RE: Entry Parameters

Based on other responses, I knew that the AS/400 could do Integer much
faster but I had always thought the AS/400 had built in support for packed
decimal arithmetic that was inherent in the hardware or MI. My response was
based on using zoned Vs packed, not on whether integer was faster than
packed. 

Hans response was that this was done for accuracy purposes only.

So question still seems open. Are you better off using packed decimal for
parameters or zoned? My understanding is packed. Zoned is something left
over from the System 36. Obviously if this was counter or some other kind of
zero precision number you would want to use integer but creates a problem
because CL does not support binary types. If you are using a command
interface, you can pass values to a RPG ILE that are binary, i.e. integer
but not to CL. 

I started using integers for my service program functions but quickly got
burned on that one when I try to call one of the functions with an integer
parameter and, of course, it blows up. 

There are ways to get around it. (Create a wrapper function for CL to accept
packed and covert to integer and call function or call a function to create
a binary value in a string and pass that(ugly!)) but what seems safer is
using packed decimal for parameters on service program functions. Anybody
got any opinion on that. 
  
Thanks.

-----Original Message-----
From: Shaw, David [mailto:dshaw@spartan.com]
Sent: Friday, January 21, 2000 6:44 AM
To: 'RPG400-L@midrange.com'
Subject: RE: Entry Parameters


-----Original Message-----
From: Alan Campin [mailto:Alan.Campin@CaseLogic.com]

Not to argue here. Maybe Hans could give use the true run down but all my
understanding in 20 years of technical journals and performance tips says
that the AS/400 is a packed decimal machine, the only one in the world. I
believe that this has been extended to allow efficient other types (Like
integer) but the native format of an AS/400 is packed decimal to the point
where the math is done in a base 10 format(for absolute precision), not base
2(Binary). In other words, the AS/400 is business data processing machine,
not a scientific machine. If you have ever had to work on a machine that
uses floating point number to represent decimal values and all the problems
inherent in that, you know what I mean. We are really spoiled on the AS/400
because we never have these kind of problems. 

Everything I have read says the AS/400 takes a zoned value, converts it to
packed decimal, does the arithmetic in Base 10 and then converts the result
back to zoned. 

----------------------------

My understanding is that the AS/400 directly supports packed decimal, zoned
decimal, integer, and floating point arithmetic.  Many of the major business
computers support decimal arithmetic without resorting to floating point -
you
don't think that S/360, S/370, and S/390 machines only do floating point and
integer, do you?  Or that business machines from Burroughs or Sperry Univac
had
that kind of disadvantage relative to IBM?  After all, the COBOL standards
specify support for decimal arithmetic in COBOL programs.  My experience is
that
the decimal arithmetic issue mainly applies to the scientific machines,
things
like VAXes and Unix boxes.

As for the implicit conversion to packed, I have read a number of times that
it's the RPG III compiler that does that, not OS/400 and not the hardware.

Dave Shaw
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