Book Review: Subfiles in Free-Format RPG

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Whether you're a newbie or a seasoned pro, this book has something for you.

Written by Mike Faust

For System i developers, mastering the ability to develop subfile applications is an absolute must! In Subfiles in Free-Format RPG, Kevin Vandever takes the reader through the subfile concept—from start to finish. Unlike other books on the topic, this one specifically focuses on coding subfile applications in free-format RPG and does an excellent job of explaining how to use subfiles in the modern rendition of the RPG language.

The author covers every aspect of the topic in a concise "hit the ground running" manner that lets the readers get their feet wet right away. Kevin starts out with the basic information on the subfile concept itself, which can be somewhat foreign at first glance. He gives simple examples of a display subfile to help the reader understand the concept. Later, the book delves into more advanced techniques like windowed subfiles, displaying multiple subfiles on a single screen, and even the use of IBM APIs to handle message subfiles. One of the things I liked most about this book was the fact that it contained easy-to-understand examples that are realistic representations of applications that a programmer might run into.

As icing on the cake, he even includes a chapter that covers a nifty little technique for how to combine embedded SQL in your free-format RPG program to create dynamically sorted subfile displays. In a later chapter, readers learn the unique challenges and benefits offered by utilizing subprocedures in subfile application programming. That same chapter covers the use of recursive calls to subprocedures to present multi-level hierarchical data in a subfile display. This technique alone is extremely valuable even for experienced software developers.          

Readers will also be pleasantly surprised to find free-format techniques that aren't specific just to subfile programming, but can be utilized in non-subfile programs as well. As a result, this book is not only a great resource on subfile display programming, but also a nice introduction to the free-format RPG language. This is a perfect book for entry-level programmers, but experienced software developers will also find this book to be a great resource.  The book is a complete "soup to nuts" guide to subfile display programming…and more.   

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