[Info-vax] Creating an open source version of VMS, was: Re: OpenVMS Hobbyist Notification

[Arne Vajhøj]

On 3/11/2020 9:33 AM, Simon Clubley wrote:
> On 2020-03-10, Arne Vajhøj <arne at vajhoej.dk> wrote:
>> It would look like VMS, but because of all the
>> "improvements" then a lot of existing VMS stuff would
>> not run as expected.
> 
> That depends on how much existing VMS application code bypasses the
> documented APIs and tries using the private/undocumented memory
> locations and functions.

They don't even need to use that any private/undocumented for
your approach to break things.

Trivial example:
* COM file use F$GETJPI to retrieve PID and create a file with
   that in file name
* COM file run EXE
* EXE use LIB$GETJPI to retrieve PID and read the file

Both F$GETJPI and LIB$GETJPI are public well documented,
but if you change DCL from running EXE in same process to
run in different process, then the above stop working.

>> It makes sense to have VMS be VMS.
>>
>> It makes sense to create something new.
>>
>> But something that is mostly but not fully
>> VMS I do not see any demand for.
> 
> People said that about Linux in the early days when comparing it to Unix...
> 
>> It will be like demand for an almost C
>> compiler.
> 
> In the same way that Linux was an almost Unix when it started ?

I see very few similarities with that situation.

One VMS vs something VMS like is different from a dozen
different but similar Unix vs something Unix like.

A VMS that has seen very little progress for
a couple of decades and users that do not want
big changes (because if they did then they would
have moved off VMS) is different from the rapidly
evolving Unixes back then.

Arne