Re: Class Notes for a PL/I Course.

Hi Peppe,

thanks a lot for posting this link, great fun :-)

somewhere in the Paper I found the Checkout compiler mentioned;
in fact, the Optimizing and the Checkout Compiler were two Compilers that,
AFAIK, followed PL/1 (F) and were very successful products.

Some years ago I did some tests with PL/1 (F), simply to find out how 
much it differs
from today's standards.

What annoyed me most: it cannot compile definitions like

DCL VARX DEC FIXED (15) BASED (ADDR(VARY));

that is, a variable BASED on the ADDR of another variable. This coding 
is omnipresent in
our sources; I had to replace this by

DCL PVARY PTR;
PVARY = ADDR (VARY);
DCL VARX DEC FIXED (15) BASED (PVARY);

BASED in PL/1 (F) supports only pointers, no ADDR expressions.

I also checked the format of descriptors of parameters, when passing 
strings etc.;
I tried to call ASSEMBLER and FORTRAN subroutines from PL/1 (F) and to 
evaluate
the PL/1 descriptors in the called functions. I was successful in the 
end, although the
format of the descriptors is different from today's format.

To summarize: I believe most of the topics mentioned in the paper are 
present in
PL/1 (F) with minor restrictions; the definition of the language from, 
say, 1964,
contained all the features mentioned in this 1975 paper, but, maybe, 
PL/1 (F)
failed to implement some of those features properly. The Optimizer and the
Checker did much better. From time to time, I run some examples programs
on PL/1 (F) to see if a certain feature was already present there.

Some interesting example, not known to many of today's PL/1 people:

it is possible to omit the name of a component of a structure, if it is not
used, and use a star instead ... no need to invent FILLER names (many 
use F1, F2, F3 etc.)
(What is FILLER in COBOL is simply a star in PL/1). Although I did PL/1 
teaching for
many years, I didn't know this for a long time. Then I saw this coding 
in a very old
paper, and of course, even today's compilers support this:

Example:

DCL 1 STRUCTA,
 ????? 5 NAME? ? ? ? CHAR (25),
 ????? 5 ADDRESS ? ? CHAR (25),
 ????? 5 *?? ? ? ? ? CHAR (10),??? /* Offsets 50 to 59 not used */
 ????? 5 POSTBOX ? ? CHAR (10);

This was already possible with PL/1 (F).

Kind regards

Bernd


Am 03.10.2019 um 09:55 schrieb Giuseppe Vitillaro giuseppe-yuD/ahkh7LvrZ44/[email protected] 
[H390-MVS]:
>
> Wondering how much this Argonne National Lab
> PL/I Course, by Kenneth W. Dritz (Nov 1975)
>
> https://www.osti.gov/servlets/purl/7150488/
>
> is far from the PL/I F we have on board
> under MVS3.8j (TK4- or Moseley SYSCPK volume).
>
> From a first look, compared with IBM manuals,
> it doesn't seem really far.
>
> Probably is a slightly lower version? For OS/VS1?
>
> Peppe.
>
>