(4GL, or "report generator language") An "application specific" language, one with built-in knowledge of an application domain, in the way that SQL has built-in knowledge of the relational database domain.
The term was invented by Jim Martin to refer to non-procedural high level languages built around database systems.
Fourth generation languages are close to natural language and were built with the concept that certain applications could be generalised by adding limited programming ability to them.
When given a description of the data format and the report to generate, a 4GL system produces COBOL (or other 3GL) code, that actually reads and processes the data and formats the results.
Some examples of 4GL are: database query language e.g.SQL; Focus, Metafont, PostScript, S, IDL-PV, WAVE, Gauss, Mathematica, and data-stream languages such as AVS, APE, Iris Explorer.