Report Program Generator, a programming language for business applications, was developed by IBM during the 1960's. Although IBM introduced RPG during an era of other commonly used programming languages such as Fortran, Cobol and Assembler, RPG gained wide acceptance as a quick and easy method of writing programs for a variety of business applications. As a result, RPG gained popularity on small-scale computer systems and quickly stepped into medium and large-scale installations. Evolving with IBM's various midrange and mainframe computer systems, the RPG programming language has progressed from RPG to RPG II, to RPG III, to RPG IV, to RPG ILE and now RPG Free. Much of the success and quick acceptance of RPG is because of its ability to handle some specific "housekeeping" chores that other languages only perform manually. The "inner clock" in the RPG Cycle addresses areas such as opening files, clearing and loading successive field values, turning indicators on and off, as well as following a program's logical progression from input to output. IBM has continually enhanced the RPG programming language, providing new operations that simplify the code and greater flexibility to control integration across platforms. The latest ILE version, Integrated Language Environment, presents RPG in the most structured, modular format ever, allowing programs to "branch out" to external routines of various languages, yet still perform as if they were one. Again, IBM has further enhanced the code by providing built-in functions (BIFs) and breaking away from fixed format specifications with RPG Free.
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