RE: How do I retrieve the RRN of a PF or LF in a RPG program.

The example I gave using the B data type was a working example from S/38 RPG III. (late 80s/early 90s)

Paul

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From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Jon Paris
Sent: Tuesday, August 25, 2020 6:42 PM
To: RPG programming on IBM i <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: How do I retrieve the RRN of a PF or LF in a RPG program.

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The basic notion behind the B data type was to allow the definition of binary variables in RPG (and COBOL works the same way incidentally) in the traditional way i.e. in terms of number of digits or characters,

Numbers in packed or zoned were capable of holding the full range of values i.e. a 5 digit number could hold -99,999 to +99,999 so when the B type was introduced it was decided to constrain its capacity to the maximum number of digits whose full range could be expressed within it. A 4 byte binary can represent values with 10 digits, but RPG and COBOL constrained it to 9 digits because that was the highest number where the full capacity of that many digits could be expressed.

In order to maintain this limit, when a numeric operation is performed on a type B field the value is copied to a packed field of equivalent precision, the operation is performed (with potential overflow) and the resulting packed value copied back to the B type variable. The result is that a B data type - which should theoretically be the most efficient was to represent (say) loop counters, offsets etc, was actually the least efficient.

The decision was made back in the (I think) RPG III days on S/38. Personally I think it was silly - but then I think Int(10) instead of Int(4) was a mistake too - but the decision was made for similar reasons - i.e. defining numerics in terms of digits not storage occupancy.

When we developed RPG IV the decision was taken to add the U and I data types to allow for real integers. The old B type had to stay for compatibility but is strongly discouraged. Except that sadly a great many IBM examples were never updated (and have not been to this day) to get rid of the stupid B data types,

On Aug 25, 2020, at 5:33 PM, James H. H. Lampert <jamesl@xxxxxxxxxxxxxxxxx> wrote:

On 8/25/20 2:24 PM, Bruce Vining wrote:

Oh please, don't use the B data type, you (unless something in RPG
has
changed) just made a mess of the RRN. Int is how IBM defines it and
is how the program should treat it.

Quite. As I recall, a "B" is only binary in a record within a file. Shocked my <E. asinius> across the room, the first time I got bit by that little "gotcha." What WERE they THINKING?

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JHHL
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