Opening Up a New RPG World

Four vendors offer immediate Open Access solutions


IBM just announced Rational Open Access: RPG Edition. This new program product from IBM opens the interface to the RPG language. This move has prompted many good questions: What does this mean? How does it work? What does it do?

What Does This Mean?

IBM has opened the RPG interface to allow programmers to extend the user experience beyond those available in previous releases of RPG. Application programmers will be able to direct RPG IV to explicitly send data to interfaces other than the traditional 5250 telnet, including graphical, Web, hand-held and XML, to name but a few. The solutions will be limitless once programmer imagination and modern coding techniques are applied to business applications.

How Does It Work?

Rational Open Access: RPG Edition has three pieces to the puzzle—the RPG program, the handler(s) for each data transfer and the program that will render the result. For simplicity, let’s explore the rendering of a new image by looking at the three pieces.

1) The RPG program. This must be an RPG IV program that will tell the compiler and the runtime that it won’t be using the standard file handlers from the operating system, by selecting a new keyword in the F specification.

2) A handler program. Consider the handler program the “data catcher.” This code will take the buffer of information from the RPG program, massage it as necessary and hand it over to the rendering program.

3) The rendering program. Different devices have various support requirements. For example, a blackberry uses a different language from an iPhone, which is different again from the languages of the Web. There needs to be a program to massage data, format it and display it in a way that makes sense for the specific device.

Just to put this all into context, the process is very similar to how things work with a green screen. The difference, of course, is who provides the pieces. An idea of how things work under the covers in RPG can set the scene for better understanding of IBM Rational Open Access: RPG Edition.

Traditionally, the RPG language has been tied to other components of the IBM i operating system, including runtime instruction sets and display file objects. When a programmer coded a WRITE operation to a file (data or display), under the covers many other coded components were being used. Using simple, high-level terms, let’s review the steps that take place. The WRITE operation causes the program buffer to be handed to the operating system’s data manager. The OS merges the data into the DDS Display file objects, creating a 5250 datastream, which would be handed to the display manager of the operating system, which in turn is written to a non-programmable terminal. In many ways, this combination of RPG runtime and OS instructions is similar to using a handler and a rendering program. This tight association has allowed programmers to remain above the technical operating system details and know that simply executing a WRITE operation renders the desired 5250 image.


Alison Butterill is the Power Systems application development offering manager and a senior consulting certified IT specialist.



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