[Info-vax] VMS documentation, was: Re: Special deals on Tape Drives

[VAXman- at SendSpamHere.ORG]

In article <622cf1b9$0$703$14726298 at news.sunsite.dk>, =?UTF-8?Q?Arne_Vajh=c3=b8j?= <arne at vajhoej.dk> writes:
>On 3/12/2022 1:53 PM, Simon Clubley wrote:
>> I don't know what Bill found to be confusing, but I can see some people
>> being confused by all the VMS-specific stuff such as a way over-complex
>> descriptor system,
>
>The use of descriptors is hidden for those programming in enough high
>level languages: Pascal, Fortran, Cobol, Basic etc.. It can hardly
>get any simpler than that.
>
>Those programming in and Macro-32 need to know that they are sending
>over type, length and address. Not particular complex. If they can't
>grasp that concept then I don't think they will get far on those
>languages.

        CLRL    -(SP)                           ;dynamic; dsc$a_pointer
        PUSHL   #<DSC$K_CLASS_D@<DSC$B_CLASS at TOBITS>>!- ; dsc$b_class
                 <DSC$K_DTYPE_T@<DSC$B_DTYPE at TOBITS>>   ; dsc$b_type

I just build dynamic descriptors on the stack and let VMS allocate for
me the storage for the data.



>OK. There is an ugly side to descriptors - when one goes outside
>simple fixed length or variable length strings, then it can become
>tricky. But that is extremely rare and usually only happens
>for some advanced language interop problems.

There a uniform definition for myriad generic structures that descriptors
entail beyond simple strings, but Simon just likes to hear himself bitch
and believes we want to as well.



>>                     as well as the fact the documentation needs to be
>> written at a lower level than with the Unix documentation to deal with
>> all the exposed structures that in Unix are hidden behind call interfaces,
>> C structs, etc.
>
>There is nothing low level in sending over complex structures instead
>of simple data types. Almost all modern API's does that (it is just
>called an object!).

;)

Simon isn't happy unless it's littered with lots of "squigglies", typedefs,
and other C eunuchisms.

-- 
VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG

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