We can't even go beyond the third generation. The first generation languages are all the native machine code languages. The second generation languages are the low-level symbolic languages such as assembly language. The third generation languages are all the high-level symbolic languages, such as C, C++, Java, Pascal, Cobol and so on. There are no fourth generation languages.
The term "fourth generation" was first used by marketing types to make their third generation languages seem superior to other third generation languages, regardless of what features they actually provided. While there have been several attempts to re-classify third-generation languages, there is no standardised convention and thus no way to compare languages objectively by generation alone. Languages are best classified by the paradigms they support (procedural, structured, object-oriented, functional, logical and so on) and/or the domains they operate within (general purpose programming, Artificial Intelligence programming, and so on).
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