Jim Martin comes through for us again.
Reviewed by Joe Pluta
Some time ago, I had the privilege of reviewing Jim Martin’s Functions in Free-Format RPG IV, and I was immediately struck by how Jim can take a complex subject and make it accessible to IBM i programmers. His newest book, Free-Format RPG IV, Third Edition, carries on that tradition wonderfully.
The book has a straightforward and logical flow. It starts with a brief description of prehistoric (that is, fixed-format) RPG followed by a great explanation of why you would want to move to the new free-format syntax. I particularly like that he moved this paragraph up in the book; I think it’s important that we as programmers can articulate to our peers and management the benefits of free-format syntax. It’s sometimes a difficult sell, especially among us old-timers, but Jim provides a cogent argument.
New Chapters: Specs and Embedded SQL
Jim has kept the book current with a couple of timely additions. The first is a section on the specifications other than the calculation specification (C-spec). Delivered as a technology refresh back in 2014, these new specifications took RPG nearly as far down the free-format path as it could go. The only specifications that don’t have free-format equivalents are program-described input and output specifications, and in my opinion they should never get them. I’m perfectly happy leaving my I- and O-specs in the past (and of course, you can always use fixed-format statements if you really need them).
The other is a brief but important chapter introducing the new syntax for embedded SQL. While this is not the focus of this book, I’m glad Jim took the time to at least present the topic because I consider the seamless merging of RPG and SQL to be perhaps the single most powerful capability of the language. The fact that you can intersperse SQL statements with all the standard capabilities of RPG (even including native I/O!) gives you as a programmer so much more versatility. I’d really like to see a Jim Martin book on embedded SQL programming!
But back to this book. Having made the case for free-format RPG, Jim proceeds to walk you through the syntax. He starts with an overview of the free-format language rules. If you’ve been a little hesitant to try the new syntax, this chapter will alleviate your fears as it explains the similarities and the differences between the two styles. This chapter contains a perfect example of why I like to read Jim Martin books: a brief note on the subject of case. Now, if you’re an old-school RPG programmer like me, you know that all code is in upper case as it was intended. But one brief paragraph is enough to get you thinking about the subject of case and why it might be important when naming your variables and procedures. Jim doesn’t profess to tell you how you should capitalize, but he does suggest that you need to consider it. Nuggets like this that expand your concept of the RPG language are sprinkled throughout the book.
After the introduction is the meat of the book: a step-by-step description of how to use free- format syntax to perform all your day-to-day programming functions. The book starts with I/O, because after all, if you have no I/O, your program isn’t really doing much. This medium-length chapter is followed by a similarly sized chapter on program flow that addresses the nuances of IF/ELSE/ENDIF and DO loops as well as the somewhat newer SELECT statement, which replaces the deprecated CASxx opcodes. The previously mentioned brief chapter on embedded SQL is followed by what is rightfully the longest chapter in the book: data manipulation.
Data manipulation is a term that encompasses a lot of things that we RPG programmers pretty much lump together in the MOVE instruction. The biggest change for programmers moving to free-format RPG is the fact that the MOVE instruction and its relatives MOVEL and MOVEA are no longer supported. There was considerable discussion about this when the original free-format C-spec syntax was introduced. While many of us argued heroically for some sort of support, in the end MOVE was removed from the language, relegated to the trash heap along with I- and O-specs. You’ll need to learn the new syntaxes provided by free-format RPG; Jim does an excellent job of going through them.
The rest of the explanatory part of the book is contained in the next two chapters. The first, on arithmetic operations, shows you how expressions can be used to combine multiple old-school RPG operations, as well as some syntactical sugar that helps reduce errors, especially with our new, longer variable names. The other chapter focuses on calling programs and procedures, and particularly prototypes, which are now free-format as well.
Real-World Code Examples
If that’s all there were to the book, it would be a good addition to any RPG programmer’s reference library. However, it is the rest of the book that marks it exclusively as a Jim Martin production. First is a chapter addressing specifically some of those issues I mentioned throughout the article, such as how to replace a MOVE with an EVAL, or what to do with those CASxx constructs. The next chapter provides several real-world examples of programs written entirely in free-format RPG. The programs are simple but solidly business-oriented and provide an opportunity to touch and feel real, working free-format RPG code. It’s this sort of action-oriented content that really makes Jim’s books so useful.
A few appendices round out the book: one on the opcodes, a second with all the source code for the examples, and a third listing the free-format alternative for fixed-format opcodes.
The Perfect Package
Taken together, these components deliver a great way to get started with free-format RPG, but I expect nothing less when I see Jim’s name on the cover.