Example of POP UP CALCULATOR in ABAP

REPORT  ZPOPUPCALCULATOR.

DATA: X_VALUE(15) TYPE C.

call function 'FITRV_CALCULATOR'

  IMPORTING
    OUTPUT_VALUE               = X_VALUE
  EXCEPTIONS
    INVALID_INPUT              = 1
    CALCULATION_CANCELED       = 2
    OTHERS                     = 3.

IF SY-SUBRC = 0.
   WRITE:/ 'Output IS: ', X_VALUE.
ENDIF.