Advantages of Subprograms

Subprograms provide extensibility; that is, they let you tailor the PL/SQL language to suit your needs. For example, if you need a procedure that creates new departments, you can easily write one, as follows:

PROCEDURE create_dept (new_dname VARCHAR2, new_loc VARCHAR2) IS
BEGIN
   INSERT INTO dept VALUES (deptno_seq.NEXTVAL, new_dname, new_loc);
END create_dept;

Subprograms also provide modularity; that is, they let you break a program down into manageable, well-defined modules. This supports top-down design and the stepwise refinement approach to problem solving.

In addition, subprograms promote reusability and maintainability. Once validated, a subprogram can be used with confidence in any number of applications. If its definition changes, only the subprogram is affected. This simplifies maintenance.

Finally, subprograms aid abstraction, the mental process of deriving a universal from particulars. To use subprograms, you must know what they do, not how they work. Therefore, you can design applications from the top down without worrying about implementation details. Dummy subprograms (stubs) allow you to defer the definition of procedures and functions until you test and debug the main program.