SQL> 
SQL> -- Private functions or procedures are defined only in the package body.
SQL> -- They are not defined in the package.
SQL> -- Suppose you would like to put all the private functions at the bottom
SQL> -- of the package (even though this is not required), or you would like to arrange
SQL> -- the sub routines in a particular order, how do you call a routine before it is defined?
SQL> -- You can not. But you can use "Forward declarations" in the package body to
SQL> -- get around the problem.
SQL> 
SQL> create or replace package test_pkg_a as
  2  function func2(p1 number) return number;
  3  end test_pkg_a ;
  4  /

Package created.

SQL> 
SQL> -- PLS-00313: 'FUNC4' not declared in this scope
SQL> create or replace package body test_pkg_a as
  2  function func2(p1 number) return number
  3  is
  4  begin
  5    return func4(p1)+10;
  6  end;
  7  
  8  function func4(p1 number) return number
  9  is
 10  begin
 11    return p1+4;
 12  end;
 13  
 14  end;
 15  /

Warning: Package Body created with compilation errors.

SQL> 
SQL> -- Forward declare func3
SQL> -- Note that function func3 and func1 are private functions
SQL> create or replace package body test_pkg_a as
  2  
  3  function func3(p1 number) return number;
  4  
  5  function func1(p1 number) return number
  6  is
  7  begin
  8    return p1+1;
  9  end;
 10  
 11  function func2(p1 number) return number
 12  is
 13  begin
 14    return func1(p1)+func3(p1)+2;
 15  end;
 16  
 17  function func3(p1 number) return number
 18  is
 19  begin
 20    return p1+3;
 21  end;
 22  
 23  end;
 24  /

Package body created.

SQL> 
SQL> select test_pkg_a.func2(10) from dual;

TEST_PKG_A.FUNC2(10)                                                            
--------------------                                                            
                  26                                                            

SQL> 
SQL> drop package test_pkg_a;

Package dropped.

SQL> 
SQL> spool off