It includes embeded SQL, a report writer language, a form language mixed with imperative capabilities (like functions, if and while statements, etc).
This language is still widely used to develop business aplications, and is now property of IBM.
In the meanwhile several companies have built clone versions of 4GL, some with extended functionalities, like GUI(s) and IDE(s), namely 4JS and Querix.
A company in the Latin America built a convertor to java.
There is an free GPL version called Aubit 4GL.