In 1975, Academician Glushkov proposed the concept of conveyor production of software from ready-made programs. This paper presents new theoretical results and analyzes the development of this concept on the basis of examples of earlier and current software factories. This makes it possible to testify to fact of emergence of the following two basic production concepts: interface as a stub in transmitting and transforming given software and as an integrated environment for assembling various ready-made products in some programming languages. Over the years, they were constantly being improved and become the basis for a modern software factory including an assembly infrastructure with the use of human, technological, and tool resources for assembling ready-made programs. Within the framework of a system, new interface tools will be developed for heterogeneous programs to convert standard data types to those available in many programming languages.