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by M Gopalakrishnan
Commercial System Division
Overview
This version of MPE/iX provides enhancements to the operating system for the
year 2000 and beyond. The enhancements include the enhancements to the
operating system commands, utilities, VPLUS and databases. This article
explains the enhancements.
Background
The year 2000 issues stem from the ability to handle correctly the year 2000
and beyond. This is particularly an issue for systems and applications that
are using a two-digit year to express dates. There are a few commands,
utilities, and databases in MPE/iX which were designed to handle two-digit
years and these had to be enhanced to support year 2000 and beyond.
The year 2000 is a leap year, and this also had to be addressed. The MPE/iX
operating system uses the Gregorian calendar and its definition of leap year:
any year that is exactly divisible by 400, or that is exactly divisible by 4
and not exactly divisible by 100.
Two-Digit Years Interpretation
One of the ways for handling two-digit year input is to interpret the years in
the method called fixed window method. In this method, the two-digit years map
as follows:
- 00 .. 49 maps to 2000 .. 2049
- 50 .. 99 maps to 1950 .. 1999
For example, both of the following STREAM commands will schedule the
JOBFILE as January 21, 2001:
:STREAM JOBFILE;DATE=01/21/2001
:STREAM JOBFILE;DATE=01/21/01
Intrinsics
The CALENDAR intrinsic and CALENDAR date representation
format are widely used in MPE/iX. There are many other intrinsics that accept
or return dates in calendar format. The following discussion clarifies the
interpretation of calendar format year value.
CALENDAR Intrinsic
The CALENDAR intrinsic returns the CALENDAR date, including
the day of year and the year of century. The existing CALENDAR
intrinsic documentation refers to the year as "year of century." This should
be interpreted as "year since 1900."
The new definition of the CALENDAR intrinsic is as follows:
Syntax
U16
date := CALENDAR;
where date is a 16-bit unsigned integer (assigned functional
return).
This returns the CALENDAR date in the following format:
Table 9-1 CALENDAR Date Formats
| Bits |
Value/Meaning |
| 7:9 | day of year |
| 0:7 | year since 1900 |
Description
For the year 2000, the CALENDAR intrinsic will return the year as 100,
for 2001 as 101, and so on. With this current interpretation,
CALENDAR format can handle years through 2027.
All intrinsics accepting or returning dates in CALENDAR format will
behave the same way as the CALENDAR intrinsic.
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NOTE: If your application uses the CALENDAR intrinsic or
CALENDAR format, it may be required to verify the source for
conformance to the above interpretation.
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HPFOPEN/FOPEN Intrinsic
HPFOPEN item 31 (labeled tape expiration parameter) and
FOPEN (formmsg label tape parameter) will accept both
two- and four-digit years as the labeled tape expiration date. This is the
same as the FILE command expiration date parameter. For an
interpretation of two-digit years, refer to the section, "Two-Digit Years
Interpretation," in this article.
New Date Intrinsics
This version of MPE/iX has new intrinsics added to manipulate dates in various
formats. For more information, refer to the article, "New Date Intrinsics for
MPE/iX," in this Communicator.
Commands
The following commands are enhanced to support both two- and four-digit years.
For an interpretation of two-digit years, refer to the section, "Two-Digit
Years Interpretation." New syntax for the commands with parameters accepting
years follows:
- STREAM command
:STREAM jobname;DATE=datespec
where datespec is the date for streaming the job in the
format mm/dd/[yy]yy. If omitted, the current date is
used.
- FILE Command
:FILE [;LABEL=[ [volid][,[IBM][,[expdate][,seq] ] ] ] ]
[ [ [ [ANS] ] ] ]
where expdate is the expiration date in the format
mm/dd/[yy]yy.
- SETCLOCK command
:SETCLOCK ;DATE=datespec
where datespec is the local date in the form
mm/dd/[yy]yy.
- LISTSPF/SPOOLF command
:LISTSPF/SPOOLF ;SELEQ=[DATE=mm/dd/[yy]yy]
- STORE Command
:STORE [{;DATE<=accdate}]
[{;DATE>=moddate}]
where accdate and moddate are the accessed and modified
dates in the form mm/dd/[yy]yy.
CI Variables
The available HPYEAR variable is corrected to return the last two
digits of the current system year, and a new CI variable is added to have the
four-digit current system year.
Existing variable:
Title not available (CI Variables )
- HPYEAR
- is a global variable used by the CI that shows the last two digits of
the current year; the initial value is the year at logon. Type= R I
For example, HPYEAR will have 0 for year 2000 and 5 for year
2005.
New four-digit year variable:
Title not available (CI Variables )
- HPYYYY
- is a global variable used by the CI that shows the current year; the
initial value is the year at logon. Type= R I
For example, for year 2000, HPYYYY will have 2000.
- HPSPLITYEAR
- is a global variable used by the CI that shows the current century split
year; the initial value is 50. Type=W I
This variable is used in the new date intrinsics to manipulate dates in
various formats.
Utilities
CLKUTIL and START utilities/commands available in ISL
(Initial System Loader) are enhanced to accept dates both in two- and
four-digit years.
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