call

CALL CALL VerbVerb

A COBOL statement for accessing a subprogram.A COBOL statement for accessing a subprogram.

Called programCalled program is a subprogram or program called is a subprogram or program called into a user program as needed.into a user program as needed.

Calling programCalling program is a program that calls a subprogram. is a program that calls a subprogram.

CALL SyntaxCALL Syntax

Call Call ParametersParameters

1. PROGNAME IDENTIFIER OR LITERAL1. PROGNAME IDENTIFIER OR LITERAL

It is possible not to specify the name of the called It is possible not to specify the name of the called subprogram as an explicit literal, as the following subprogram as an explicit literal, as the following example:example:

If response=“M” If response=“M”

move “MONTHLY” to sub-namemove “MONTHLY” to sub-name

elseelse

move “QUARTERLY” to sub-name.move “QUARTERLY” to sub-name.

CALL sub-name.CALL sub-name.


USING BY CONTENT/REFERENCEUSING BY CONTENT/REFERENCE

1. BY REFERENCE1. BY REFERENCE This clause may be omitted, in which case it is This clause may be omitted, in which case it is

specified by default.specified by default. Means to associate subprogram data-names in the Means to associate subprogram data-names in the

linkage and procedure division using… linkage and procedure division using… specifications with the address of the specifications with the address of the corresponding data-names in the calling program.corresponding data-names in the calling program.


USING BY CONTENT/REFERENCEUSING BY CONTENT/REFERENCE

2. BY CONTENT2. BY CONTENT The CALL statement makes available to the The CALL statement makes available to the

subprogram the content of the data-names listed in subprogram the content of the data-names listed in the CALL statement.the CALL statement.

The subprogram then does not make reference to The subprogram then does not make reference to the actual data-name storage locations in the the actual data-name storage locations in the calling program and cannot alter the contents of the calling program and cannot alter the contents of the data-names in the calling program.data-names in the calling program.

The calling program passes data, not references, to The calling program passes data, not references, to the called program.the called program.

CALL “STATS” USING BY CONTENT NO-OF-RECS,CALL “STATS” USING BY CONTENT NO-OF-RECS,

SALES-SALES-TABLE.TABLE.

CALL CALL Example.Example.

IDENTIFICATION DIVISION.IDENTIFICATION DIVISION.PROGRAM-ID DateValidate IS INITIAL.PROGRAM-ID DateValidate IS INITIAL.DATA DIVISION.DATA DIVISION.WORKING-STORAGE SECTION.WORKING-STORAGE SECTION. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

LINKAGE SECTION.LINKAGE SECTION.01 DateParam PIC X(8).01 DateParam PIC X(8).01 DateResult PIC 9.01 DateResult PIC 9.

PROCEDURE DIVISION USING DateParam, DateResult.PROCEDURE DIVISION USING DateParam, DateResult.Begin. Begin. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? EXIT PROGRAM.EXIT PROGRAM.

??????.??????. ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ?

CALL "DateValidate"CALL "DateValidate"USING BY CONTENT TempDateUSING BY CONTENT TempDateUSING BY REFERENCE DateCheckResult.USING BY REFERENCE DateCheckResult.

CALL CALL ParametersParameters

CALL "ProgramName" USING P1, P2, P3, P4.CALL "ProgramName" USING P1, P2, P3, P4.

PROCEDURE DIVISION USING P2, P4, P1, P3.PROCEDURE DIVISION USING P2, P4, P1, P3.

CALL CALL ParametersParameters

CALL "ProgramName" USING P1, P2, P3, P4.CALL "ProgramName" USING P1, P2, P3, P4.

PROCEDURE DIVISION USING P2, P4, P1, P3.PROCEDURE DIVISION USING P2, P4, P1, P3.

Positions Correspond - Not NamesPositions Correspond - Not NamesPositions Correspond - Not NamesPositions Correspond - Not Names

Parameter Passing Parameter Passing MechanismsMechanisms

CALL .. BYCALL .. BYREFERENCEREFERENCE

CALLedCALLedProgramProgram




Address of Address of

Data ItemData Item

DirectionDirectionof Data Flowof Data Flow





Data ItemData Item

CALL .. BYCALL .. BYCONTENTCONTENT


Copy ofCopy ofData ItemData Item






Data ItemData Item

CALL .. BYCALL .. BYCONTENTCONTENT


Copy ofCopy ofData ItemData Item

Address of Address of CopyCopy

Data Data ItemItem




ON OVERFLOWON OVERFLOW This conditional specifies execution of imperative-This conditional specifies execution of imperative-

statement-1 if the CALL cannot be executed statement-1 if the CALL cannot be executed because of insufficient storage, and the like.because of insufficient storage, and the like.

END-CALLEND-CALL This is a scope terminator that can be used as This is a scope terminator that can be used as

follows:follows:if N>zeroif N>zero

call “STATS” using…call “STATS” using…

on overflowon overflow

perform abcperform abc

move a to zmove a to z

end-callend-call

end-if.end-if.

Called Program Called Program RequirementsRequirements

1. 1. PROGRAM-IDPROGRAM-ID In the calling program, we code In the calling program, we code CALL ‘literal-1’ USING …CALL ‘literal-1’ USING … In the called program, we code In the called program, we code PROGRAM-ID. literal-1.PROGRAM-ID. literal-1. With COBOL 85, the PROGRAM-ID paragraph of the called With COBOL 85, the PROGRAM-ID paragraph of the called

program may have the following program may have the following INITIAL PROGRAMINITIAL PROGRAM clause: clause:

PROGRAM-ID. Program-name [IS PROGRAM-ID. Program-name [IS INITIALINITIAL PROGRAM]. PROGRAM].

If this clause is used, the called program will be restored to its If this clause is used, the called program will be restored to its initial state each time it is called.initial state each time it is called.

This means that all identifiers in Working-storage will contain This means that all identifiers in Working-storage will contain their original values, as specified by their VALUE clauses, before their original values, as specified by their VALUE clauses, before and after each call.and after each call.


2. 2. LINKAGE SECTIONLINKAGE SECTION

A Linkage Section must be defined in the called A Linkage Section must be defined in the called program for identifying those items that:program for identifying those items that:

(1) will be passed to the called program from the (1) will be passed to the called program from the calling program calling program

(2) passed back from the called program to the calling (2) passed back from the called program to the calling program.program.

The Linkage Section, if used, is coded after the File The Linkage Section, if used, is coded after the File and Working-storage Sections of the called program. and Working-storage Sections of the called program.

Similar to the Working-storage Section except that Similar to the Working-storage Section except that VALUE clauses for initializing fields are not permitted VALUE clauses for initializing fields are not permitted in the Linkage Section.in the Linkage Section.


3. 3. PROCEDURE DIVISION USINGPROCEDURE DIVISION USING The identifiers specified in the USING clause in the PROCEDURE The identifiers specified in the USING clause in the PROCEDURE

DIVISION entry include all fields defined in the LINKAGE DIVISION entry include all fields defined in the LINKAGE SECTION; these identifiers will be passed from one program to SECTION; these identifiers will be passed from one program to the other.the other.

They passed to and from corresponding identifiers in the CALL … They passed to and from corresponding identifiers in the CALL … USING of the main program.USING of the main program.

4. 4. EXIT PROGRAMEXIT PROGRAM The last executed statement in the called program must be the The last executed statement in the called program must be the

EXIT PROGRAM. EXIT PROGRAM. It signals the computer to return control back to the calling It signals the computer to return control back to the calling

program.program.

Avoiding “State Avoiding “State Memory” - The IS INITIAL Memory” - The IS INITIAL phrase.phrase.

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. Steadfast IS INITIALIS INITIAL.

DATA DIVISION.WORKING-STORAGE SECTION.01 RunningTotal PIC 9(7) VALUE 50.

LINKAGE SECTION.01 ParamValue PIC 99.

PROCEDURE DIVISION USING ParamValue.Begin. ADD ParamValue TO RunningTotal. DISPLAY "Total = ", RunningTotal. EXIT PROGRAM.

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. Steadfast IS INITIALIS INITIAL.




1212

Total = 62Total = 62

55


1212


Avoiding “State Memory” Avoiding “State Memory” - The IS INITIAL phrase.- The IS INITIAL phrase.

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. Fickle.








1212


55


1212


The CANCEL The CANCEL command.command.









1212


1212


CALL "Fickle" USING BY CONTENT IncValue.CALL "Fickle" USING BY CONTENT IncValue.CANCELCANCEL "Fickle""Fickle"CALL "Fickle" USING BY CONTENT IncValue.CALL "Fickle" USING BY CONTENT IncValue.

Question?Question?

1. When subprograms are used, there must be one and 1. When subprograms are used, there must be one and only one ____ program but there may be several ____.only one ____ program but there may be several ____.

MAIN;SUBPROGRAMMAIN;SUBPROGRAM

2. The statement that terminates execution of the 2. The statement that terminates execution of the subprogram and returns execution to the statement subprogram and returns execution to the statement following the corresponding CALL statement is the ___ following the corresponding CALL statement is the ___ command.command.

EXIT PROGRAMEXIT PROGRAM

3. A called subprogram [can/cannot] itself include a CALL 3. A called subprogram [can/cannot] itself include a CALL statement that results in execution of another statement that results in execution of another subprogram. subprogram.

CanCan

4. A called subprogram [can/cannot] itself include a CALL 4. A called subprogram [can/cannot] itself include a CALL statement that results in execution of the main program.statement that results in execution of the main program.

CannotCannot

Question?Question?

5. Because each subprogram has its own DATA DIVISION, 5. Because each subprogram has its own DATA DIVISION, and yet there are data that are to be used in both the and yet there are data that are to be used in both the main program and subprogram, the DATA DIVISION of main program and subprogram, the DATA DIVISION of the subprogram must include a special ____ SECTION the subprogram must include a special ____ SECTION to identify such data.to identify such data.

LINKAGE LINKAGE

6. For data that are used in both main program and 6. For data that are used in both main program and subprogram, the data names [must/need not] be the subprogram, the data names [must/need not] be the same in the two programs.same in the two programs.

Need notNeed not

7. For shared data items, what is important in the LINKAGE 7. For shared data items, what is important in the LINKAGE SECTION is the ___ description for each data-name.SECTION is the ___ description for each data-name.

PIC PIC

8. For shared data items, the order of the data-names in 8. For shared data items, the order of the data-names in the LINKAGE SECTION [is/is not] relevant.the LINKAGE SECTION [is/is not] relevant.

Is notIs not

Contained Sub-Contained Sub-ProgramsPrograms

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. MainProgram. ? ? ? ? ? ? ? ? ?01 TableItem IS GLOBALIS GLOBAL.

PROCEDURE DIVISION. ? ? ? ? ? ? ? ? ? CALL PutToTable USING BY CONTENT DataItem ? ? ? ? ? ? ? ? ? CALL ReportFromTable. EXIT PROGRAM.

IDENTIFICATION DIVISION.PROGRAM-ID. PutToTable. ? ? ? ? ? ? ? ? ?END-PROGRAM PutToTable.

IDENTIFICATION DIVISION.PROGRAM-ID. ReportFromTable. ? ? ? ? ? ? ? ? ?END-PROGRAM ReportFromTable.END-PROGRAM MainProgram.













Contained Sub-Contained Sub-ProgramsPrograms

The COMMON PROGRAM The COMMON PROGRAM PhrasePhrase

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. MainProgram. ? ? ? ? ? ? ? ? ?01 TableItem IS GLOBALIS GLOBAL.PROCEDURE DIVISION. ? ? ? ? ? ? ? ? ? EXIT PROGRAM.

IDENTIFICATION DIVISION.PROGRAM-ID. PutToTable. ? ? ? ? ? ? ? ? ? CALL ReportFromTable. ? ? ? ? ? ? ? ? ? END-PROGRAM PutToTable.

IDENTIFICATION DIVISION.PROGRAM-ID. ReportFromTable IS COMMON PROGRAM. ? ? ? ? ? ? ? ? ? CALL PutToTable USING ???? ? ? ? ? ? ? ? ? ? END-PROGRAM ReportFromTable.END-PROGRAM MainProgram.











YESYES








YESYES

NONO

Creating Abstract Data Creating Abstract Data Types?Types?

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. Stack.DATA DIVISION.WORKING-STORAGE SECTION.01 StackHolder IS GLOBAL. 02 StackItem OCCURS 20 TIMES PIC X(10).PROCEDURE DIVISION USING ????.Begin. EVALUATE TRUE WHEN PushStack CALL "Push" USING ??? WHEN PopStack CALL "Pop" USING ??? END-EVALUATE. EXIT PROGRAM.

IDENTIFICATION DIVISION.PROGRAM-ID. Push. ? ? ? ? ? ? ? ? ?END-PROGRAM Push.

IDENTIFICATION DIVISION.PROGRAM-ID. Pop. ? ? ? ? ? ? ? ? ?END-PROGRAM Pop.END-PROGRAM Stack.

$ SET SOURCEFORMAT"FREE"IDENTIFICATION DIVISION.PROGRAM-ID. Stack.DATA DIVISION.WORKING-STORAGE SECTION.01 StackHolder IS GLOBAL. 02 StackItem OCCURS 20 TIMES PIC X(10).PROCEDURE DIVISION USING ????.Begin. EVALUATE TRUE WHEN PushStack CALL "Push" USING ??? WHEN PopStack CALL "Pop" USING ??? END-EVALUATE. EXIT PROGRAM.

IDENTIFICATION DIVISION.PROGRAM-ID. Push. ? ? ? ? ? ? ? ? ?END-PROGRAM Push.

IDENTIFICATION DIVISION.PROGRAM-ID. Pop. ? ? ? ? ? ? ? ? ?END-PROGRAM Pop.END-PROGRAM Stack.

StackStack

PushPush

PopPop

MainMain

The IS EXTERNAL The IS EXTERNAL phrase.phrase.

FD CommonFileArea IS EXTERNAL.

WORKING-STORAGE SECTION.01 SharedRec IS EXTERNAL. 02 PartA PIC X(4). 02 PartB PIC 9(5).



ProgramAProgramA

01 SharedRec etc01 SharedRec etc

ProgramDProgramDProgramCProgramC01 SharedRec etc01 SharedRec etc

ProgramBProgramB

SharedRecSharedRec

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ProgramAProgramA



ProgramBProgramB

SharedRecSharedRecPUTPUT

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ProgramAProgramA



ProgramBProgramB

SharedRecSharedRecPUTPUT GETGET

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call

Technology

calling program

exit program

program requirements

user program

program foridentifying

main program

programid datevalidate

programid paragraph