fourth-generation language

fourth-generation language (4GL)

Fourth-generation computer programming language. 4GLs are closer to human language than other high-level languages and are accessible to people without formal training as programmers. They allow multiple common operations to be performed with a single programmer-entered command. They are intended to be easier for users than machine languages (first-generation), assembly languages (second-generation), and older high-level languages (third-generation).

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Also known as a 4GL, it is a computer language that is more advanced than traditional high-level programming languages. For example, in dBASE, the command List displays all the records in a data file. In second- and third-generation languages, instructions would have to be written to read each record, test for end of file, place each item of data on screen and go back and repeat the operation until there are no more records to process.

First-generation languages are machine languages; second-generation are machine dependent assembly languages; third-generation are high-level programming languages, such as FORTRAN, COBOL, BASIC, Pascal, and C.

Although many languages are called fourth-generation languages, they are actually a mix of third and fourth. For example, the List command in dBASE is a fourth-generation command, but applications programmed in dBASE are third-generation. The following command examples show the difference between third and fourth-generation syntax to open a customer file and display all names and addresses on screen.

    dBASE 3GL                dBASE 4GL
    use customer             use customer
    do while .not. eof()     list name, address
      ? name, address
      skip
    enddo

Query language and report writers are also fourth-generation languages. Any computer language with English-like commands that does not require traditional input-process-output logic falls into this category.

Many fourth-generation language functions are also built into graphical interfaces and activated by clicking and dragging. The commands are embedded into menus and buttons that are selected in an appropriate sequence.