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Y2K Issue: Coping with the
dreaded gregorian-to-julian subprograms
by David Shelby Kirk
If you've been on a Y2K project, you've probably already encountered
one of those dreaded subprograms that convert gregorian-to-julian or
julian-to-gregorian.
Often, they totally ignore the century issue and making them work correctly
can be challenging. Well, there's an easier way to solve this problem
than in modifying that old code. Just use the intrinsic functions in
COBOL
for MVS (or OS/390.)
Earlier intrinsic functions:
For background information, when IBM first introduced this new family
of COBOL, the language name was COBOL/370 (now changed with the later
version to COBOL for MVS.) In that first edition, IBM introduced intrinsic
functions, four of which are of special interest in a Y2K project. At
the time, there was little thought of them. They are INTEGER-OF-DAY, INTEGER-OF-DATE,
DAY-OF-INTEGER and DATE-OF-INTEGER. These four functions convert a julian
or gregorian date into a non-date integer, allowing easy conversions between
the two formats.
For example:
compute field-i = function integer-of-day (julian-data-field)
compute field-g = function date-of-integer (field-i)
converts a julian date element into an integer, stores it in field-i and
the next statement converts the integer into a gregorian date element, being
stored in field-g.
Newer Y2K intrinsic functions:
Early in 1998 IBM introduced some Y2K intrinsic functions to COBOL for MVS.
These new functions provided windowing capabilities to ease the conversion
of julian and gregorian dates with 2-digit years into 4-digit years. A discussion
of those functions would be a separate article.
Mixing both sets of intrinsic
functions:
Now, in drawing the functions together is where the true power of these
intrinsic functions shine. The new functions are able to convert a date
element with a 2-digit year into one with a 4-digit year. If we combine
that power with the earlier functions' ability to convert from one format
to another, we can eliminate the need for a conversion subprogram - and
the need to remedial any existing ones. Also, the variable for a function
can be the output of another function. So, we can nest them together. Let's
do it in this example:
Original code, prior to conversion:
call 'gregjul' using date-field-j, date-field-g
where the routine is to convert a date element from date-field-j into date-field-g).
Instead of converting the 'gregjul' subprogram to be Y2K-compliant, we can
eliminate it and use one compute statement that nests 3 intrinsic functions:
one to create a Y2K date, one to convert the date element to an integer,
and one to convert the integer to the desired date format.
Here is that example:
compute date-field-g = function date-of-integer
(function integer-of-day
(function day-to-yyyyddd (date-field-a)))
Note: To keep the article abbreviated, I did not show the PIC clauses for
the data elements. Those should be whatever length the application requires.
For example, many windowed applications retained their 2-digit year data
fields, using the windowing technique for logic control. That approach would
work here as well.
About the Author:
David Shelby Kirk, an outstanding expert in the field, is an instructor,
author, and a successful consultant with MVS Training, Inc. His newest book
COBOL for OS/390 Power Programming with Complete Year 2000 Section is now
available to own. Call (800) 356-9093 or contact dkirk@mvs-training.com
to order.
MVS Training, Inc. helps clients optimize their people's programming and
systems administration skills by providing state-of-the art mainframe training
tailored to the client's work environment and their information technology
personnel's needs. Specialists in COBOL, NEW OFFERINGS include public workshops,
and book publications. For more information contact: (800) 356-9093, sales@mvs-training.com
or www.mvs-training.com.
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