Re: Advantages

[Marin David Condic <nobody@noplace.com>]

I'm not sure what you want for statistical proof. In my experience with 
writing low-level software in an environment where I don't have an OS, I 
can say that the things that tend to cause the most difficult problems 
are where the software meets the hardware. Try to get two different CPUs 
synchronized across some communication link or deal with some I/O device 
where timing or synchronization are important to getting it right. Or 
sometimes its within the CPU instruction set itself - where arguments 
start about hardware vs software bugs. The *hard* stuff to get right is 
not related to bugs in type checking or constraint checking (or other 
language related stuff). Its the uncertainty of when things are 
happening or the fact that dozens of things are happening nearly all at 
once and corner conditions can come up that are difficult to test and 
difficult to program around.

Tasking may help, but that is only built on the assumption that your 
tasking primitives down at the low level have no bugs. Try figuring out 
how to synchronize tasks across multiple processors and implement the 
full set of Ada requirements in that regard and it might give you an 
idea of how difficult that might be to get right.

So I don't think that Ada automagically makes an OS "better" in some 
regard. Its going to have more to do with how sound the "Model" is for 
the lower level stuff - and even then, as you pile more and more layers 
on top ofit, you start discovering the limitations or design flaws in 
the model. I'm not saying someone can't do a better job with Ada - just 
that an OS is *really hard* to make stable and secure and it isn't 
something that can be done in a few weekends of coding and hope it will 
somehow be better.

MDC

Andrew Carroll wrote:
>>------------------------------
>>Message: 6
>>From: "Nick Roberts" <nick.roberts@acm.org>
>>Subject: Improving Ada's Image
>>
>>"Marin David Condic" <nobody@noplace.com> wrote in message
>>news:40CEDEBB.3050209@noplace.com...
>>
>>
>>>Like I said: The thing that makes operating systems hard to
>>>get right are not usually language issues. They are related to
>>>the asynchronicity of events and the complexity of the
>>>algorithms involved.
>>
>>This is one of the biggest advantages of writing system software in
> 
> Ada.
> 
>>Quite a lot of the really nasty pitfalls associated with parallel
>>programming in other languages are made either impossible or much more
>>easily detected and debugged by Ada.
> 
> 
> Okay Marin and Nick, I want to learn more.  Where can I find the
> statistical and practical proof?  I'm not trying to snub your comments,
> I just want to be able to provide the proof when I talk to my co-workers
> about Ada.  Thanks!
> 
> 


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Marin David Condic
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