leith Mudge.

------------------------------------------------------------ --------------------
Leith Mudge
lmudge@awadi.com.au
AWA Defence Industries
PO Box 161
Elizabeth SA 5112
Australia
Phone: +61 8 256 0952
Fax: +61 8 255 9117

Microsoft Network is prohibited from redistributing this work in any form,
in whole or in part. Copyright, Leith Mudge, 1995
License to distribute this post is available to Microsoft for $1000.
Posting without permission constitutes an agreement to these terms.

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