 He documented the system in his 1975 book "Principles of Program Design".In a 2001 conference talk, he provided a retrospective analysis of the original driving forces behind the method, and related it to subsequent software engineering developments.Jackson's aim was to make COBOL batch file processing programs easier to modify and maintain, but the method can be used to design programs for any programming language that has structured control constructs, languages such as C, Java and Perl.