Fourth-generation programming language

A *fourth-generation programming language* (abbreviated *4GL*) is a descriptive term used for programming languages and environments designed with a specific purpose in mind, such as the development of commercial business software. In the evolution of computing, the 4GL followed the 3GL in an upward trend
toward higher abstraction and statement power. The 4GL was followed by efforts to define and use a 5GL. The natural-language, block-structured mode of the third-generation programming languages improved the process of software development. However, 3GL development methods can be slow and error prone. It became clear that some applications could be developed more rapidly by adding a higher-level programming language and methodology which would generate the equivalent of very complicated 3GL instructions with fewer errors. In some senses, software engineering arose to handle 3GL development. 4GL and 5GL projects are more oriented toward problem solving and systems engineering.

All 4GLs are designed to reduce programming effort, the time it takes to develop software, and the cost of software development. They are not always successful in this task, sometimes resulting in inelegant and unmaintainable code. However, given the right problem, the use of an appropriate 4GL can be spectacularly successful as was seen with MARK-IV. The usability improvements obtained by some 4GLs (and their environment) allowed better exploration for heuristic solutions than did the 3GL.

Fourth-generation languages have often been compared to domain-specific programming languages(DSLs). Some researchers state that 4GLs are a sub-set of DSLs.Given the persistence of assembly language even now in advanced development environments (MS Studio), one expects that a system ought to be a mixture of all the generations, with only very limited use of the first.