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From: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu (William Thomas Wolfe, 2847 )
Newsgroups: comp.lang.misc
Subject: Re: Relationship between C and C++
Message-ID: <8459@hubcap.clemson.edu>
Date: 22 Mar 90 02:58:01 GMT
References: <D_D27L1xds13@ficc.uu.net>
Sender: news@hubcap.clemson.edu
Reply-To: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu
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From article <D_D27L1xds13@ficc.uu.net>, by peter@ficc.uu.net (Peter da Silva):
>> What is this wonderful "power" which C is giving me, which requires
>> me to live with all the pitfalls?
> 
> There are only two languages I know of in which you can take a moderately
> complex program and run it, without modification, on a wide variety of
> platforms.  One is Fortran, with the Software Tools library.  The other 
> is C... When I can take a 10 year old screen-oriented program written for 
> Version 7 UNIX and run it on an IBM-PC under MS-DOS, then take the same 
> source and compile and run it under both System V and BSD UNIX, it's going
> to take more than theoretical arguments about safety to make me change. 
> It's going to take working code.  For what other language can I get 
> compatible compilers for: UNIX, IBM-PC, Amiga, Atari ST, Macintosh,
> RSX-11/M, VAX/VMS, RMX-86?  

   Ada has validated compilers for a very wide variety of platforms,
   several hundred compilers in fact.  I doubt that the Amiga and Atari
   are among them, due to their small size, but above a certain threshold
   Ada is pretty much universally available and almost totally portable.

   Due to the no-subsets, no-supersets policy, backed up by the compiler
   validation testing requirement, Ada software is highly portable.  The
   main source of portability problems has been operating system-dependent 
   things such as screen I/O, and the preferred technique has usually been
   to isolate such things in small, well-defined packages whose package body
   (implementation) is adapted to the new environment.  But I know, you want
   total, don't-lift-a-finger portability.  Well, so does the Ada community.
   And the result has been CAIS, the Common APSE Interface Set.  There is
   now a process by which CAIS is being merged with PCTE, the European
   Portable Common Tool Environment (or words to that effect), and soon
   we will have a worldwide standard for the interface to operating system
   support facilities.  There is also a validation system for CAIS which
   (the validation system) began formal testing in December 1989 and will
   soon be released.  Combined with the Ada 9X move toward standardizing
   with respect to multinational character sets and the like, there should
   soon be a level of transportability which far exceeds that of C code.

   OK, but it's not here yet, you say... well, that's true.  But there is
   relatively little difficulty associated with porting Ada systems now,
   and in my view the code engineering benefits associated with the Ada
   language far outweigh any minor, short-term porting adaptations which
   might be associated with linking to a particular operating system's
   screen I/O facilities.  In case it's *that* important that you be able
   to not lift a finger, maybe it would indeed be best to wait a few years.
   If you want controlled studies on the performance of CAIS implementations
   on different platforms, add on a few more years.   If you want to be 
   able to get a free copy of CAIS for your machine as well, simply hold 
   your breath until one becomes available.  (Just kidding!!!)   There
   does come a point, though, at which any particular aspect such as
   level of portability has to be considered in relation to other factors
   such as amount of reduction in the length of the testing phase -- 98%
   (vs. 100%) portability, combined with a steep reduction in testing and
   maintenance costs, is probably an extremely reasonable tradeoff to make.


   Bill Wolfe, wtwolfe@hubcap.clemson.edu