Re: RPG IV Pointers

["Joep Beckeringh" <joep@xxxxxxxxxxxxxxxxxxx>]

Jim,

Your first example:
> D MyPointer                         S                              *
This tells the compiler to define a variable called MyPointer of type
pointer.  In other words: storage is allocated, which you can refer to by
its name MyPointer.  The RPG compiler is a friendly one and even initializes
your variable.  So its initial value is *NULL, in other words it doesn't
point anywhere (yet).
> D MyField                            S                        50
50 bytes of storage are allocated for your variable MyField.
> C                                              Eval     MyPointer =
%Addr(MyField)
The address of the (first of the) 50 bytes you know by the name of MyField
is assigned to MyPointer.  Only after an assignment like this is your
pointer useable.

Your second example:
> D MyPointer                         S                              *
Same as above.
> D MyField                            S                        50
Based(MyPointer)
No storage is allocated.  You only instruct the compiler to make the 50
bytes of storage that MyPointer is going to point to addressable as MyField.
You have to assign a pointer value to MyPointer before you can do anything
with MyField.


Joep Beckeringh


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