create or replace procedure swap( num1 in out integer,num2 in out integer)
Is 
 temp integer:=0;

begin 
    temp:=num1;
    num1:=num2;
    num2:=temp;  
end;
/
declare 
  a integer:=&a;
  b integer:=&b;
begin 
  dbms_output.put_line('Before swaping '||a||'  '||b);
  swap(a,b);
   dbms_output.put_line('After swaping '||a||'  '||b);

end;
/