Create Push Buttons in Application Tool Bar ABAP Interview Questions

How to create pushbuttons in application tool bar in case of selection-screen?

REPORT zsiva_test
MESSAGE-ID zprecot.
TABLES : afru.

TYPES : BEGIN OF ty_test,
ism01 LIKE afru-ism01,
END OF ty_test.
TABLES sscrfields.

SELECTION-SCREEN : BEGIN OF BLOCK b1 WITH FRAME TITLE text-001.
SELECT-OPTIONS : so_werks FOR afru-werks.
SELECTION-SCREEN PUSHBUTTON /79(10) charly USER-COMMAND abcd.
SELECTION-SCREEN END OF BLOCK b1.

INITIALIZATION.
MOVE 'Press' TO charly.

START-OF-SELECTION.

END-OF-SELECTION.

AT SELECTION-SCREEN.
IF sscrfields-ucomm = 'ABCD'.
MESSAGE i000 WITH so_werks-low 'Success' .
ENDIF.