29
Fri, Nov
0 New Articles

RPG Academy: /FREE Your Code – What the Most-Used Operation Codes Look Like in Free-Format

RPG
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

It's time for a few more examples of free-format code, which help you memorize the coding rules and will speed up your transition to this new coding style.

The previous TechTip introduced the rules you need to abide by to write code in free-format and provided a simple example. This time around, I'll provide additional examples and discuss a few important things you'll need to keep in mind while coding in this new way.

Let's pick up where we stopped in the previous TechTip and look at another example of how indenting improves readability. The next code samples include instructions with code blocks inside other code blocks and also show how Factor 1, not used in the example from last time, is used in free format:

C     K_MYKEY     SETLL     MYFILE

C                 IF      %EQUAL

C     K_MYKEY     READE     MYFILE

C                 DOW       NOT %EOF(MYFILE)

C                 EXCEPT   DET_REC

C                 READ     MYFILE

C                 ENDDO

C                 ELSE

C                 EXCEPT   NoDet_REC

C                  ENDIF

Once again, this should be easy as pie in free format:

/FREE

SETLL K_MYKEY MYFILE;

IF %EQUAL;

   READE K_MYKEY MYFILE;

   DOW NOT %EOF(MYFILE);

     EXCEPT DET_REC;

     READ MYFILE;

   ENDDO;

ELSE;

   EXCEPT NoDet_REC;

ENDIF;

/END-FREE

The indentation makes the different code blocks more noticeable than ever, right?

In a fixed-format piece of code, having a sequence of nested IF statements makes it hard to understand where each of them ends:

C                 IF       P_Age >= 20 and P_Sex = 'F'

C                 EVAL     W_Code = 5

C                 ELSE

C                 IF       P_Age >= 20 and P_Sex = 'M'

C                 EVAL     W_Code = 4

C                 ELSE

C                  IF       P_Age >= 30 and P_Sex = 'F'

C                 EVAL     W_Code = 10

C                 ELSE

C                 IF       P_Age >= 30 and P_Sex = 'M'

C                 EVAL     W_Code = 9

C                 ELSE

C                 EVAL    W_Code = 20

C                 ENDIF

C                 ENDIF

C                 ENDIF

C                 ENDIF

You can replace those ELSE/IF blocks of lines by a single ELSEIF to make it more readable:

C                 IF       P_Age >= 20 and P_Sex = 'F'

C                 EVAL     W_Code = 5

C                 ELSEIF   P_Age >= 20 and P_Sex = 'M'

C                 EVAL     W_Code = 4

C                 ELSEIF   P_Age >= 30 and P_Sex = 'F'

C                 EVAL     W_Code = 10

C                ELSEIF   P_Age >= 30 and P_Sex = 'M'

C                 EVAL     W_Code = 9

C                 ELSE

C                 EVAL     W_Code = 20

C                 ENDIF

It's certainly an improvement over all those sets of ELSE followed by IF, but if there is more than one instruction after the ELSEIF, it can still get a bit confusing. That doesn't happen in free-format, assuming that the proper indentation is used:

/FREE

IF P_Age >= 20 and P_Sex = 'F';

   W_Code = 5;

ELSEIF P_Age >= 20 and P_Sex = 'M';

   W_Code = 4;

ELSEIF P_Age >= 30 and P_Sex = 'F';

   W_Code = 10;

ELSEIF P_Age >= 30 and P_Sex = 'M';

   W_Code = 9;

ELSE;

   W_Code = 20;

ENDIF;

/END-FREE

Personally, I think a SELECT block is clearer than an IF/ELSEIF block. As long as you use proper indentation, either of the two solutions works, but I still prefer this:

/FREE

SELECT;

   WHEN P_Age >= 20 and P_Sex = 'F';

     W_Code = 5;

   WHEN P_Age >= 20 and P_Sex = 'M';

     W_Code = 4;

   WHEN P_Age >= 30 and P_Sex = 'F';

     W_Code = 10;

   WHEN P_Age >= 30 and P_Sex = 'M';

     W_Code = 9;

   OTHER;

     W_Code = 20;

ENDSL;

/END-FREE

Don't worry about the missing EVAL operation codes; I'll get to that in a minute. Now, let's go back to the READE example from earlier to explain something I missed:

READE K_MYKEY MYFILE;

Notice how the READE line is written:

<Operation Code> <Factor 1> <Factor 2>

That's different from the usual format:

<Factor 1> <Operation Code> <Factor2>

This is just one of the things you need to get used to.

There are other things that might confuse you, such as the fact that EVAL and CALLP are optional, except when you need to use their extenders. You probably noticed this in the IF/ELSEIF example I just presented. The missing EVALs will seem a bit alien at first, but you'll eventually get used to it!

Not everything is "strange." Let me show you something that you'll certainly like. Here's a typical fixed-format piece of code:

C     K_MYKEY     CHAIN     MYFILE

C                 IF       %FOUND(MYFILE)

C                 EXSR     CustFound

C                 ELSE

C                 EXSR     NoCust

C                 ENDIF

Now, let's take advantage of the possibility of having longer names to make this clearer in free-format:

/FREE

CHAIN KEY MYFILE;

IF %FOUND(MYFILE);

   EXSR Customer_Found;

ELSE;

   EXSR Customer_Not_Found;

ENDIF;

/END-FREE

You have to admit that Customer_Not_Found is clearer than NoCust. This can be made even clearer with a few comments:

/FREE

CHAIN KEY MYFILE;

IF %FOUND(MYFILE);

   EXSR Customer_Found; // Retrieve customer info

ELSE;

   EXSR Customer_Not_Found; // Fill fields with N/A

ENDIF;

/END-FREE

Unlike in fixed-format, where comments need a line for themselves, in free-format you can mix code and comment in the same line, which allows for more precise and unobtrusive documentation. This is also an interesting approach to "modern" languages, where this in-line commenting is common.

Speaking of modern languages, here's something else that might be a bit confusing: you remember this line from the EVAL example, right? This code…

C                 EVAL     W_Some_Number = W_Some_Number + 1

…became this:

W_Some_Number = W_Some_Number + 1;

Well, there's another, shorter notation in free-format that RPG got from "modern" languages:

W_Some_Number += 1;

You'll find this particular form (+= 1) frequently in counter variables. This is called compound assignment, and you can use it with the following operators:

  • target += expression: The expression is added to the target.
  • target -= expression: The expression is subtracted from the target.
  • target *= expression: The target is multiplied by the expression.
  • target /= expression: The target is divided by the expression.
  • target **= expression: The target is assigned the target raised to the power of the expression.

For instance, the following cuts W_Some_Number in half:

W_Some_Number /= 2

I hope that you're now convinced, ready, and willing to start converting your code to free-format. It's an easy process, but there are some pitfalls. The next TechTips will provide valuable information on how you can start converting your code and finally leave one of the biggest anachronisms of RPG behind!

Rafael Victoria-Pereira

Rafael Victória-Pereira has more than 20 years of IBM i experience as a programmer, analyst, and manager. Over that period, he has been an active voice in the IBM i community, encouraging and helping programmers transition to ILE and free-format RPG. Rafael has written more than 100 technical articles about topics ranging from interfaces (the topic for his first book, Flexible Input, Dazzling Output with IBM i) to modern RPG and SQL in his popular RPG Academy and SQL 101 series on mcpressonline.com and in his books Evolve Your RPG Coding and SQL for IBM i: A Database Modernization Guide. Rafael writes in an easy-to-read, practical style that is highly popular with his audience of IBM technology professionals.

Rafael is the Deputy IT Director - Infrastructures and Services at the Luis Simões Group in Portugal. His areas of expertise include programming in the IBM i native languages (RPG, CL, and DB2 SQL) and in "modern" programming languages, such as Java, C#, and Python, as well as project management and consultancy.


MC Press books written by Rafael Victória-Pereira available now on the MC Press Bookstore.

Evolve Your RPG Coding: Move from OPM to ILE...and Beyond Evolve Your RPG Coding: Move from OPM to ILE...and Beyond
Transition to modern RPG programming with this step-by-step guide through ILE and free-format RPG, SQL, and modernization techniques.
List Price $79.95

Now On Sale

Flexible Input, Dazzling Output with IBM i Flexible Input, Dazzling Output with IBM i
Uncover easier, more flexible ways to get data into your system, plus some methods for exporting and presenting the vital business data it contains.
List Price $79.95

Now On Sale

SQL for IBM i: A Database Modernization Guide SQL for IBM i: A Database Modernization Guide
Learn how to use SQL’s capabilities to modernize and enhance your IBM i database.
List Price $79.95

Now On Sale

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: