Well, my use case was to do I/O on multiple members of a PDS, using standard 
PL/I I/O. And, yes, I had to rewrite it between F and "optimizing", but that 
was a piece of cake.

It's a shame that the MVS developers didn't steal the concept of VPAM from TSS.


--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3

________________________________________
From: IBM Mainframe Discussion List [[email protected]] on behalf of 
David Crayford [[email protected]]
Sent: Friday, July 16, 2021 1:57 AM
To: [email protected]
Subject: Re: Mixing C/C++ with LE-conforming IBM HLASM

On 16/07/2021 12:20 am, Seymour J Metz wrote:
> I used to access the DCB for PL/I programs (both F and "optimizing"), but the 
> relevant interfaces are no longer documented and I'm not aware of any mapping 
> macro for, e.g., the FCB.
>
> Can you make a business case for IBM to open up the interface? If so, 
> consider a REQ or SHARE requirement.

IBM would never accept a FIT and rightly so. The FILE structure returned
by the fopen() factory function is designed to be opaque, what is called
encapsulation or information hiding in OO languages. fopen() can open
BSAM, QSAM, VSAM, z/OS Unix files and hiperspaces.
The only fields that are exposed are the read/write callback functions,
the buffer and some state information so fget() fput() etc can be
implemented using macros for optimization reasons. I dread to think why
anybody would want to poke around inside the internals of an
Abstract Data Type.

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