CALL USING Parameters

Parameters can pass in three ways from MAINPROG to SUBPROG, and those are -

USING BY REFERENCE
USING BY CONTENT
USING BY VALUE

USING BY REFERENCE phrase -

BY REFERENCE passes the address of the parameter memory location to the SUBPROG. The SUBPROG receives the pointer to the parameter memory location when we pass the parameters using BY REFERENCE. If the SUBPROG modifies the value of the passing parameter, the new value will be reflected in the MAINPROG.

It is the default option if BY phrase is not coded with a CALL statement.

Syntax -

CALL subprog-name USING BY REFERENCE PARM1, PARM2, ...

Example -

CALL WS-SUBPROG USING BY REFERENCE WS-INP1, WS-PARM2, ...

BY CONTENT phrase -

BY CONTENT phrase is used to pass the copy of the data to the SUBPROG. The SUBPROG receives a copy of the variable's data at the time of the execution when we pass the parameters using the BY CONTENT. If the SUBPROG modifies the value of the passing input variable, the new value will not reflect in the MAINPROG.

Syntax -

CALL subprog-name USING BY CONTENT PARM1, PARM2, ...

Example -

CALL WS-SUBPROG USING BY CONTENT WS-PARM1, WS-PARM2, ...

BY VALUE phrase -

BY VALUE phrase is similar to the BY CONTENT and is used to pass the copy of the data to the SUBPROG. The SUBPROG receives a copy of the variable's value at the time of the execution when we pass a variable using the BY VALUE. BY VALUE clause is primarily introduced for communicating with non-COBOL programs. It can also be used for COBOL-to-COBOL communication.

Syntax -

CALL subprog-name USING BY VALUE PARM1, PARM2, ...

Example -

CALL WS-SUBPROG USING BY VALUE WS-INP1, WS-INP2, WS-RESULT.

Note! Passing parameters (BY REFERENCE, BY CONTENT, BY VALUE) should only code with CALL..USAGE, but not with PROCEDURE DIVISION USAGE.

Practical Example -

Scenario - CALL BY REFERENCE from MAINPROG to SUBPROG and receiving the result back from SUBPROG.

MAINPROG -

Full Example

       ...
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-VAR.
          05 WS-INP1      PIC 9(02) VALUE 47. *> Input1
          05 WS-INP2      PIC 9(02) VALUE 25. *> Input2
          05 WS-RESULT    PIC 9(04).          *> Result Variable
       01 WS-CALLING-PROG PIC X(08) VALUE "SUBPROG".

	   PROCEDURE DIVISION. 

	  * Calling subprogram dynamically with two inputs 
      * and receiving the result from SUBPROG
           CALL WS-CALLING-PROG 
		        USING BY REFERENCE 
				WS-INP1, WS-INP2, WS-RESULT.

           DISPLAY "INPUTS:  " WS-INP1 ", " WS-INP2.
           DISPLAY "RESULTS: " WS-RESULT.

           STOP RUN.

SUBPROG -

       ...
       DATA DIVISION.
       LINKAGE SECTION.
       01 LK-INP1      PIC 9(02).  *> To receive input1 from MAINPROG
       01 LK-INP2      PIC 9(02).  *> To receive input2 from MAINPROG
       01 LK-RESULT    PIC 9(04).  *> To send result to MAINPROG

	  * Receiving data from main program CALL statement
       PROCEDURE DIVISION USING LK-INP1, LK-INP2, LK-RESULT. 

           COMPUTE LK-RESULT = LK-INP1 * LK-INP2.
           GOBACK.

JCL -

//MATEPKRJ JOB MSGLEVEL=(1,1),NOTIFY=&SYSUID     
//*
//STEP01  EXEC PGM=MAINPROG                      
//STEPLIB  DD  DSN=MATEPK.COBOL.LOADLIB,DISP=SHR 
//SYSOUT   DD  SYSOUT=*

Output -

INPUTS:  47, 25
RESULTS:  1175

Explaining Example -

In the above example:

MAINPROG is the main program, and SUBPROG is the subprogram.
WS-INP1 and WS-INP2 are the inputs passed from MAINPROG to the SUBPROG. SUBPROG receives the data into LK-INP1, LK-INP2 from MAINPROG, multiplies those values, and places the result into LK-RESULT.
SUBPROG returns the output in LK-RESULT, and MAINPROG displays the result received from SUBPROG.