If you use the free-format specification, good standards will result automatically.
Editor's Note: This article is an excerpt from the book Programming in RPG IV, 4th Edition.
At current releases, RPG IV is primarily a free-format language, especially in the area of calculation processing. While it's not perfect, the free-format specification effectively renders the traditional fixed-format Calculation specification obsolete. IBM has introduced many new RPG IV features exclusively in free format.
The advantages of free format are well proven. It's easier to read, document, and maintain than fixed-format code, and its syntax is consistent with other modern computer languages. You should use it exclusively, especially when writing new programs or performing extensive maintenance on existing programs. In many cases, if you use the free-format specification, good standards will result automatically, because the free-format specification doesn't allow much of the obsolete baggage and poor practices that fixed-format C-specs allowed.
Avoid mixing fixed-form style and free-form style in your programs. The result is inconsistent and difficult to read. Take full advantage of the more natural order and expanded space afforded by the free-form specification.
Indent Code in Loops and Groups
When you're coding loops and groups, indent the code within a group by a couple of spaces to highlight the structure of the code group, as the following examples illustrate:
If %Found;
Eval(h) Totalpay = Regpay + Ovtpay;
Endif;
Select;
When Hours <=40;
Totalpay = Hours * Rate;
When Dblhours = 0;
Totalpay = (Hours * Rate) + ((Hours - 40) * Rate * 1.5);
Other;
Totalpay = (Hours * Rate) + ((Hours - 40) * Rate * 1.5) +
(Dblhours * Rate * 2);
Endsl;
Dou %Eof(Master);
Read(e) Master;
Select;
When %Eof(Master);
Leave;
When %Error;
Exsr Errsubr;
Other;
Exsr Process;
Endsl;
Enddo;
But don't completely abandon columnar alignment as a tool to aid readability in expressions. Especially when an expression must continue onto subsequent lines, align the expression to make it easier to understand:
Totalpay = (Reghours * Rate) +
(Ovthours * Rate * 1.5) +
(Dblhours * Rate * 2);
If your program includes embedded SQL statements, integrate the SQL completely by using the same indenting standards for the SQL statements that you use for the rest of the program:
If Instate = 'TX';
Pgmaccount = 'G5X67';
Exec SQL Select Firstname, Lastname, City, State
Into :Infirstname, :Inlastname, :Incity, :Instate
From Master
Where Account = :Pgmaccount;
Exsr Process;
Endif;
If the SQL statement is a long one, as in the above example, consider coding the individual SQL predicates on separate lines and aligning them as you would multiline expressions.
Use Mixed-Case Source
Closely related to using free-format syntax is the standard to use mixed uppercase and lowercase characters in the source code. Take advantage of this capability to make your program source easy to read. When coding a symbolic name, use mixed case to clarify the named item's meaning and use. Do not code in ALL UPPERCASE or all lowercase characters. Instead, use a logical combination of uppercase and lowercase, perhaps capitalizing each word in the code line:
Chain Postalcode Citymaster;
Another possibility is to use a notation commonly called "CamelCase," which joins compound words without spaces, capitalizing each section of the compound:
Chain PostalCode CityMaster;
If—but only if—your installation integrates Java programs into its applications, you might consider Java's traditional "Hungarian" notation, a variation of CamelCase in which the name of the variable indicates its type; the name begins with lowercase characters. Using Hungarian notation, the name "unsCounter" might indicate an unsigned integer, while "decAmount" might indicate a packed decimal number.
For RPG-reserved words and operations, as well as named constants, consider using ALL UPPERCASE characters. No matter which standard you use, be consistent.
Jim is the president and founder of imPower Technologies, where he provides professional IBM i training and consulting services. He is active in the IBM i community, working to help companies train their employees in the latest IBM technologies and develop the next generation of IBM i professionals.
MC Press books written by Jim Buck available now on the MC Press Bookstore.
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