In recent years, increases in complexity of hardware/firmware systems, and the concern for systems reliability have resulted in growing interest in methodologies and tools for the design, description and verification of computer systems. A vital component of any such design methodology is the language used for representing the design. In the case of particularly complex systems the design process may involve a succession of stages each of which represents the system at a particular level of abstraction. In such situations several languages may be required, each suited to a particular level of abstraction. We present here, one such family of languages , consisting at present of two members, S*A, an architectural description language, and S*, a high level microprogramming language schema. These closely related (“kin”) languages may be used collaboratively for the systematic, top-down development of an architecture, down to the microcode level. The resulting descriptions of the architecture provide, in addition, a complete unified document of the multilevel design process.