Using parent and child class in ooabap to add 2 numbers

*&---------------------------------------------------------------------*
*& Report  YSAP_PARENT_CHILD_CLASS1
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*

REPORT  ysap_parent_child_class1.

PARAMETERS : e TYPE i,
             f TYPE i.
*----------------------------------------------------------------------*
*       CLASS parentcls DEFINITION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS parentcls DEFINITION.
  PUBLIC SECTION.
    DATA : a TYPE i,
                 b TYPE i.
    METHODS: add.

  PROTECTED SECTION.
    DATA: c TYPE i.
ENDCLASS.                    "parentcls DEFINITION

*----------------------------------------------------------------------*
*       CLASS parentcls IMPLEMENTATION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS parentcls IMPLEMENTATION.
  METHOD add.
    a = e.
    b = f.
    c = a + b.
    WRITE: 'this is parent class data'.
    WRITE: c.
  ENDMETHOD.                    "add
ENDCLASS.                    "parentcls IMPLEMENTATION

*----------------------------------------------------------------------*
*       CLASS childcls DEFINITION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS childcls DEFINITION INHERITING FROM parentcls.
  PUBLIC SECTION.
    METHODS: add1.
ENDCLASS.                    "childcls DEFINITION

*----------------------------------------------------------------------*
*       CLASS childcls IMPLEMENTATION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS childcls IMPLEMENTATION.
  METHOD add1.
    WRITE: 'this is child class data'.
    WRITE: c.
  ENDMETHOD.                                                "add1
ENDCLASS.                    "childcls IMPLEMENTATION


START-OF-SELECTION.

  DATA: parent TYPE REF TO parentcls,
        child TYPE REF TO childcls.

  CREATE OBJECT: parent, child.

  CALL METHOD: parent->add.