Re: Question about legacy coding style

[Booth Martin <booth@xxxxxxxxxxxx>]

At one time there was no such op-code as Z-ADD.  Also, factor 1 always 
had to be filled in.

So the only way to clear FIELDB was with a blank-after in the O specs or 
something like this:
 C   FIELDB    MOVE  *ALL'0'   FIELDB
or
 C   FIELDB    SUB   FIELDB    FIELDB
or
 C   FIELDB    MULT  0         FIELDB

 C   FIELDA    ADD  FIELDB     FIELDB

The Z-ADD op code was a breakthrough.   :)

Z-ADD is "zero then add" or "zero the result field and then add factor 1 
and factor 2".






On 3/24/2011 5:10 AM, Craig Pelkie wrote:
> Another question about "why" (not "what is it doing").
>
> Why use a MOVE opcode when initializing a numeric field as opposed to the
> more clearly numeric-only Z-ADD opcode?
>
> The question is motivated towards understanding what the historical bias
> was, in terms of choosing MOVE instead of Z-ADD.
>
> Craig Pelkie
>
>
> -----Original Message-----
> From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
> On Behalf Of Jim Franz
> Sent: Wednesday, March 23, 2011 8:43 PM
> To: RPG programming on the IBM i / System i
> Subject: Re: Question about legacy coding style
>
> in S36 code that would be
>   C  U1NU1     MOVE     X2DAT     X2DAT     6 0
>
> and your probably correct - to define a field&  someone felt it must never
> be executed...
>
> In the 80's i did one of these in a subroutine executed 1st time into
> calcs..
>
> C                    MOVE    *ZEROS     X2DAT     6 0
> or
> C                     Z-ADD  0                  X2DAT     6 0
>
> Jim Franz
> ----- Original Message -----
> From: "Craig Pelkie"<craig@xxxxxxxxxx>
> To:<rpg400-l@xxxxxxxxxxxx>
> Sent: Wednesday, March 23, 2011 11:20 PM
> Subject: Question about legacy coding style
>
>
> > This is in some old code we are looking at:
> >
> > C U1
> > CANNU1 MOVE X2DAT X2DAT 6 0
> >
> > C U1
> > CANNU1 MOVE X2UDAT X2UDAT 6 0
> >
> > C U1
> > CANNU1 MOVE X2TDT2 X2TDT2 6 0
> >
> > C U1
> > CANNU1 MOVE X2DDAT X2DDAT 6 0
> >
> >
> > It looks like an obscure way to define a field.
> >
> > What was the reasoning behind defining it like this?
> >
> > Thanks,
> > Craig Pelkie
> >
> >
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