On May 24, 2005, at 8:12 PM, Steve Comstock wrote:
Joe Zitzelberger wrote:
On May 24, 2005, at 10:40 AM, Jon Brock wrote:
I can guarantee that the majority of our application programmers
would not know it is possible. And that includes the good ones.
[snip]
I find that amazingly unbelievable.
Learning how to invoke separate compile units is usually taught in
basic-intro-to-programming-101 classes somewhere after providing
output to the user ("hello world, my name is variable") and before
opening a file.
Humor me. Take this snippet to some of your COBOL programmers, good
and bad, and ask them if they can write a program that will invoke
it.
----------------------------
IDENTIFICATION DIVISION.
PROGRAM-ID. PGMRTEST.
ENVIRONMENT DIVISION.
DATA DIVISION.
LINKAGE SECTION.
01 INPUT-PARMS.
05 INPUT-PARM-LEN BINARY PIC S9(4).
05 INPUT-PARM-DATA OCCURS 0 TO 100 DEPENDING
INPUT-PARM-LEN PIC X.
PROCEDURE DIVISION USING INPUT-PARMS.
IF INPUT-PARM-LEN > 0
DISPLAY 'Application programmers are not really that
stupid after all.'
ELSE
DISPLAY 'OK, maybe they are really stupid.'
END-IF
GOBACK.
-----------------------------
You might find yourself surprised at how capable they can be.
I suspect that even the 'bad' ones will be able to invoke this with
ease, without using 'EXEC PGM='.
I doubt it. You get 'em with the word "invoke". And besides,
that wasn't the point being made. The point was most COBOL
programmers do not know you can get parm data from a main
program.
Kind regards,
-Steve Comstock
The original point was that "an application programmer writing in
COBOL...should not know it is possible for programs to be invoked by
anything other than EXEC PGM=". Considering the prevalence of the CALL
statement in common COBOL usage, that claim cannot be valid. There are
may ways, other than "EXEC PGM=", for a program to receive control --
and programmers know it.
However, "Invoke" is also a valid COBOL keyword for invoking methods
-AND- a commonly used generic for "handing-control-to-something" among
programmers trained in more than one language.
I can't really answer your 'main program' comment because there is no
such thing in the z/OS COBOL world. There is nothing special that
distinguishes a "main" program from any other program. If a program
can be invoked via JCL it can be invoked via call. The parms, as shown
above, can easily be identical for either JCL or call, and there is no
special way for a callee to know how it was invoked.
There is an odd, unusual, COBOL keyword that can force a program never
to return -- not exactly a 'main', but halfway there in spirit. If you
use 'STOP RUN' instead of 'GOBACK' or 'EXIT PROGRAM' you convert the
effect of a CALL into an XCTL. The effect isn't noticed when a program
is invoked via EXEC PGM=.
However, 'STOP RUN' has some nasty side effects like killing entire IMS
and CICS regions when executed. And IBM has recommended against its
use at least since LE has come out, it being 99% slower that GOBACK
with RTEREUS. Combine those nasty side effects with its aberrant
behavior of not returning to its caller and it isn't of much use.
But I'm fully off on a tangent now. I'll stop before I digress any
further.
[EMAIL PROTECTED]
The most effective type of birth control is learning Cobol. -DT
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