The Instruction Set Processor Specifications (ISPS) computer description language is an evolutionary step towards the formalization of the digital design process at the higher or behavioral levels. It has been used as a design tool, which covers a wider area of application than any other hardware description language. Thus, besides simulation and synthesis of hardware, software generation program verification, and architecture evaluation and control are among the current applications based on ISPS. The range of current and contemplated application areas are proof of the usefulness of the notation and its extension mechanisms. ISPS supports a wide range of applications, rather than a wide range of design levels. Thus, this paper is divided into two parts. The first part describes the notation, its intended use, and the extension mechanisms which allow multiple applications or areas of research to co-exit and share machine descriptions. The second part describes some of the current applications for ISPS.