8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 1/19

STATIC CALL AND DYNAMIC CALL

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 2/19

Objectives of Presentation1) Ways Of Transf erring control from one program to

another

2) Why we need to make a call3) What is Static and Dynamic Call

4) Making Static and Dynamic Calls

5) Example of Static and Dynamic Call

6) Performance of static and Dynamic Call

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 3/19

Ways Of Transf erring Control to the 

Sub ProgramTo enhance the performance of program we 

transf er the control from one program toanother

There are four ways by which we transf er the control to programs:

1) Static Calls

2) Dynamic calls

3) Calls to nested programs

4)Calls to dynamic link libraries( DLLs)

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 4/19

Why should we make a Call

A program(Main program) can also ref erence an independent sub-programs stored in a library using CALL.

Types of Calls:

1. Static Call

2. Dynamic Call

Advantages:1. Avoids Duplication of effort

2. Improves programmer productivity

3. Provides greater flexibility.

Syntax : Call literal/identif ier using parametersNOTE: Main program Calling program

Sub Program - Called program

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 5/19

How to make a Static Call Syntax: CALL literal  using param1 param2

literal-------Program-ID of Subprogram

using used to specif ies the parameters to be 

passed to the called program

In a Static Call the calling and all called 

programs are in the same load module.

Main Program(Calling Program)

Subprogram1(

(Called 

Program)

Subprogram2

(Called 

Program)

Subprogram3

(Called 

Program)Storage

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 6/19

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 7/19

Example for Static CallCalling Program

IDENTIFICATION DIVISION.

DATA DIVISION.

WORKING-STORAGE SECTION.

01 RECORD-2 PIC X.

01 RECORD-1.05 PAY PIC S9(5)V99.

05 HOURLY-RATE PIC S9V99.

05HOURS PIC S99V9. . .

PROCEDURE DIVISION.

1000-MAIN-PARA.CALL "SUBPROG" USING RECORD-1.

STOP RUN.

Called Program

IDENTIFICATION DIVISION.

PROGRAM-ID. SUBPROG.

DATA DIVISION.

LINKAGE SECTION.

01 PAYREC.10 PAY PIC S9(5)V99.

10 HOURLY-RATE PIC S9V99.

10 HOURS PIC S99V9.

PROCEDURE DIVISION USING PAYREC.

EXIT PROGRAM.

.

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 8/19

What happens in the static call

statements

When the control issued from the calling 

program

1. The control branches to the called programas it is available in the same load module of 

calling program.

2. Subsequent executions of the call statement 

make the called programs available in its last-

used.

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 9/19

What exactly happe s i  a static call?

CALL SUBPROG1 USING RECORD-1.

PROCEDURE DIVISION USING PAY-REC.

CALLING PROGRAM

SUBPROG1 SUBPROG2 SUBPROG3

RECORD-1

PAY-REC

Load lib

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 10/19

Subprogram Data Linkage

The order of the parameters is important as the sub-program recognizes them by relative location not by name.

Ex: Calling Program: CALL SUM-SUB USING AMT-1,AMT-2

Called Program: Procedure division using A, B.

Move zero to A or Move zero to AMT-1 will set the f ield in either case to zero ,because this 

statements are modif ied to Move zero to the f ield beginning at address 1000 (say that AMT-1 is starting at memory location 1000)

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 11/19

CALL OPTIONS

Syntax : CALL literal/identif ier using

by content param1,param2, by reference param 3,param4.

By Content---- Parameters should be passed BY CONTENT when you are not expecting 

them to get a value from the called program.

By Reference ---- Parameters should be passed BY REFERENCE if you require the called 

program to pass back data - as is the case with the result of  the multiplication.

Default : By ref errence

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 12/19

INITIAL VERB

As we know the subsequent issue of call will

branch to the sub-program in its previous 

state of execution.

To get the subprogram into its initial state  in a 

run unit or job we use the INITIAL attribute.

Syntax : Program-Id. P rogramname IS INITIAL

This will be explained with an example

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 13/19

Dynamic Call

Dynamic call: In this form of  a call statement, thecalled COBOL programs i s not link-edited with the

main program, instead link-edited into a separate

load module, and is loaded at runtime when it is

required( that is, when called).

Syntax : CALL identif ier using param1 param2

Main Program

Subprog

Load LibraryLoad library

Loading at runtime

Subprog

Call

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 14/19

Identif ication Division.

Program-Id. Mainprog.

Environment Division.

Data Division.

Working Storage Section.

77 ws-program name pic  x(8)

01 A pic 9(2).

01 B pic 9(2).

Procedure division.

Move Subprog1 to ws-program-name.

Call Subprog1 using A,B.

;;

Cancel ws-program-name.

Move Subprog2 to ws-program-name.

Call Subprog2 using A,B.

;;

Cancel ws-program-name

Stop Run.

Identif ication Division.

Program-ID. Subprog1.

Environment Division.

Data Division.

Linkage Section.01 subA pic 9(2).

01 subB pic 9(2).

Procedure Division using subA,subB.

Exit Program.

Identif ication Division.

Program-ID. Subprog2.

Environment Division.

Data Division.

Linkage Section.

01 subA pic 9(2).

01 subB pic 9(2).Procedure Division using subA,subB.

Exit Program.

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 15/19

Cancelling a Call

CANCEL statement is issued to cancel a sub-program.

When a cancel stmt is issued for a subprogram :

1) The storage occupied by the subprog is freed 2) Subsequent call to the subprogram functions as 

though it were a f irst call to the sub program.

Question:

Can we cancel a subprogram from a program otherthan the original caller?

Ans : Yes.

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 16/19

Subprogram1

Cancel Command

loaloaMain program Subprogram1

Cancel

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 17/19

Making A dynamic Call

Syntax : CALL IDENTIFIER  USING 

PARAM1,PARAM2.

ID

ENTIFIER VARIABLE NAME( SUBPRGRAMNAME).

Question: Can we make a dynamic call with 

static call syntax ?

Ans: Yes ,we can make a call by setting the 

compiler options as DYNM and NODLL.

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 18/19

Example Of dynamic ProgramCalling Program

IDENTIFICATION DIVISION.

PROGRAM-ID.MAIN-PROG.

DATA DIVISION.

WORKING-STORAGE SECTION.

77 PGM-NAME PIC X(8).

01 RECORD-2 PIC X .

01 RECORD-1.

05 PAY PICTURE S9(5)V99.

05 HOURLY-RATE PICTURE S9V99.

05 HOURS PICTURE S99V9. . . .

PROCEDURE DIVISION. . . .

MOVE "SUBPROG" TO PGM-NAME.CALL PGM-NAME USING RECORD-1.

CANCEL PGM-NAME.

MOVE "PAYMASTR" TO PGM-NAME.

CALL PGM-NAME USING RECORD-1 

RECORD-2.STOP RUN.

Called Program

IDENTIFICATION DIVISION.PROGRAM-ID. SUBPROG.

DATA DIVISION.

LINKAGE SECTION.

01 PAYREC.

10 PAY PICTURE S9(5)V99.

10 HOURLY-RATE PICTURE S 9V99.

10 HOURS PICTURE S 99V9.

77 PAY-CODE PICTURE 9.

PROCEDURE DIVISION USING PAYREC.

. . .

EXIT PROGRAM.

8/8/2019 Static and Dynamic Call

http://slidepdf.com/reader/full/static-and-dynamic-call 19/19

Performance Of static and Dynamic Call

Static Call

In static call, as the subprogram is link-edited with the main program, it is f aster in processing .So

static call is best when udon't need the services fordynamic calls

In static call the subprogramis link-edited with main 

program it occupies the main storage irrespective of the call issued on the subprogram.

Dynamic Call

In Dynamic Call, unless the call is issued the subprogram is not link-edited to the main program

So storage wise dynamic call are always better because they free 

the storage occupied by the dynamic call with a cancel stmt.

Dynamic calls are issued when we want to call many subprograms having a large storage.

Using a dynamic call stmt then cancel consecutively is always better than going for static call

occupying large amount of data