Re: Why couldn't an operating system be written in ada

[Norman Worth <nworth@comcastNOSPAM.net>]

lyttlec wrote:
> On 2/26/19 4:30 AM, Dmitry A. Kazakov wrote:
>> On 2019-02-26 09:46, Niklas Holsti wrote:
>>> On 19-02-25 23:56 , Rabican wrote:
>>>> On Saturday, July 13, 1996 at 3:00:00 AM UTC-4, Mark  McKinney wrote:
>>>>> It has been claimed that the capability to interface with other
>>>>> languages
>>>>> is a great asset to ada. Sometimes interfacing can be a tremendous
>>>>> liability. Besides the OS could perform most of work that the language
>>>>> runtime does. So why not build an OS in ADA?
>>>>
>>>> yeah why not?  anything?
>>>
>>> This has been discussed many times before in comp.lang.ada.
>>>
>>> The first question is not "why not build an OS is Ada", the first
>>> question is "why build a new OS at all"?
>>>
>>> Then, if a new OS is going to be built for some reason, we can ask
>>> which language should be used, and of course (IMO) Ada would be a
>>> strong contender. However, for larger systems, the OS must usually
>>> implement a "process" concept that goes beyond Ada tasking and
>>> provides isolation between different users and applications. This
>>> means that the OS will have a process/service-level API that is not,
>>> as such, Ada-language specific. And so the fact that the OS is
>>> implemented in Ada becomes invisible on the application level.
>>>
>>> This is not to say that an OS API specified in Ada could not be an
>>> improvement (for Ada applications) on the current OS APIs which are
>>> usually specified in C. However, such an Ada OS API could also be
>>> provided for an OS implemented in C or some other language.
>>
>> Right. This is a general problem only tangentially related to Ada. The
>> purely procedural OS API outlived their time.
>>
>> A new generation of OSes must have higher-level API which would include
>> tasking and synchronization primitives as well as other abstract types
>> types. Call it OO or not, but that is beyond procedures, ints and void *.
>>
>> The world is not ready for this and the languages, Ada included, are not
>> mature enough either.
>>
>> So, yes, one can write an C-esque OS in Ada, but who needs yet another
>> horse cart?
>>
> Often overlooked is that any "C-esque" POSIX compliant OS turns the
> computer into a VAX. C was written to be easily translated into VAX
> machine code and POSIX signals are all the original interrupts on a VAX.
> If you have a CISC computer running VMS, C is your language.
> 
Actually, C was written for the PDP-6, long before the VAX.  It was used 
at AT&T to write UNIX for that machine, long before VMS.