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From: gwinn@res.ray.com (Joe Gwinn)
Subject: Re: ada and robots
Date: 1997/06/10
Message-ID: <gwinn-1006971907100001@dh5055139.res.ray.com>#1/1
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References: <338CDA96.53EA@halcyon.com> <338F5D7D.6C03@tiac.net>
 <338F9D05.5EB3@bix.com> <5mqpj3$bc5$1@goanna.cs.rmit.edu.au>
 <33930245.12A1@sprintmail.com> <5mv984$7kn@news.emi.com>
 <gwinn-0306971836410001@smc19.ed.ray.com> <dewar.865941342@merv>
Organization: Raytheon Electronic Systems
Newsgroups: comp.robotics.misc,comp.lang.ada
Date: 1997-06-10T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.865941342@merv>, dewar@merv.cs.nyu.edu (Robert Dewar) wrote:

> Joe said
> 
> <<In practice, C was much more successful than Ada83 at riding metal. 
> Experience with Ada83 shows that it is very bad at direct control of
> hardware, especially I/O hardware, and simply does not handle shared
> memory correctly.>>
> 
> Please explain this claim. Please post sample code that you think is
> defined in C and handles shared memory correctly ...

There is tons of such code available for free on the internet.  Just look
for I/O drivers, such as for UNIX and VxWorks. VxWorks Board Support
Packages are another example.  

Even C-coded I/O drivers and kernel initialization sequences resort to
some assembly code.  

As for shared memory, look into the handling of driver comm pools, queues
shared between tasks and also with ISRs.  And so on.

For UNIX drivers, there are multiple books available on exactly how to
write such drivers, all in C.  Most include (annotated) sample driver
code.  

I would submit that there is ample evidence that C can be used for direct
hardware control, and for shared memory.  

I would not claim that all who have tried such things have succeeded,
regardless of language.  Many programmers couldn't write an I/O driver if
their life depended on it.


Joe Gwinn