Natural for OpenVMS Version 6.3.12 for OpenVMS
 —  Statements  —

DEFINE SUBROUTINE

DEFINE [SUBROUTINE] subroutine-name
  statement  

END-SUBROUTINE (structured mode only)

RETURN (reporting mode only)

This document covers the following topics:

For an explanation of the symbols used in the syntax diagram, see Syntax Symbols.

Related Statements: CALL | CALL FILE | CALL LOOP | CALLNAT | ESCAPE | FETCH | PERFORM

Belongs to Function Group: Invoking Programs and Routines


Function

The DEFINE SUBROUTINE statement is used to define a Natural subroutine. A subroutine is invoked with a PERFORM statement.

Inline/External Subroutines

A subroutine may be defined within the object which contains the PERFORM statement that invokes the subroutine (inline subroutine); or it may be defined external to the object that contains the PERFORM statement (external subroutine). An inline subroutine may be defined before or after the first PERFORM statement which references it.

Note:
Although the structuring of a program function into multiple external subroutines is recommended for achieving a clear program structure, please note that a subroutine should always contain a larger function block because the invocation of the external subroutine represents an additional overhead as compared with inline code or subroutines.

Data Available in a Subroutine

Inline Subroutines

No explicit parameters can be passed from the invoking program via the PERFORM statement to an internal subroutine.

An inline subroutine has access to the currently established global data area as well as to the local data area used by the invoking program.

External Subroutines

An external subroutine has access to the currently established global data area. In addition, parameters can be passed directly with the PERFORM statement from the invoking object to the external subroutine; thus, you may reduce the size of the global data area.

An external subroutine has no access to the local data area defined in the calling program; however, an external subroutine may have its own local data area.

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Restrictions

Example 1

The following construction is possible in an object of type subroutine, but not in any other object (where SUBR01 would be considered an inline subroutine):

...
DEFINE SUBROUTINE SUBR01
   ...
   PERFORM SUBR02
   PERFORM SUBR03
   ...
   DEFINE SUBROUTINE SUBR02   
   /* inline subroutine...
   END-SUBROUTINE
 ...
   DEFINE SUBROUTINE SUBR03
   /* inline subroutine...
   END-SUBROUTINE
END-SUBROUTINE
END

Example 2 (invalid):

The following construction is not allowed in an object of type subroutine:

...
DEFINE SUBROUTINE SUBR01   
...
END-SUBROUTINE
DEFINE SUBROUTINE SUBR02
...
END-SUBROUTINE
END

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Syntax Description

Syntax Element Description
subroutine-name
Name of Subroutine:

For a subroutine name (maximum 32 characters), the same naming conventions apply as for user-defined variables; see Naming Conventions for User-Defined Variables in the Using Natural documentation.

The subroutine name is independent of the name of the module in which the subroutine is defined (it may but need not be the same).

statement
Statement(s) to be Executed:
In place of statement, you must supply one or several suitable statements, depending on the situation. For an example of a statement, see Examples below.

END-SUBROUTINE
RETURN

End of DEFINE SUBROUTINE Statement:

In structured mode, the subroutine definition is terminated with END-SUBROUTINE.

In reporting mode, RETURN may be used to terminate a subroutine.

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Examples

Example 1 - Define Subroutine

** Example 'DSREX1S': DEFINE SUBROUTINE (structured mode)               
************************************************************************
DEFINE DATA LOCAL                                                       
1 EMPLOY-VIEW VIEW OF EMPLOYEES                                         
  2 NAME                                                                
  2 ADDRESS-LINE  (A20/2)                                               
  2 PHONE                                                               
*                                                                       
1 #ARRAY    (A75/1:4)                                                   
1 REDEFINE #ARRAY                                                       
  2 #ALINE  (A25/1:4,1:3)                                               
1 #X        (N2) INIT <1>                                               
1 #Y        (N2) INIT <1>                                               
END-DEFINE                                                              
*                                                                       
FORMAT PS=20                                                            
LIMIT 5                                                                 
FIND EMPLOY-VIEW WITH NAME = 'SMITH'                                    
  MOVE NAME            TO #ALINE (#X,#Y)                                
  MOVE ADDRESS-LINE(1) TO #ALINE (#X+1,#Y)
  MOVE ADDRESS-LINE(2) TO #ALINE (#X+2,#Y)
  MOVE PHONE           TO #ALINE (#X+3,#Y)
  IF  #Y = 3                              
    RESET INITIAL #Y                      
    PERFORM PRINT                         
  ELSE                                    
    ADD 1 TO #Y                           
  END-IF                                  
  AT END OF DATA                          
    PERFORM PRINT                         
  END-ENDDATA                             
END-FIND                                  
*                                         
DEFINE SUBROUTINE PRINT                   
  WRITE NOTITLE (AD=OI) #ARRAY(*)         
  RESET #ARRAY(*)                         
  SKIP 1                                  
END-SUBROUTINE                          
*   
END 

Output of Program DSREX1S:

SMITH                    SMITH                    SMITH             
ENGLANDSVEJ 222          3152 SHETLAND ROAD       14100 ESWORTHY RD.
                         MILWAUKEE                MONTERREY         
554349                   877-4563                 994-2260          
                                                                    
SMITH                    SMITH                                      
5 HAWTHORN               13002 NEW ARDEN COUR                       
OAK BROOK                SILVER SPRING                              
150-9351                 639-8963                                  

Equivalent reporting-mode example: DSREX1R.

Example 2 - Sample Structure for External Subroutine Using GDA Fields

** Example 'DSREX2': DEFINE SUBROUTINE (using GDA fields)               
************************************************************************
DEFINE DATA                                                             
GLOBAL                                                                  
  USING DSREX2G                                                         
END-DEFINE                                                              
*                                                                       
INPUT 'Enter value in GDA field' GDA-FIELD1                             
*                                                                       
*  Call external subroutine in DSREX2S                                  
*                                                                       
PERFORM DSREX2-SUB                                                      
*                                                                       
END                                                                    

Global Data Area DSREX2G Used by Program DSREX2:

1 GDA-FIELD1                       A    2                            

Subroutine DSREX2S Called by Program DSREX2:

** Example 'DSREX2S': SUBROUTINE (external subroutine using global data)
************************************************************************
DEFINE DATA                                                             
GLOBAL                                                                  
  USING DSREX2G                                                         
END-DEFINE                                                              
*                                                                       
DEFINE SUBROUTINE DSREX2-SUB                                            
*                                                                       
  WRITE 'IN SUBROUTINE' *PROGRAM '=' GDA-FIELD1                         
*                                                                       
END-SUBROUTINE                                                          
*                                                                       
END                                                                    

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