What is RPG modernization?

These applications run on IBM i, the successor to the OS/400 operating system that originally ran on the AS/400 platform.

Modernizing RPG can involve a few things: refreshing the user interface, cleaning up the code, translating it into newer languages, connecting it to other software through APIs or moving it to the cloud. Whatever the approach, the ultimate aim is to preserve software that still works while making it current—work that falls under the broader headings of application modernization and legacy code migration.

RPG is one of the oldest programming languages still in daily commercial use. IBM created it in 1959 for the IBM 1401 computer, where it replaced punched-card processing and generated business reports—the origin of its name, as author Nick Litten relates in “A Brief History of the IBM RPG Programming Language.” For decades it has handled payroll, inventory and invoicing for banks, insurers, manufacturers and retailers.

The language evolved over the years. RPG II, the version of the 1960s and 1970s, was somewhat rigid—programmers entered code in fixed columns and relied on a built-in processing loop. RPG III, introduced with the System/38 in 1979, added structured building blocks—conditional tests, loops and reusable subroutines that programmers had come to expect. IBM rebranded it RPG/400 when the AS/400 launched in 1988, according to Wikipedia.

RPG IV, introduced in the mid-1990s, is the modern version of RPG used on IBM i systems. It became part of IBM’s Integrated Language Environment, which let RPG work more easily alongside other business languages such as COBOL and C. Since then, IBM has steadily modernized RPG, moving it away from its old rigid, column-based format. Today’s RPG—often called RPGLE or ILE RPG—can be written in a free-form style that looks much more like ordinary modern code than the RPG of decades past.

What exactly constitutes “modern RPG”? Modernizing RPG applications—work often grouped under the broader banner of IBM i modernization—can be either cosmetic or deep.

On the cosmetic side is user-interface modernization: replacing the text-only “green screen”—the green-on-black terminal display of classic IBM i applications—with a web or mobile interface, while leaving the underlying logic intact. It is often the quickest and most visible improvement. A similar approach involves leaving RPG in place but wrapping its business logic as web services—APIs that let modern applications call the old code’s functions and data.

A deeper approach is code refactoring: improving the structure of the code without changing what it does—converting fixed-format RPG to free-format, breaking large programs into smaller modules and replacing older database definitions with SQL, according to Litten. IBM’s AI coding agent IBM Bob can be extended with IBM i-specific knowledge to assist with this task.

The most pressing reason this work has become urgent is human rather than technical. The programmers who built these systems are retiring, and RPG is rarely taught in universities, so the supply of replacement coders is dwindling. “RPG programming is a disappearing skill; by 2025 the average RPG programmer will be 70 years old,”per one source, ASNA. In Fortra’s 2026 IBM i Marketplace Survey, a shortage of IBM i skills displaced cybersecurity as the industry’s top concern for the first time in nine years, cited by most of the 320 respondents.

The IBM Institute for Business Value, in 2023 research on application modernization across industries, found that 83% of executives called modernizing applications and data central to their strategy, while only 27% said they had actually modernized many of the necessary systems. For many companies, future-proofing these applications has become a central part of digital transformation.

A cottage industry exists to perform RPG modernization. For instance, Fresche Solutions builds X-Analysis, a tool that maps how old programs fit together and extracts their buried business rules. Profound Logic focuses on web-enabling RPG and on automated code transformation to Node.js, while LANSA, acquired by Idera in 2019 (according to IT Jungle), offers low-code tools for building new applications that coexist with RPG. IBM also supplies its own developer tools, including a popular open-source extension, Code for IBM i, that turns the widely used VS Code editor into an RPG workbench through an extension.

As with all things coding, AI-powered tools are playing an increasingly important role. As recently as early 2024, AI models had struggled to read RPG, because the proprietary language is scarce in their training data (unlike the more common COBOL, as IT Jungle explains). But by late 2025 that had changed. IBM responded with Project Bob, first introduced as watsonx Code Assistant for i and later remade as a fully-fledged agentic coding platform. Bob can explain, convert and test RPG and other languages, including the automated testing of converted code. Eighty thousand of IBM’s employees have used Bob, with surveyed users reporting it has raised their productivity by 45%.