Computer software libraries are an essential element of a software configuration management (CM) system. However, the term, 'library' while commonly used in the world of software, has had no significance in the field of CM until recently. Further, even in the software, world, the term has several different meanings. The purpose of this bulletin is to relate the term to the software CM system, e. g., the role of a library in the release of software. It describes the three types of libraries which are involved in the system, it discusses the principles and factors which affect their design and it presents a model, including samples o records and forms. Also included is a 'univerals' position description for a librarian.