Re: Using API's ? -- RPG400-L

Scott,

I think using qsysinc is something you do if you are interested in 
following "best practices".  For a good description of why this is 
considered best practices look in the system api programming 
manual.  It doesn't mean you have to do it, it is just best.  If I were 
developing software for internal use I might not take the extra few 
minutes, but I think overall the use of these structures saves time.  
For an idea of what can, and has changed, scan qsysinc for the 
value *$A.  You will see hundreds of changes have been made 
over the years.  In most cases new formats or fields have been 
added so as to not affect existing programs.  That is not always 
the case.

I do wish that IBM offered more flexibility in their design.  For example 
they could support versioning that was smarter than the current 
format implementation.  They could also allow you to use the structures 
without allocating storage and offer support for variable size data.

David Morris



>>> "Scott Klement" <infosys@klements.com> 09/09/99 04:19PM >>>
Eric,
      If IBM changed the parameters, or the layout of a data struct,
programs would stop working when you upgraded to the new release.
Its true that if you had used QSYSINC, its POSSIBLE that all you'd
have to do is recompile the program to make it work.  But not really
CERTAIN...

However:
      1) You can't use header files in CL programs, so any CL program
          using an API would need to be changed anyway.
      2) There aren't header files for the Unix-type APIs, so if they
          changed these, you'd have a problem anyway.
      3) In most of the APIs IBM uses a "format" code and a data
          structure so they can change the API without screwing up
          backwards compatability.

I've got lots of programs that survived the conversion from V3R1 to
V3R2 that didn't use QSYSINC.

So, I guess I'm wondering why you're making this statement?   Did it
really happen to you?  If so, I'd be very interested in the specifics!
WHAT did they change, and in WHICH API?!




"Eric N. Wilson" <doulos1@home.com> wrote:
> I have learned my lesson about creating my own headers for API's, I
>  will
> give you a hint "DON'T EVEN THINK ABOUT IT". Early on in the
>  development of
> APIs on the AS/400 (V3R1???) IBM had the fields to a certain API
>  defined one
> way then on the next release certain very important fields changed
>  their
> lengths/types. Now I know that that is not to ever happen again but
>  just to
> be safe I will continue to ?COPY QSysInc/QRPGLESRC,xxxxx just safer
>  all
> around.
>
> ______________________________________________
> Eric N. Wilson
> President
> Doulos Software & Computer Services
> 2913 N Alder St
> Tacoma WA 98407

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