[Info-vax] Access to _all_ VMS system services and library functions from DCL ?

[David Froble]

Simon Clubley wrote:
> On 2017-07-11, David Froble <davef at tsoft-inc.com> wrote:
>> Simon Clubley wrote:
>>> On 2017-07-10, David Froble <davef at tsoft-inc.com> wrote:
>>>> Well, not just for DCL.  Have defined blocks of data for each system service. 
>>>> Either I allocate the memory, (probably best) or have the system service 
>>>> allocate the memory.  Then jam it full of all data provided by that system 
>>>> service.  Sure would do away with item lists, at least to some extent.
>>>>
>>> A single block of data which is directly accessed is too limiting and
>>> will cause massive maintainence problems as structures are changed and
>>> field sizes changed in the future.
>> Why?
>>
> 
> Because existing binaries will now be looking at the wrong locations
> for the data items they need.

Not if the system service rejects an improper data block.

>>> This will lead to a different version of the data block for every
>>> change in the future and all these versions would have to be kept
>>> around in the future as well as the code to populate them.
>> Why?
>>
> 
> Because it is expected that you are able to run existing user mode
> applications unchanged on the upcoming versions of an operating system.

Only if you worship at the 100% compatibility alter.  Which as Steve has 
mentioned, stifles new capabilities.  Face it, if you want to be able to 
improve, then sometimes there is a price to be paid.  If you don't want 
improvements, run your current version of the OS forever.