[Info-vax] Fortran problem with QIO

[glen herrmannsfeldt]

gerry77 at no.spam.mail.com wrote:
> On Wed, 2 Dec 2009 05:54:25 -0800 (PST), Steven Schweda
> <sms.antinode at gmail.com> wrote:
 
>>    Not I.  There is some C code in UnZip ([.vms]vms.c) which
>> uses QIO[W] with IO$_CREATE.  It probably does things which
>> you don't need, but it might give you some ideas.
(snip) 
 
> It was my understanding that the %DESCR built-in function was always good
> whenever there was something to pass "by descriptor". Now I'm starting to
> think that that is correct only if "something" is a character string and not
> something else. Am I right? I'm just perusing $DSCDEF in FORSYSDEF.TLB and
> I'm wondering about its contents and what I have to pass to $QIO[W]...

I remember Fortran programs doing QIO from 1979, the first time I
saw %VAL() used.  

%DESCR() should be used when call by descriptor is needed.  For
Fortran 77 that will usually be just CHARACTER variables.
For Fortran 90 and later, assumed shape arrays should also be passed
by descriptor.  Also, arrays in PL/I.

-- glen