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Re: Certified C compilers for safety-critical embedded systems

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Can you explain, possibly enlightened with an example, why Pascal would be
next to useless in that interesting place where software meets hardware?

Meindert




Re: Certified C compilers for safety-critical embedded systems
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That is certifiably insane.  However I can see banning edge
triggered interrupts.
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Far from it.  The file abstraction of ISO Pascal allows almost
anything to be connected (and I have done so, from interrupts to
networks to devices).  Those file drivers are probably not going
to be written in Pascal.  This serves the function of splitting
off system dependencies very nicely, and preserves the safety
aspect of a better structured language.

Cs problems largely arise out of making it a structured assembler,
capable of coping with anything at all.

--
Chuck F ( snipped-for-privacy@yahoo.com) ( snipped-for-privacy@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
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Re: Certified C compilers for safety-critical embedded systems

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That's kinda the point ... you can't write the driver in Pascal and
thus have to give up all of the safety the language was intended to
provide.

Modula 2 sucked at bit banging although it did Pascal two better.  It
allowed "open ended" array parameters - the actual array size and
index bounds could be determined at runtime via library functions
which enabled array handling functions to be written generically.  It
also allowed data structures to be accessed as "array of word".
However, the size of a "word" was implementation dependent so this
feature was of limited value.

Modula 3, designed by DEC and having no relation to the Wirth
languages aside from some similarity of syntax, is a modern, strictly
typed, object oriented language designed for both application and
system level programming.  Modula 3 gives the programmer full access,
but in a controlled way.  Modula 3 divides the world into "safe" and
"unsafe" code.  "Safe" code does not allow pointers, can perform only
a defined "meaningful" subset of possible data conversions and is GC'd
by default.  "Unsafe" code must be segregated within a library module,
but can do pretty much anything it wants: access hardware, use
pointers, arbitrarily access memory and data structures, perform
arbitrary data conversions, bypass the GC and do custom memory
management, etc.  There are strict rules governing how data is to be
shared between "safe" and "unsafe" code.

Modula 3 is very similar to Ada without subtyping.


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Well ... C was intended to be a "portable assembler" for writing
operating systems.  That design goal required that it provide (nearly)
all the power of assembler while abstracting just far enough from the
machine to make programs easily retargetable.

No one was forced to use C for general purpose programming.  That
shift occurred  mostly because it was there, it could do what people
needed and very few good alternatives were available.  

George
==============================================
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Re: Certified C compilers for safety-critical embedded systems
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No drivers ?
Nik Wirths Pascal was indeed close to useless. Intermediate and
current implementations allow you to write drivers. Why shouldn't
they ?

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net


does anybody use a seperate marketing company?
I realize this is a little OT but I was wondering if there are
other embedded controller developers that simply create
embedded devices and then hand it over to other companies
to do the sales and marketing for them?

Steve



Re: does anybody use a seperate marketing company?

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I did something along those lines. For a number of years, I had a limited
partnership with a larger company who marketed my stuff in exchange for a
share of the profits. One problem was that no one in their orginization
understood the technology. Since my entire market consisted of engineers
and technicians with sharply tuned bullshit filters, the old "a good
salesman can sell anything" credo didn't apply. It turned out that I ended
up writing all the meat of the ad copy - to avoid explaining embarrassing
statements like "several orders of megahertz better than the competition",
went along as technical rep on most important sales calls, and handled all
technical questions and a support. After a while I started wondering what I
was paying the sales force for.

Bob

Re: does anybody use a seperate marketing company?
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I

Do you think it would make a difference if the product(s)
were being marketed to the masses as opposed to
the technical crowd?



Re: does anybody use a seperate marketing company?
oN 22-Dec-03, Steve Letkeman said:

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It might, but you're leaving yourself very vulnerable. You build up a
business and a clientele, but someone else has all the market data,
contact lists, etc.

--
Bill
Posted with XanaNews Version 1.15.8.4

Re: does anybody use a seperate marketing company?

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I've thought about that quite a bit and yes, I think a generic marketing
approach is better suited to a consumer product than an industrial or
technical one. I would recommend some sort of arrangement based on
performance, like percentage of sales, rather than a fee, and only give
exclusive marketing rights if they will guarantee a minimum number of sales
per year. Needless to say, this will weed out all but the true believers in
your product line. If you can't find an outfit willing to give you a
guarantee, which you probably can't, give them non-exclusive rights to
market your products, and incentivise(sp?) them buy discounting their cost,
and not undercutting them through your own or other sales channels.

Bob

Re: does anybody use a seperate marketing company?
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Yes, this is called being an invention house. Routine practice in some
industries (toys, for instance).

Re: does anybody use a seperate marketing company?
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Well it can't have done them any good.  When did you last see a new idea
in the toy industry?

Re: does anybody use a seperate marketing company?
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Tamagotchi and Furby come to mind. The problem is that the marketing
structure through which these new ideas must pass first bites out most
of the innovation, then forces the product to be costed-down until
it's just another blinkenlight with a 3-second speech chip.

The toy industry is full of idiots, quite frankly. Some of them are
idiots merely because they work for a large company and such companies
encourage people to rise to the level of their incompetence. Some of
them are idiots because they are blinkered. Some of them just enjoy
being in a position to reject the creative work of others. Some of
them are just in it for the perks and kickbacks provided by suppliers.

A "nameless toy company, division of a nameless enormous consumer
conglomerate" with which I'm excessively familiar routinely pays
thousands of dollars for exclusive rights to ideas simply so they
won't go to another toy company. These ideas are interred in large
metal filing cabinets and never see the light of day because they
don't fit into a product line.

Re: does anybody use a seperate marketing company?
Simon Hosie:
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What's that, then?  About a five-year period?

Now that trading cards have gone digital, well that opens up a whole new
line of non-innovation.


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So... what you're saying is that money is paid to develop a new product,
and then more money is paid to reduce that product to being essentially
the same as all the existing products?

That's certainly a familiar story.

Re: does anybody use a seperate marketing company?

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In the toy industry the norm is for the inventor to develop the toy to the
stage where it is presentable to the toy companies and as often as not the
inventor then pays to cost reduce it.

Ian


Re: does anybody use a seperate marketing company?
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Would it be fair to say that the product has to be flashy enough to be
unbuildable (cheaply) just to make the sale?  What I see is people
developing a product that has saleable merit, then once the sale is made
and they have to make it real they end up retreating to the point of
making the same thing as everybody else.

In the end, I don't think the customer values whatever it is they say
they want.

Re: Certified C compilers for safety-critical embedded systems

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You missed the point.  

We are talking about whether the syntax and semantics of a particular
language will allow certain functionality to be expressed.  The Pascal
language standard defines type rules and expression semantics which
prohibit certain operations necessary for low level programming and
does not define mechanisms for special use circumventions of those
rules.  Within the context of our discussion, Pascal can't be used to
write a driver.


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Dealing with hardware requires the ability to address memory
arbitrarily, to manipulate arbitrary bit sequences as meaningful data
and to efficiently convert data to bits and vice versa.

Pascal doesn't allow unchecked type casting.  Compilers that support
it do so as a non portable extension.

The operational equivalent of casting, called "type overlay", requires
coercion between pointer types and conversion of non pointer types to
pointers.  Pascal's type rules don't allow converting non pointer
types to pointers or mixed types in pointer expressions (except for
"nil").  There is also no standard way to obtain the address of
anything.   Compilers that support these operations do so as non
portable extensions.

Pascal's variant records alone are no help for hardware banging - you
still need the support for type overlay so you can "map" the variant
type onto the hardware buffer.  

Implementations have always provided extensions to allow low level
programming - practically since Pascal was invented - because everyone
realized it was necessary.  But those extensions are *not* Pascal and
should not be treated as if they are part of the language.

Some Pascal derivatives do have syntax and sematics that can directly
express low level functionality - Ada, Modula 3 and Oberon come to
mind - there are probably others I don't know about because Pascal is
a popular base model for new language development.


George
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Re: Certified C compilers for safety-critical embedded systems

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I think a more interesting question is: given a particular quality of
programming talent and fixed amounts of time and money, how will
software written in C fare against software written in "better" (as
determined by safety-critical industry concensus) languages?  I think
the evidence is overwhelming that it will fare quite badly, meaning it
will cost more and/or take more time and/or and have more residual
errors.

Mike

Re: Certified C compilers for safety-critical embedded systems
On 22 Dec 2003 10:20:04 -0800, snipped-for-privacy@yahoo.com (Mike Silva)

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Sounds interesting. Can you provide references to such evidence,
obtained under the stated conditions?

I'd also be interested in documentation of the ranking of languages
"as determined by safety-critical industry concensus."

--
Al Balmer
Balmer Consulting
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Re: Certified C compilers for safety-critical embedded systems
           snipped-for-privacy@spamcop.net "Alan Balmer" writes:

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The only ranking I have seen on that basis is within IEC61508.

--
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Re: Certified C compilers for safety-critical embedded systems
On Mon, 22 Dec 2003 22:46:36 +0000 (UTC), snipped-for-privacy@amleth.demon.co.uk

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Since I'm not developing safety-related systems currently, I can't
justify the money for the standard, so I'll just hope that Mr. Silva
will have another input.

--
Al Balmer
Balmer Consulting
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