This part of the book is where it all comes together. By now, you’ve learned the basics. You know about declaring and working with variables. You’re an expert on error handling and loop construction. Now it’s time to build an application—and you do that by constructing the building blocks, made up of procedures, functions, packages, and triggers, as described in Chapters 17 through 19.Chapter 20 discusses managing your PL/SQL code base, including suggestions for tuning and debugging that code.Chapter 21, entirely new in the fourth edition, covers I/O techniques for PL/SQL, from DBMS_OUTPUT (sending output to the screen) and UTL_FILE (reading and writing files) to UTL_MAIL (sending mail) and UTL_HTTP (retrieving data from a web page).