RE: Problem Found! Need solution

["Hopkins, Bill" <BHopkins@xxxxxxxxxxxxx>]

Thanks Joe

It's the fact that 4B is NOT equivalent to BINARY(4) that catches most folks
when they're first doing this.  Maybe Jon can shed a little light on that
particular mystery.

I understand now.
Question Mike's code message also define last parm D SplfNumber as 8B 0 in
DataQueue DS. Should not that be a from 1 and to 4 or 9B or 10I since parm
is "8 Spooled file number Input Binary(4)".

Thanks
Bill Hopkins

-----Original Message-----
From: Joe Pluta [mailto:joepluta@PlutaBrothers.com]
Sent: Tuesday, September 17, 2002 9:15 AM
To: rpg400-l@midrange.com
Subject: RE: Problem Found! Need solution


> From: Hopkins, Bill
>
> Understand code var. length " Inz(%Len(Receiver)) " which allows you to
> change length of receiver(good idea). But I not seeing length of receiver
> var. field size 10I?
>
> "Length of receiver variable
> INPUT; BINARY(4)
> The length of the receiver variable. If the length is larger than the size
> of the receiver variable, the results are not predictable. The minimum
> length is 8 bytes."

This has caught me several times.  BINARY(4) means a 4-byte binary field.
Now, a little mathematics shows that a 4-byte binary field is 32 bits long,
and so can hold a number up to 2^32, or 4,294,967,296.  In order to define a
decimal number large enough to hold the largest 4-byte binary number, you
must specify 10 digits.  Thus, to define a decimal integer that is
equivalent to a 4-byte binary number, you specify 10I.  In fact, I use this
little table:

3I = 1 byte
5I = 2 bytes
10I = 4 bytes
20I = 8 bytes

It gets even more confusing when you use RPG fields of type "B" rather than
"I".  For some reason that I'm not privy to, a 9B field is "equivalent" to a
10I (which is a 4-byte binary field), while a 4B is equivalent to a 5I,
which is a two-byte field.  It's the fact that 4B is NOT equivalent to
BINARY(4) that catches most folks when they're first doing this.  Maybe Jon
can shed a little light on that particular mystery.

In any event, because of the varying field types and their non-intuitive
relationship to one another, it's quite easy to make a mistake.

Finally, there's one more gotcha.  Let's take a data structure field, where
you can optional specify the from and to positions, or just the length.  If
you specify just a length of 4 for a field of type B, it will define a field
of type 4B, which as we've seen is only two bytes long.  However, if you
specify a from and to position that defines the field to be four bytes long
(for example, from position 1, to position 4), the compiler will create a
field of 9B, which is four bytes long.

Confused yet?

So, when defining a field equivalent to BINARY(4), you have the following
options:

1. Define a field of 10I, 10U or 9B
2. Define a subfield four positions long of any of those types (I/U/B)

Since 99% of my uses of binary/integer fields are currently in data
structures, I tend to always define from and to positions.  It saves me
grief.

Joe

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