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NNTP-Posting-Date: Thu, 03 Apr 2025 16:20:29 +0000
Subject: Re: Rewriting SSA. Is This A Chance For GNU/Linux?
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From: c186282 <c186282@nnada.net>
Date: Thu, 3 Apr 2025 12:20:31 -0400
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On 4/3/25 11:12 AM, David W. Hodgins wrote:
> On Thu, 03 Apr 2025 06:11:37 -0400, c186282 <c186282@nnada.net> wrote:
> <snip>
>>    You're seeing the True Picture - It's *not* "easy" to
>>    re-write at all.
>>
>>    And if you get it wrong there's all hell to pay.
>>
>>    Which is why bcrats are hyper-conservative in these
>>    regards. They have good jobs/pensions to protect.
>>
>>    IMHO, any re-write will HAVE to involve a 'parallel system'
>>    for awhile ... give it the same data, the same tasks, and
>>    eval if it's always doing the same thing as the old stuff.
>>    THEN, in a few years, quietly switch.
> 
> The problem is people come in who do not understand how many parts there 
> are or
> are willing to spend the time to learn. They look at one small part such 
> as the code
> for the main module, and think it's easy to convert.
> 
> They rush the conversion, and only after they start using the new 
> versions, learn that
> they missed or misunderstood many of the edge cases.
> 
> They then get wrong results, but insist their results are correct!
> 
> There are many languages used, not just COBOL Some of the ones I worked 
> with include
> Fortran, PL/1, RPG III, Mark IV, ADF, ASM (360/370),
> 
> Even simple looking things like MFS code for screen definitions has 
> quirks that are not
> going to be obvious to anyone who has not encountered them.
> 
> For example, in a 3270 style terminal where an input field is restricted 
> to numeric, uppercase
> letters are still allowed.
> 
> It's done that way to allow for signed numeric fields. In EBCDIC, the 
> zoned decimal value for
> minus one and the capital letter D both use the same hexadecimal value. 
> Plus one is "C".
> 
> With edge cases, the problem is that the person doing the conversion 
> doesn't understand that
> they exist, so they don't include them in test data, and don't encounter 
> them during any parallel
> testing. Later, the system fails to handle the edge cases.
> 
> Regards, Dave Hodgins



   Aww ... just give 'em a copy of "COBOL For Total Idiots"
   and it'll all be just fine  :-)

   Anyway, I do see where all those jagged little edges
   can totally confound anybody attempting conversions
   from the original sources.

   A sort of work-around is a functional understanding of
   the original - hardly ever look at the source - and then
   reproduce the function in a 'newer and better' lang/system.

   In short, GM didn't have to reproduce a Model-T, just
   have an idea of what cars were expected to do, what
   some of the parts should look kind-of look like. Then
   their own people could build a relative work-alike.

   Dealing with decades of the old RECORDS ... there's
   a pain regardless.