The Linkage Section is how modules pass data from the top module in the chain down, and then back. In fact, they don't "pass" the data at all, but use a single address that is established by the top-most caller. All modules use the same address which is located in the top-most module's DSECT, irrespective of the variable's name...although in your case the name is the same in both caller and called module. This is how external CALLs work.
As you note, INTERNAL calls establish a new variable unless the GLOBAL attribute is applied. Why the compiler was built that way is an interesting question perhaps Tom Ross can answer. Remember, internal subroutines are relatively new in COBOL, but even so, you are asking the question some 20 years too late. BY CONTENT may be what you want in the CALL statement. You can override the standard behaviour ( BY REFERENCE) by using BY CONTENT, where the called module can change the value locally, but not affect the caller; or by using BY VALUE (not recommended by me) where the value is passed and the called module can change the format as long as it's commensurate, e.g. Binary to Fixed Decimal or Float (comp-2). You can mix CONTENT, REFERENCE and VALUE in the same call for different variables. BY REFERENCE (the default) Prog_A: 1 A PIC X(4) value 'abcd'.. 1 B PIC S9(9) Binary value 3000. Procedure Division. Call Prog_B using A, B display B *> = 1066 display A *> = "ty" Prog_B: Linkage Section: 1 X PIC X(4). 1 N PIC S(9) Binary, Procedure Division. Display X *> = 'abcd' Display N *> = 3000 compute N = 1066 move 'ty' to X goback. BY CONTENT Prog_A: 1 A PIC X(4) value 'abcd'.. 1 B PIC S9(9) Binary value 3000. Procedure Division. Call Prog_B using BY REFERENCE A, BY CONTENT B display B *> = 3000 *> Not changed by the subroutine display A *> 'ty' *> Changed by the subroutine Prog_B: Linkage Section: 1 X PIC X(4). 1 N PIC S(9) Binary, Procedure Division. Display X *> = 'abcd' Display N *> = 3000 compute N = 1066 move 'ty' to A goback. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
