re: what is unclear about 01 02 03 -Reply

>>>> Wynn Osborne <wynn@praxis.net> 04/30/98 01:27am >>>
><snip>
>>>      C   01 02 03                EXSR SR001
>>>
>>>Can left side indicators be all wrong?  I know, I know.  I won't use
>>> them, but really, what is unclear about that line of code?
><snip>
>>Exactly what is an 01, 02, & 03?


Wynn, please forgive me if my flippant answer caught your serious search
for knowledge.  I "assumed" that your request was a humorous one.

As Scott has mentioned, they are Indicators; Binary Switches that can be
set/unset to indicate various conditions in your program.

In early incarnations of RPG and RPG-II, you had to use the left hand
columns of the RPG calculation specs.  Then, in RPG-III, a system array,
*IN, was created which allowed such interesting constructs as:

                        MOVE '110'    *IN,01

This line would move values of 1, 1, and 0 to indicators 01, 02, and 03
(elements 1, 2, and 3 of the array).

In addition to array *IN, you can also refer to the indicators as *IN01,
*IN02, and *IN03...

The biggest problem of using the left-hand indicators was that you had to
code them on every line you wanted to be conditioned by those indicators.
Early compilers would 'optimize' your object code if the indicators
'matched' from line to line.  The current compilers do not do this; they
assume that indicator-controlled logic is passe'.

==Paul E Musselman,
       G.O.V.
(Grizzled Old Veteran)
PaulMmn@ix.netcom.com





>
>                    --------------------------------
>
>Don't let the "geezers" on the list scare you, Wynne - they're usually
>harmless, even while resurrecting all kinds of obscure RPG
>programming constructs with out actually answering the original
>question :)
>
>01, 02, and 03 in the code snippet are references to indicators.
>The RPG language allows for 99 of 'em (ignoring all the obscure and
>pre-historic Lx's, Mx's, Cx's, etc.) and they're basically a pre-defined
>variable of an "on/off, true/false, yes/no" type - "1" = Yes, True, On
>& "0" = No, False, Off.  When 01 is placed in columns 9-10, 12-13,
>or 14-15 (not being a geezer, I probably have the actual columns
>wrong :)) of RPG III source code, it says "Only execute this line of
>code if indicator 01 is "ON", e.g. has a value of "1".  So the line of
>code listed above only executes if indicators 01, 02, and 03 all have
>a value of "1"
>
>RPG has been slowly moving away from it's dependance on cryptic
>indicators (RPV IV only allows 2 left hand column indicators and
>provides keyword type replacements for most of those referred to
>and not so fondly remembered by the older folks.)  This is, IMHO, all
>to the good.  If you don't know what they are, don't start using 'em.
>That'll spare you having all the hair-color changing horror stories
>that some of the grizzled veterans on this list enjoy swapping from
>time to time ;)
>
>Scott Cornell
>Mercy Information Systems
>
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