Re: [Tiny-cobol-users] Preprocessor

[Fred M. <fr...@mo...>]

On Wednesday 14 January 2009 12:57, David Essex wrote:
> deu439 wrote:
> > Thanks, but I _didnt_ mean structures.
> >
> > Typedef; can be used for define new data type/structures.
> > So I can declare new variable/struct with defined aligment.
> >
> > Like this:
> >
> > //define data type "NAME"
> > typedef struct{
> > int a;
> > int b;
> > }NAME;
> >
> > main(){
> > //declare struct
> > //with "NAME" aligment
> > NAME declared_struct;
> > }
> >
> > Sorry whether it's too intuitive.
>
> AFAIK, COBOL (85 standard) does not differentiate between a
> declaration and definition (memory allocation). Meaning it does both
> in one step.

I don't understand the original question of OP, but I would like to add 
to your statement above.

In a WORKING-STORAGE SECTION, declarations allocate memory and declare a 
memory layout.

In a LINKAGE SECTION, declarations don't allocate memory but just 
declare a memory layout. The memory is in general allocated in the 
calling program in the WORKING-STORAGE SECTION.

Example :

  PROGRAM-ID. A.                   <--- Main program.
  ...
  WORKING-STORAGE SECTION.         <--- allocation and layout.
  01  AREA-A-1.
    03 FIELD-A-1-A PICTURE X(7).
    03 FIELD-A-1-B PICTURE X(3).
  01  AREA-A-2.
    03 FIELD-A-2-A PICTURE X(7).
    03 FIELD-A-2-B PICTURE X(3).
  01  AREA-A-3.
    03 FIELD-A-3-A PICTURE X(7).
    03 FIELD-A-3-B PICTURE X(3).
  PROCEDURE DIVISION.
  START SECTION.
  P00.
      CALL "B"
          USING AREA-A-1
                AREA-A-3.
  EOS.
      STOP RUN.

  PROGRAM-ID. B.                   <--- Subroutine.
  ...
  LINKAGE SECTION.                 <--- Only layout per 01 level.
  01  AREA-B-1.
    03 FIELD-B-1-A PICTURE X(7).
    03 FIELD-B-1-B PICTURE X(3).
  01  AREA-B-2.
    03 FIELD-B-2-A PICTURE X(7).
    03 FIELD-B-2-B PICTURE X(3).
  PROCEDURE DIVISION USING AREA-B-1
                           AREA-B-2.
  START SECTION.
  P00.
      ....
  EOS.
      EXIT PROGRAM.

PLease notice that the subroutine B does not know if the arguments 
AREA-B-1 and AREA-B-2 are located in adjacent area's or not. The main 
program A knows they're NOT.

Often such structures are put in copy members in order to avoid 
differences in declarations. But that results in another problem : 
VALUE clauses are (were ?) not allowed in the linkage section.
-- 
Fred Mobach - fr...@mo... - pos...@mo...
website : http://fred.mobach.nl
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