Modularization in SAP ABAP

In SAP ABAP environment, modularization involves the organization of programs into modular units, also known as logical blocks. It reduce redundancy and increases program readability even as you are creating it and subsequently during the maintenance cycle.Modularization also enables reusability of the same code again.ABAP has made it necessary for developers to modularize, organizing the programs relatively more than in the OOPS based language that have relatively more built in modular feature.

Modularization techniques:

• Subroutines
• function module
• Include
• Field-symbol.

Subroutine: It is a mini program and can be called within program and from outside of the program.
Using Subroutines we can perform calculations, write statement, call function Module etc.

Types of Subroutine :

• Internal subroutine. 
• External subroutine.

Passing parameters in Subroutine:

• Pass by Value
• Pass by reference

Pass by Value:

DATA X TYPE C VALUE 'APPLE'.

PERFORM SUB USING X.

WRITE:/  X.

FORM SUB USING VALUE(P).

P = 'BAT'.

WRITE:/ P.

ENDFORM.

 Pass by reference

DATA X  TYPE C   VALUE 'A'.

PERFORM SUB CHANGING X.

WRITE:/  X.

FORM SUB CHANGING P.

P = 'B'.

WRITE:/ P.

ENDFORM.