This paper is the second in a three-part series on SYS IV, an instructional management system developed by the PLATO Curriculum Project (PCP) that incorporates some of the features of the previous SYS systems. Focus is primarily on the new features that make the system unique. Following a brief background section explaining the purpose of SYS IV, primarily technical issues are addressed. Specific features described are the SYS IV files and files structures, which include the system catalog file, the subfiles files, and system files list. The programing language Instructor Logic (IL), whose specific purpose is to provide a curriculum designer with flexibility in curriculum structure, is explained, and all IL commands are listed with a brief description of their use and purpose. Additional functions described are the router, group editor, catalog editor, implementation scan utility, and the testing package. Final comments address the future of SYS IV. An appendix provides a sample of an IL program from the PCP Reading Comprehension material. (LMM)