[Info-vax] Whither VMS?

[Jordi Guillaumes i Pons]

En/na glen herrmannsfeldt ha escrit:

>  
> < And one of the first languages that I used that had this "length byte"
> < concept was UCSD-Pascal.  Which, from the very start, included a way
> < to violate those bounds.  Go figure....
> 
> PL/I also usually uses length at the beginning.  
> 

Yup! Only for VARYING CHAR variables. On the other hand, it uses 
descriptors to pass string parameters so the called procedure knows the 
length of the incoming string, being it fixed-length or varying.

Of course, when you declare a VAR CHAR(1024) the compiler allocates 1026 
(or 1028 in the last versions) bytes, unless you declare a BASED or 
CONTROLLED variable. It's unvaluable processing varying length records:

DCL BUFFER_AREA		CHAR(1024) VARYING;
DCL 01 RECORD_TYPE_1	BASED(ADDR(BUFFER_AREA)),
        03 LENGTH        BINARY FIXED(15),
        03 DATA,
  	  05 RECORDTYPE CHAR(2),
           05...

DCL 01 RECORD_TYPE_2	BASED(ADDR(BUFFER_AREA)),
        03 LENGTH        BINARY FIXED(15),
        03 DATA,
  	  05 RECORDTYPE CHAR(2),
           05...

The more recent versions support C-isms like UNION, so the need to do 
such idioms (when you have to debug a program where one structure is 
based on the address of the last byte of another structure, which is 
based on a record, which is based on a POINTER, using a DUMP, you start 
to wonder what in #¢¢$@ was thinking the programmer about... ;)).

Oh, by the way, I'm talking about zOS PLI compilers. I've not followed 
the current status of the Kednos version vs. the last IBM PLI extensions.

(After my golden VAX days, I spent nearly 12 years coding & designing 
applications for MVS-OS/390-z/OS, in PLI and against IMS/DB/DC...).