An obsolete architecture in which everything (processes, files, I/O operations, etc.) is represented as an object. Objects are data structures in memory that may be manipulated by the total system (hardware and software); they provide a high-level description that allows for a high-level user interface. Objects have descriptors that are referred to variously as names, pointers, and labels. These descriptors also provide information as to the type of object and a description of capabilities that apply to the particular object. Object-oriented architecture systems could thus be considered as an extension or generalization of capability architecture systems, and had the same ability to provide a basis for protection and computer security.

Examples of object-oriented architecture systems were the IBM System 38, the Carnegie-Mellon experimental C.mmp/Hydra, and the Intel iAPX 432.