Function

Create or Replace Function f_CkSal(Amt Number)
Return Boolean 
Is
   Begin
      Return ( Amt Between 100 And 1000);
   End;                                 
/
Select * 
  From User_Source 
 Where Name = 'F_CKSAL';

Declare
   Sal   Number(8,2)  := &Salary;
   Flag  Boolean;
Begin
   Flag := F_CkSal(Sal);
   If Flag                    /* or "If Flag = True" */
      Then Dbms_Output.Put_Line ( Sal || ' Good' );
      Else Dbms_Output.Put_Line ( Sal || ' Bad'  );
   End If;
End;
/