Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!snorkelwacker!ai-lab!rice-chex!bson
From: bson@rice-chex.ai.mit.edu (Jan Brittenson)
Newsgroups: comp.sys.handhelds
Subject: Re: RPL constructs
Message-ID: <11423@life.ai.mit.edu>
Date: 17 Oct 90 20:55:12 GMT
References: <11408@life.ai.mit.edu> <9206@helios.TAMU.EDU>
Sender: news@ai.mit.edu
Organization: nil
Lines: 51

In article <9206@helios.TAMU.EDU> 
   n233dk@tamuts.tamu.edu (Rick Grevelle) writes:

 > I not quite sure what it is that you're asking; 

   Perhaps I should have been more precise: this may dumbfound you,
but all I want to know is how they are stored. I remember someone
mentioning a while ago that there is more to how an IF clause is
stored than just the keywords (RPL addresses of IF, THEN, etc). I have
also noticed there are several more branch (switch on types, for
instance) instructions used internally.

 >> Oh, and could someone explain what reals (i.e. 64-bit floating point
 >> words) look like? Things like how the exponent is stored, the exponent
 >> sign, the mantissa sign, etc. I haven't done any thorough
 >> investigation here, and only know vaguely what is what.

 > Alonzo Gariepy explains this in his Processor Notes in terms of the
 > various fields used within the internal registers.  Here is a
 > simplification of it.

 >
 >                         Internal Real
 >                 
 >                    s mmmmmmmmmmmm s ee ppppp

 >iii) The two lower case e's are the exponent.

   Is the exponent stored as an 8-bit integer (i.e. 0-255), or as two
digits (00-99)? It would make sense to me if also bits of the exponent
sign nibble were used, since the exponent range is -499 to 500.
Perhaps it's three digits (000-999), with a xsn digit of '5' or higher
denoting negation? What about the mantissa sign - are mantissa signs
of 0-4 considered positive while 5-9 are considered negative?

 > Whoa!  I don't know about this; it could be a potential copy right
 > violation.  ...HP is a rather large and powerful corporation, with
 > high dollar attorneys on retainer.  Posting, without permission,
 > portions of code from the 48's ROM on which HP holds the copyright is
 > a very grey area.

   If this is a problem, I can volunteer to set up a mailing list to
which I only add people after they submit me a message stating their
48's serial number, and its place and date of purchase. I'll be more
careful with posting things like this to the net.

 > Personally, I'm little paranoid about much of the material alluded to
 > in my postings.  I am almost certain that by now HP must hate me.

   Does HP even care? If nothing else, it's probably just good for
their sales and image.