资料来源 : Free On-Line Dictionary of Computing

fourth generation language
     
         (4GL) An "application specific" language, one with
        built-in knowledge of an application domain, in the way that
        {SQL} has built-in knowledge of the database domain.  Pure
        4GLs do not contain conditionals (if-then-else) and loops
        (for, while, do), though some languages are combinations of
        {third generation languages} and 4GLs.
     
        The term was invented by Jim Martin to refer to
        {non-procedural} {high level languages} built around
        {database} systems.  The first three generations were
        developed fairly quickly, but it was still frustrating, slow,
        and error prone to program computers, leading to the first
        "programming crisis", in which the amount of work that might
        be assigned to programmers greatly exceeded the amount of
        programmer time available to do it.  Meanwhile, a lot of
        experience was gathered in certain areas, and it became clear
        that certain applications could be generalised by adding
        limited programming languages to them.  Thus were born {report
        generator} languages, which were fed a description of the data
        format and the report to generate and turned that into a
        {COBOL} (or other language) program which actually contained
        the commands to read and process the data and place the
        results on the page.
     
        Some other successful 4th-generation languages are: {database
        query languages}, e.g. {SQL}; {Focus}, {Metafont},
        {PostScript}, {RPG-II}, {S}, {IDL-PV/WAVE}, {Gauss},
        {Mathematica}; and {data-stream languages} such as {AVS},
        {APE}, {Iris Explorer}.
     
        (2003-07-29)