In V5R1, ILE RPG (RPG IV) was given a facelift with the addition of a free-format coding option. This option allows you to write the calculation (C) specs of your program without following the rigid positioning requirements of a standard RPG program and, for that matter, without the C! What you end up with is a programming language that is like a mix between RPG and C with a dash of Java thrown in. In this article, I'll examine what you can and can't do in free-format ILE RPG and how to make the most of this great programming alternative.

/free Your Mind

If you are running OS/400 V5R1 or higher, you already have what you need to use free-format ILE RPG. That's because the free-format option has become part of the language structure. A free-format block of code is defined by using the /free and /end-free compiler directives. This allows you to define some portions of a program using free-format code and other portions using standard ILE RPG code.

There are currently a few things that you can't do in free-format. One example is defining a key list (KLIST) to be used when chaining or reading from a file. The KLIST opcode and corresponding KFLD opcodes must be defined using standard ILE RPG C specs. It's also important to remember that the file (F) specs, definition (D) specs, and output (O) specs cannot be specified in free-format. The code shown in Figure 1 is a sample of free-format C specs.

Figure 1: This code is an example of free-format ILE RPG C specs.

The free-format section of the code starts with the /free compiler directive and ends with the /end-free compiler directive. As for the code that falls between these two directives, you'll notice some things that look familiar and some things that may not. First off, all free-format code must be specified between positions 8 and 80 on each line. You'll also notice that a semicolon is used to identify the end of each the statement. This is done to allow for statements to be longer than a single line. The C is also gone from the calculation specs. Compiler directives can be placed within free-format code, but it's important to remember that they cannot appear on a line with any operation codes. When using the /COPY or /INCLUDE compiler directives to include code from another source file, the compiler assumes that the copied code is in standard fixed-format RPG. This means that any free-format copybook source must begin and end with the /free and /end-free compiler directives.

The Code

In some cases, the free-format versions of the RPG opcodes may be coded differently from the fixed-format RPG. The free-format version of the IF statement works in pretty much the same way as the ILE RPG IF statement. In free-format, however, the condition portion of the statement is not limited to what can fit in the extended factor 2 field. The free-format CHAIN statement is used slightly differently from a standard ILE RPG CHAIN. In free-format, the chain command is used, as shown below:

In this sample, the E operation extender can be used to reset the state of the %ERROR and %STATUS built-in functions (BIFs) prior to performing a chain. The N operation extender is used on an update-capable disk file to disable record locking for this chain operation. Keyfield identifies either a single field or a key list name containing the search key value as would appear in factor 1 on a CHAIN in standard RPG. The file-or-record-name identifies the file name or record name to be chained to. This value would appear in factor 2 of a standard RPG statement. The optional data-structure name can be used with program-described files to place the record read into the defined data structure.

As with all of the free-format operation codes, the free-format CHAIN operation doesn't allow resulting indicators to be used. The %error and %found BIFs should be used in place of the resulting indicators for any file access opcodes (Chain, Read, etc.) When using free-format code, the eval and callp operations can be omitted. This means that either of the following statements can be used to set the value of the payment variable.

One circumstance where you will need to use the eval opcode is when you want to use an operation extender, such as the half-adjust extended (H), as shown below:

Just as with the eval opcode, the callp opcode can be omitted when calling a prototyped procedure. The free-format syntax allows for either of the lines of code shown below:

As this example shows, you must specify empty parentheses if no parameters are being passed. In addition to some other opcodes, for obvious reasons, the RPG arithmetic operation codes (ADD, SUB, MULT, DIV, MVR) are not supported in free-format. These can be replaced by the mathematic operators (+, -, *, /) along with the BIF %REM, which is used to replace the move remainder (MVR) opcode. In addition to these, the MOVE opcodes (MOVE, MOVEA, MOVEL) and COMP opcode are also not supported in free-format. The table in Figure 2 contains a list of the operations that are supported in free-format.

Figure 2: These opcodes are supported by free-format ILE RPG.

It's important to remember that resulting indicator use is not permitted in free-format. As with the chain example earlier, most operation codes that have result indicators in standard RPG can use a BIF in place of the result indicator. When using the any of the READ opcodes, the %EOF and %ERROR BIFs can be used in place of result indicators. Figure 3 shows a sample of the free-format code using READE operation.

Figure 3: This example shows how to use the free-format ILE READE opcode.

As with the chain opcode, the set low level key (setll) and read equal key (reade) opcodes are both used in the format:

This is actually the case with most of the ILE RPG opcodes available in free-format. The exception would be any opcodes that do not require one of the factors or the result field. Operands, including subroutine names, can be longer than the 14-character limit of standard ILE RPG. Because there is now a means by which to define a field within free-format, all field definitions must be done outside of the free-format code, using either standard RPG statements or D specifications. A single statement can be continued to multiple lines by simply omitting the semicolon character on all but the last line. Figure 4 shows a sample of a multi-line statement.

Figure 4: Free-format ILE RPG statements can run over multiple lines.

In this example, the value for the field TextDate is evaluated using the %substr BIF within one statement that runs over two lines of code. The evaluated value is then displayed to the session console using the dsply opcode.

An important consideration when moving from standard RPG or ILE RPG to free-format RPG is that conditioning indicators, as shown in the example below, can't be used:

While the use of conditioning indicators is frowned upon by many programmers, let's face it, you probably have a program running somewhere on your system that still uses this type of code. In free-format, this would be replaced by the section of code shown here:

This example replaces the conditioning indicator with an if statement that checks the state of the indicator *INKC, which indicates that the F3 key was pressed. While using this technique would be preferred in any version of RPG, in free-format it's absolutely required. This can be a consideration if you're planning to convert old applications to free-format.

Something Old, Something New

One nice thing about moving to the free-format RPG is that you can actually combine standard RPG statements with sections of free-format code. Figure 5 shows an example of mixing free-format and fixed-format ILE RPG code.

Figure 5: This sample combines free-format code with standard ILE RPG code.

This example uses the MOVE opcode to put the contents of the alphanumeric field DATEALPH into the numeric field DATENUM using standard-format ILE RPG code. A free-format if statement is then used along with a statement that evaluates a new value for the field DATENUM. In this example, you are also able to define the field length for DATENUMwithin the fixed-format code. As I mentioned earlier, this can't be done in free-format.

One of the advantages of being able to combine standard-format ILE RPG with free-format is that you can slowly convert a program to free-format, piece by piece. This allows you to change portions of the code and then compile and test them. This can make debugging problems with converted code much easier.

As I mentioned earlier, any copybook source is assumed to be fixed-format but can be identified as free-format using the /free and /end-free directives at the beginning and end of the copybook source. This allows you to maximize the use of existing code segments that are stored in copybook members while creating programs that use free-format code. This also means that if you convert existing copybook members to free-format code, standard ILE RPG programs that used the old versions will be able to use the new free-format version of the copybook by simply recompiling.

Another advantage to being able to combine standard ILE RPG and free-format ILE RPG is that it will allow you to make use of opcodes that are not supported in free-format, for example GOTO and TAG. If your program requires the use of these opcodes, other than redesigning the logic of your program, there really is no good alternative. The sample code shown in Figure 6 allows you to use the GOTO and TAG opcodes while still making use of free-format code.

Figure 6: This example mixes standard ILE RPG with free-format code.

While this example doesn't use "preferred" programming techniques, it illustrates the point.

What Else Is in V5R1 RPG?

Another feature that was added into ILE RPG in V5R1 that is not specific to free-format but does complement the free-format code nicely is the ability to use qualified field names with data structures. With this feature, you can to define the same field name within two data structures and reference the correct field in the same way that you would in SQL, C, or Java. This is accomplished through the use of two new keywords on the D specs. The QUALIFIED keyword defines that a data structure will be accessed using its qualified name. The LIKEDS(data structure name) keyword allows you to define a new data structure that has the same format as an existing data structure. Figure 7 shows an example of how this would appear in a program.

Figure 7: This sample code shows the use of qualified data structures.

This example illustrates the ability to access the fields within each of the data structures using the following format:

In addition to qualified data structures, the elseif opcode is an addition in V5R1 that, while not restricted to free-format, extends the usefulness of free-format ILE RPG. The elseif opcode allows you to reduce the number of nested if statements within your program. This opcode allows you to replace this code

with this much simpler code:

Not only does this method require fewer lines of code, but it makes analyzing the code a much simpler process.

V5R2 Changes and Additions

As if what I've covered already wasn't enough, in V5R2, IBM is offering even more enhancements to free-format ILE RPG. Not the least of these enhancements is the addition of the %KDS BIF. This function can be used with file opcodes (chain, read, etc.) in place of a key list, as shown below:

In this example, DSKEY is a data structure defined using the new LIKEREC keyword. This keyword allows you to create a data structure based on a record format. In the example here, the *KEY parameter is used to retrieve only the key field information from the specified file. Partial keys can be used by specifying a second parameter on the %KDS function that defines the number of key fields to be used, as shown here:

In this example, the first two key fields defined for the file would be used to retrieve the record. Alternatively, in V5R2, you can specify a list of fields in place of the key list name or %KDS BIF as shown here:

This example uses the three specified fields to retrieve the desired data from the file. You can specify partial keys by simply reducing the number of fields within the parentheses. When using either of these techniques in free-format code, another big change is that fields specified within the key have to be only the same type, not the same length. This means that if your file has a key field defined as a nine-position numeric field with no decimal places, you can chain to that file using a numeric field that is defined as 15 positions with five decimals.

Here's another example: If a file's key field is a 10-character alpha field, the key field specified in free-format could be a 12-character alpha field. You can't, however, use a numeric field for a key that is alpha or vice versa.

Another BIF that makes its debut in V5R2 is the %FIELDS BIF. This function is used with the update opcode and allows you to selectively update defined fields. The following example would be used to only update the fields fldate and fltime when the update operation is executed:

Mathematical operators have also been enhanced in V5R2 with the addition of +=, -=, *=, **= and /=. These operators can be used to perform the desired arithmetic function on the result field and another specified field or value. For example, instead of using

you can now specify this:

In either of these examples, the value of count is replaced with the value of count plus one. This method is similar to the arithmetic functions used in C or Java.

In addition to these, the %DEC, DECH, %FLOAT, %INT, INTH, %UNS, and %UNSH BIFs have been enhanced to allow the use of a character field as the parameter for the functions. This means that the example below is now acceptable:

This enhancement makes it easier to translate a character field to a numeric field.

Coloring Outside of the Lines

I hope I've helped to illustrate how free-format ILE RPG can make your programming tasks a lot easier. Once you've had a chance to try using free-format code on your system, you'll see how much fun it can be to color outside of the lines.

Mike Faust is the MIS Manager for The Lehigh Group in Macungie, PA. He has nearly 15 years of experience with midrange systems and personal computers. Be sure to check out Mike's book The iSeries and AS/400 Programmer's Guide to Cool Things from MC Press. Mike can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Mike Faust is a senior consultant/analyst for Retail Technologies Corporation in Orlando, Florida. Mike is also the author of the books Active Server Pages Primer, The iSeries and AS/400 Programmer's Guide to Cool Things, JavaScript for the Business Developer, and SQL Built-in Functions and Stored Procedures. You can contact Mike at This email address is being protected from spambots. You need JavaScript enabled to view it..

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