RPGLE is a high-level programming language (HLL) for business applications for programs running in the Integrated Language Environment (ILE). IBM is the creator of RPGLE. Use this tag for all questions about RPG IV and free format RPG. Use the RPG tag for questions about older versions of RPG and non-IBM variants of the language.
The latest version of RPG is RPG IV (aka ILE RPG) on IBM's Power i servers; it inherits the System i Integrated Language Environment’s features such as prototyped functions and procedures, static and dynamic binding, access to C routine libraries, dynamic link libraries, and fully recursive and re-entrant modular code.
RPG (also called RPG IV and RPGLE) is a popular programming language of the IBM Power i platform. Originally created as a report writer tool to replicate card processing on the IBM System/3 in the early 1960s, RPG has since evolved into an HLL equivalent to COBOL and PL/I.
An RPG program typically starts off with File Specifications, listing all files being written to, read from or updated, followed by Data Definition Specifications containing program elements such as Data Structures and dimensional arrays, much like a "Working-Storage" section of a COBOL program or var statements in a Pascal program. This is followed by Calculation Specifications, which contain the actual meat of the code. Output Specifications can follow which can be used to determine the layout of other files or reports. Alternatively files, some data structures and reports can be defined externally, mostly eliminating the need to hand code input and output specifications.
In the early days of RPG, its major strength was known as the program cycle: every RPG program executes within an implied loop, which can apply the program to every record of a file. At that time each record (individual punched card) would be compared to each line in the program, which would act upon the record, or not, based upon whether that line had an "indicator" turned "on" or "off" — from a set of logical variables numbered 01–99 for user-defined purposes, or other smaller sets based upon record, field, or report processing functions.
Alternatively, the cycle can make an interactive program continue to run until explicitly stopped.
Today, most RPG programmers avoid using the cycle in favor of controlling the flow of the program with standard looping constructs. The concept of level breaks and matching records is unique to the RPG language. It was originally developed with card readers in mind.
