An RPG IV subroutine can be processed from any point in the calculation operations. All RPG IV operations can be processed within a subroutine, and these operations can be conditioned by any valid indicators in positions 9 through 11. SR or blanks can appear in positions 7 and 8. Control level indicators (L1 through L9) cannot be used in these positions. However, AND/OR lines within the subroutine can be indicated in positions 7 and 8.
Fields used in a subroutine can be defined either in the subroutine or in the rest of the procedure. In either instance, the fields can be used by both the body of the procedure and the subroutine.
A subroutine cannot contain another subroutine. One subroutine can call another subroutine; that is, a subroutine can contain an EXSR or CASxx. However, an EXSR or CASxx specification within a subroutine cannot directly call itself. Indirect calls to itself through another subroutine should not be performed, because unpredictable results will occur. Use the GOTO and TAG operation codes if you want to branch to another point within the same subroutine.
Subroutines do not have to be specified in the order they are used. Each subroutine must have a unique symbolic name and must contain a BEGSR and an ENDSR statement.
The use of the GOTO (branching) operation is allowed within a subroutine. GOTO can specify the label on the ENDSR operation associated with that subroutine; it cannot specify the name of a BEGSR operation. A GOTO cannot be issued to a TAG or ENDSR within a subroutine unless the GOTO is in the same subroutine as the TAG or ENDSR. You can use the LEAVESR operation to exit a subroutine from any point within the subroutine. Control passes to the ENDSR operation for the subroutine. Use LEAVESR only from within a subroutine.
A GOTO within a subroutine in the cycle-main procedure can be issued to a TAG within the same subroutine, detail calculations or total calculations. A GOTO within a subroutine in a subprocedure can be issued to a TAG within the same subroutine, or within the body of the subprocedure.
See Figure 183 for an example of coding a subroutine.