SUBPROGRAM PACKAGE

PL/SQL package is a group of related functions, procedures, types, cursors, etc. PL/SQL package is like a library once written stored in the Oracle database and can be used by many applications.
A PL/SQL package has two parts: package specification and package body.
A package specification is the public interface of your applications. The public means the stored function, procedures, types, etc., are accessible from other applications.
A package body contains the code that implements the package specification.
Creating PL/SQL Package Specification
The package specification is required when you create a new package. The package specification lists all the objects which are publicly accessible from other applications. The package specification also provides the information that developers need to know in order to use the interface. In short, package specification is the package’s API.
If the package specification does not contain any stored functions, procedures and no private code is needed, you don’t need to have a package body. These packages may contain only type definition and variables declaration. Those variables are known as package data. The scope of package data is global to applications. It is recommended that you should hide as much as package data as possible and use get and set functions to read and write that data. By doing this, you can prevent your package data changed unintentionally.
It is important to note that you must compile the package specification before package body.
Here is the syntax for creating PL/SQL package specification:
CREATE [OR REPLACE] PACKAGE package_name
[ AUTHID { CURRENT_USER | DEFINER } ]
{ IS | AS }