Re: Microsoft OS/2 -- Ideal for Ada

[martillo@bloom-beacon.UUCP]

In article <8706130340.AA00283@rand-unix.arpa> hermix!fischer@rand-unix.ARPA writes:
>Microsoft OS/2 (the replacement for MS-DOS for 286 machines) seems to have
>everything which Ada's tasking management needs, and Unix doesn't provide.

>Unlike the balky fork concept of UNIX, OS/2 treats parallel executions
>within a process as threads, which look at first glance as if they were
>designed with Ada rendezvous in mind;  the threads can share the same
>local data group, which is the opposite of UNIX fork semantics.

The correct question is whether the language implementer should
be mapping an Ada task into a Unix fork.  The Unix process is
an operating system entity which corresponds to a particular
model of computation  where user programs access a virtual machine in
isolation from all other programs and request services and request
services from the virtual machine via a generalized set of system
calls to the operating system.  Such a model makes logical i/o
and piping really trivial.  The Unix model is much more powerful
than the multics or vms model of computation.  

Now the Ada task is a programming entity which may have some use in
operating system develop and I would expect Ada tasking to compile to
processor specific tasking instructions such as are present on the
80386 or 80286 if such are present.  If such instructions are not
present, the compiler would have to simulate tasking instructions just
as a C compiler would simulate stack instructions on a machine which
had no specialized stack instructions.

Providing language level tasking by simulating non-existent tasking
instructions should be no more than a couple of days work for the
compiler writer.  The implied criticism of Unix in this article is
gratuitous and implies a lack of understanding.

>Given the apparent compatibility of Ada with OS/2, I'd like to see a discussion
>of compiler vendor plans for supporting OS/2... 

>(The only published public reference on OS/2 multiprocessing which I have
>seen at newstands is in the May 1987 Microsoft Systems Journal, pg 29 ff.)

>  Herm Fischer

I thought applications written in ADA were supposed to be portable.