BACKGROUND: We aim to provide a conceptual view of the origins, development and future directions of FACTOR, a popular free program for fitting the factor analysis (FA) model. METHOD: The study is organized into three parts. In the first part we discuss FACTOR in its initial period (2006-2012) as a traditional FA program with many new and cutting-edge features. The second part discusses the present period (2013-2016) in which FACTOR has developed into a comprehensive program embedded in the framework of structural equation modelling and item response theory. The third part discusses expected future developments. RESULTS: at present FACTOR has attained a degree of technical development comparable to commercial software, and offers options not available elsewhere. DISCUSSION: We discuss several shortcomings as well as points that require changes or improvements. We also discuss the functioning of FACTOR within its community of users.
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