Specifying the system

Abstract Software components of microprocessor systems now consume a major part of development costs. This has meant that there is a growing trend for software to be designed with a view to future extension, which places constraints on the structure of the design if any extension is to be achieved with a minimum of restructuring. Software validation — verifying each function of the system against performance requirements — is also becoming increasingly important. These requirements must be made explicit at the start of the design process. This article considers the requirements analysis techniques and design methodologies which should be applied to system design to allow the production of software that carries out the specified functions while being amenable to future extension without completely redesigning the system.