The Retrieve Century command provides a solution for a sliding date
window. The intent is that you would input a 2 digit year (such as
96 or 02) and be returned both a 2 digit century (such as 19 or 20)
and a one digit century (such as 0 or 1). The sliding window is
based on 50 years in either direction from the current year. The
function may used as a command, a sub program, or a subroutine in
your program.
A typical series of commands would be:
DCL &YY *CHAR LEN(2)
DCL &CEN2 *CHAR LEN(2)
DCL &CEN1 *CHAR LEN(1)
.
. /* Your code to prime &YY */
.
RTVCEN INPUTYEAR(&YY) RTNCEN2(&CEN2) RTNCEN1(&CEN1)
Your program then uses either or both &CEN2 or &CEN1 to assume a
century.
Some business data such as those dealing with birthdays or property
records will exceed a 100 year span and can only be handled by
providing for 4 digit dates throughout an application.
Most business data does not last more than 50 years. Consequently,
it is possible to assume a century for many applications by using a 2
digit year (such as 98 or 02) to determine a 2 byte century value
(such as 19 or 20) or a 1 byte century value (such as 0 or 1).
A sliding window differs from a fixed window. A typical fixed window
solution would assume:
Years 40 - 99 = 20th century
Years 00 - 39 = 21st century
The advantage of the sliding window approach allows the program to be
used for hundreds or thousands of years without change. A typical
fixed window approach requires a change in about 40 years.
The Retrieve Century function determines the current year and then
assumes a century based on 50 years in either direction of the
current year.
For example, based on the following current years, the subroutine
would assume a century:
Current year Input year assumptions
------------ -----------------------------
1994 45 - 99 = 19 00 - 44 = 20
1998 49 - 99 = 19 00 - 48 = 20
2000 51 - 99 = 19 00 - 50 = 20
2030 81 - 99 = 19 00 - 80 = 20
2060 11 - 99 = 20 00 - 10 = 21
Different interfaces
--------------------
The following interfaces are supported:
** The command RTVCEN which may only be used in a CL program.
The command interface is adequate if you are not going to
iterate on the command (such as use it for every data base
record read).
** A sub program TAARPHDR which is the processing piece of
RTVCEN.
** As a subroutine in your RPG program.
** As a subroutine in your RPGLE program.
A test program to allow you to try different assumed years.
Performance
-----------
The command interface is not efficient, but is adequate if you need
the function only once or a few times.
Better performance can be gained by calling the sub program
(TAARPHDR3) or by using a subroutine in your RPG program.
If you are calling the sub program on an iterative basis, be sure to
set the SETLR parameter to *NO to avoid reactivating the sub program.
Using a sub program approach
----------------------------
You would call the program with a parameter list such as the
following RPG code:
C CALL 'TAARPHDR' Rtn century
C PARM YY 2 Input year
C PARM CEN2 2 Rtn cen 2
C PARM CEN1 1 Rtn cen 1
C PARM '*YES' SETLR 4 Set LR
All parameters must be passed. The SETLR value must contain either
*YES or *NO. *YES causes the called program to end with LR on
meaning the program is deactivated. *NO should be used when you
intend to iteratively call the program and want to keep the program
activated.
Using the subroutine in an RPG program
--------------------------------------
The source member TAARPHDR3 has both the standard subroutine and
instructions for its use.
First use the CPYTAA tool to copy the code from the TAA Archive to a
normal source member:
CPYTAA TAAARCMBR(TAARPHDR3)
This will copy the code to the TAARPHDR3 member in the QATTRPG file
in TAATOOL.
You may then use the normal SEU Browse/Copy option (F15) to copy the
code to your own program and follow the instructions.
For example, the following inputs a 2 digit date to the standard
field ZYYY, calls the subroutine, and uses the return field of ZYCEN2
for the 2 digit century value.
C MOVE yy ZYYY Inp to subr
C EXSR ZYCVT Date slide
C MOVE ZYCEN2 cc 2 Return 2
Using the subroutine in an RPGLE program
----------------------------------------
The source member TAARPHDR4 has both the standard subroutine and
instructions for its use.
First use the CPYTAA tool to copy the code from the TAA Archive to a
normal source member:
CPYTAA TAAARCMBR(TAARPHDR4)
This will copy the code to the TAARPHDR4 member in the QATTRPG file
in TAATOOL.
You may then use the normal SEU Browse/Copy option (F15) to copy the
code to your own program and follow the instructions.
For example, the following inputs a 2 digit date to the standard
field ZYYY, calls the subroutine, and uses the return field of ZYCEN2
for the 2 digit century value.
C MOVE XXXXX ZYYY
C EXSR ZYCVT
C MOVE ZYCEN2 cc 2
Invalid year data
-----------------
The two byte field passed to the subroutine must contain valid digits
00 - 99. If not, asterisks (*) are placed in the return values.
Technique used
--------------
The RPG *DATE function is used to determine the current 4 century
year. 49 years are subtracted to find the minimum year range and 50
years are added to find the maximum year range.
The RTNCEN2 value is valid for current years of 0049-9949.
The RTNCEN1 value is valid for current years of 1949-2849.
Test program
------------
A test program exists to allow you to try out the subroutine with
different values assumed as the current year.
To test the program, pass a parameter for the assumed current year
such as:
CALL TAARPHDR2 PARM('1999')
Spooled output occurs to the QPRINT spooled file with the results for
various 2 digit years.
Command parameters *CMD
------------------
INPUTYEAR The two digit year to assume a century for. For
example, you would input a YY value such as 98 or
02.
The parameter must contain numeric data in a range
of 00 - 99. If not, asterisks will be placed in the
two return parameters.
RTNCEN2 The two digit assumed century that is returned. For
example, 19 or 20. The parameter must be specified
as *CHAR LEN(2).
RTNCEN1 The one digit assumed century that is returned. For
example, 0 for the 20th century and 1 for the 21st
century. The parameter must be specified as *CHAR
LEN(1).
SETLR A *YES/*NO value for how to end the RPG program
which is the processing function of RTVCEN. *YES
causes the RPG program to end with LR on meaning the
program is deactivated.
*NO should be used when you intend to iteratively
use the command and want to keep the RPG program
activated.
Restrictions
------------
Because the RTVCEN command returns variables, the command may only be
used in a CL program.
The RTNCEN2 value is valid for current years of 0049-9949.
The RTNCEN1 value is valid for current years of 1949-2849.
When the subroutine is used for the first time after the program is
initialized, several values are set. If the program is in operation
past midnight on Dec 31 of the last day of a century, the window
remains fixed and would only be valid for 49 years into the future.
Prerequisites
-------------
None.
Implementation
--------------
You must copy the code into your program and follow the instructions.
Objects used by the tool
------------------------
Object Type Attribute Src member Src file
------ ---- --------- ---------- ----------
RTVCEN *CMD TAARPHD QATTCMD
TAARPHD *CLP CLP TAARPHDC QATTCL
TAARPHDR *PGM RPG TAARPHDR QATTRPG
TAARPHDR2 *PGM RPG TAARPHDR2 QATTRPG
TAARPHDR3 QATTRPG
TAARPHDR4 QATTRPG
The TAARPHDR source is the processing function for RTVCEN.
The TAARPHDR2 source is the test program.
The TAARPHDR3 source is the RPG subroutine to be copied to your
program.
The TAARPHDR4 source is the RPGLE subroutine to be copied to your
program.
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