This programmer's guide/reference manual provides documentation and support for the ParcPlace Systems C++ based tool kit that enables users to write programs which operate under X Window and Motif. Tutorial in approach, it teaches readers how to program using the Object Interface (OI) library. Contents apply to any implementation of OI, regardless of hardware or supporting software. Chs. 1-6 provide introductory, tutorial information on the major features of programming using OI (the structure and relationships involved); how to compile, link, and execute an OI application; and on OI naming conventions, constants and types, and initialization, termination, and other independent functions. Chs. 6-37 discuss each class of objects which can be displayed on the screen—presented in order from the simplest to the most complex. Chs. 38-43 consider the OI connection to the X server; show how to use the OI resource and translation mechanisms; and explain how to derive customized OI subclasses. Includes OI examples ranging from simple ones intended only to show how to get an object on the screen, to those that, if expanded, could be useful programs.