calculator in plsql

I have created a simple calculator using concept of packages and functions in plsql

if there is any query you can comment below

create or replace package my_calci  as
function addition(a in number,b in number) return number;
function subtraction(a in number,b in number) return number;
function multiplication(a in number,b in number) return number;
function division(a in number,b in number) return number;
end my_calci;

create or replace package body my_calci as

function addition(a in number,b in number) return number is
 z number;
begin 
   z := a + b;
   return z;
end addition;
     

function subtraction(a in number,b in number) 
  return number 
  as
  z number;
begin 
   z := a - b;
   return z;
end subtraction;

function multiplication(a in number,b in number) return number as
 z number;
begin 
  z := a * b;
   return z;
end multiplication;

function division(a in number,b in number) return number as
 z number;
begin 
  z := a / b;
   return z;
end division;

end my_calci;


declare
ch varchar2(5);
input1 number;
input2 number;
output number;
begin
  input1 :=&Enter_no_1;
  input2 :=&Enter_no_2;
  ch :='&Enter_choice';
 case ch
   when '+' then
     output := my_calci.addition(input1,input2);
     dbms_output.put_line(output);

   when '-' then
     output := my_calci.subtraction(input1,input2);
     dbms_output.put_line(output);

   when '*' then
     output := my_calci.multiplication(input1,input2);
     dbms_output.put_line(output);

   when '/' then
     output := my_calci.division(input1,input2);
     dbms_output.put_line(output);
 else dbms_output.put_line('Wrong_input');

end case;
end;