Cooper's dynamically installable control facility, which became famous as the “VBX” interface, was a well-known component of "Ruby". This innovation allowed any 3rd party developer to write a widget (control) as a DLL, put it in the Visual Basic directory, and Visual Basic would find it, communicate with it, and present it to the user as a seamless part of the program. The widget would appear in the tool palette and appropriate menus, and users could incorporate it into their Visual Basic applications. The invention of the “VBX” interface created an entire new marketplace for vendors of these “dynamically installable controls.” As a result of Cooper's work, many new software companies were able to deliver Windows software to market in the 1990s.