Re: A Simplified Number System

From: LEE Sau Dan (danlee_at_informatik.uni-freiburg.de)
Date: 11/02/04 

Date: 02 Nov 2004 20:10:37 +0800

>>>>> "Sean" == Sean O'Leathlobhair <jwlawler@yahoo.com> writes:

>> Not as odd as German "halb zehn" to mean half past _nine_.
>> But again, once you're used to it, you begin generating those
>> odd utterance yourself.
 
    Sean> That confused me at first.

No me. I knew this from the very beginning and hence was very careful
with it. At the beginning, whenever I heard a time expression like
that, I remind myself that it is something that I have to interpret
very carefully.

After some time, I don't have problems understanding and using it
myself. Moreover, when some people (sometimes including Germans)
translate it wrongly, I can point it out. This is important when you
have joined a local tour and the guide/translator is announcing the
gathering time (after some free activity) wrongly.

    Sean> Someone suggested 9. Since it was late and I had travelled
    Sean> far, I preferred a later start and said (in German): "Half
    Sean> nine". Someone else said: "Yes it would be a good idea to
    Sean> start earlier". I realised my mistake but it was hard to
    Sean> correct it at that point.

"Nein, Ich meinte neun Uhr dreißig." would be my reaction.

    Sean> So I got less sleep rather than more. I have not made the
    Sean> mistake again.

A reasonable price for a good lesson! :)

 
    Sean> What are your "fixed point numbers"? The ones most familiar
    Sean> to me are BCD.

Fixed point is as opposed to floating point. Recall that a floating
point number consists of 2 (signed) parts: mantissa and exponent.
With fixed point, I mean the exponent is always fixed. So, you only
need to store the mantissa. The exponent is implicit. You would of
course use exponents that are (negative) powers of 10 for financial
applications. A reasonable way to represent the mantissa in binary is
to use 2's complement form.

As a variation, you can break the number into the integral part and
fractional part, and store them using the most appropriate
representation that suits your applications.

    Sean> Working in cents would be a good technique but it is not
    Sean> popular among any financial programmers that I have met.
    Sean> Business orientated computers (mainframes and others)
    Sean> usually have good support for BCD and typically implement it
    Sean> in hardware. Look at Cobol, BCD numbers are the norm and a
    Sean> special option is required to select binary or floating
    Sean> point.

Even for NEW business-oriented computers? I doubt.

It's true that COBOL and BCD are very common on those legecay systems
built in the 60s or 70s. For younger systems, I doubt.

 
    Sean> BCD is not the only solution but it is a popular one.

Legacy systems.

    Sean> They have been called "legacy systems" for a long time but
    Sean> they do not seem to be going away.

I interpret that term as systems that use old (and inelegant)
technology but are there to stay forever. ;)

    Sean> Of course I do not know your bank balance or even your bank.
    Sean> But I have seen many banking systems and banking networks.

I have not worked in banks. So, I have never got the opportunity to
receive that confidential information.

    Sean> Sometimes these are called "scaled integers". I like them
    Sean> and believe that they are a good solution to the problem.

Yeah!

    Sean> Nonetheless they are not common in big systems.

Bigger systems: bigger momentum --> more difficult to adopt new technologies.
   

-- 
Lee Sau Dan                     李守敦                          ~{@nJX6X~}
E-mail: danlee@informatik.uni-freiburg.de
Home page: http://www.informatik.uni-freiburg.de/~danlee

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  • Re: A Simplified Number System
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