procedure division header where define the varible

Hello,

This is a Rocket COBOL extension.

When you pass a parameter to a subprogram and the subprogram’s procedure division using statement specifies the parameter in the working-storage or file-section then it is  as if the parameter were actually passed in the linkage section and then its contents are moved to the data item in working-storage or the file section. If you modify this item in the subprogram, it will not affect the parameter in the main program. This is documented under General rules for format 1 of the procedure division header USING statement, general rules 4 which states:

 If data-name-1 is defined as a level 01 or a level 77 entry in the File Section or Working-Storage Section then the activated runtime element operates as if a data item had been declared in the Linkage Section with the same data declaration as data-name-1 and the contents of that data item were moved to data-name-1 prior to executing the first statement in the activated runtime element. In an initial program, these values are overwritten by the initialization of the program's working storage data and are therefore not available to the called program.

It is possible to share a data-item between a main program and a subprogram without passing it on the CALL statement by specifying the data item as being EXTERNAL in both programs.

01 my-param  pic x(5) external.

When you share data like this it means that the data item does not belong to any one program but can be shared between all programs in the run-unit defining it this way.

Good morning Chris, I'm very interested in this option, but I've never used it before. Could you show me an example or give me a link to the documentation?

Good morning!

I am assuming that you are referring to using EXTERNAL data items.

The following simple example will demonstrate its use.

identification division.
program-id. mainprog.
data division.
working-storage section.
01 my-external-data   is external.
   05 my-field-1   pic x(20).
   05 my-field-2   pic 9(5).
procedure division.

    move "my shared data" to my-field-1
    move 12345 to my-field-2
    call "subprog"
    display "back from subprog"
    display my-field-1
    display my-field-2

    goback.

 identification division.
 program-id. subprog.
 data division.
 working-storage section.
 01 my-external-data   is external.
    05 my-field-1   pic x(20).
    05 my-field-2   pic 9(5).
 procedure division.

     display "in subprog"
     display my-field-1
     display my-field-2
     move "set in subprog" to my-field-1
     move 98765 to my-field-2
     goback.

 end program subprog.

Is there a limit to the size of variables defined as EXTERNAL?

According to the docs page covering size limits it says it is “not specifiable”.

I believe this means that it has the same limits as a non-external data item.

Size and Number of Data Items