All versions of RPG.
RPG is a high-level programming language (HLL) for business applications. RPG is an IBM proprietary programming language and its later versions are available only on IBM i- or OS/400-based systems.
It has a long history, having been developed by IBM in 1959 as the Report Program Generator — a tool to replicate punched card processing on the IBM 1401 — then updated to RPG II for the IBM System/3 in the late 1960s, and since evolved into an HLL equivalent to COBOL and PL/I.
It remains a popular programming language on the IBM i operating system, which runs on IBM Power platform hardware. The current version, RPG IV, a.k.a. ILE RPG, provides a modern programming environment. Wikipedia
Early versions of RPG used directives to access and update the files. This approach required a developer to identify the specific path to the data, resulting in constraints on portability. This method is still supported today.
But when the concept of a database was introduced to the platform, so was SQL, the industry-wide method for database access. The SQL precompiler now allows RPG developers to embed standard SQL statements directly into a program. At runtime, the SQL is translated into a request to the database and the database manager serves up the result.
Incidently, most of the programs written more than 30 years ago will still run on today's machines.
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