Publisher Summary To begin a system-level design, a clear understanding of what the final software design must accomplish is essential. The source of this information is the system requirements document, which contains the required functions, timing, communications needs, and priorities. If the requirements document does not contain these answers, it is up to the designer to obtain this information. The answer may come through asking questions of the department that generated the document, such as Marketing. This chapter explains the actual software design process. This chapter uses a top-down approach to design and deals primarily with the top level of the design. This level of design is referred to as the system level. At this level, the general organization of the software will be developed, including definition of the tasks, layout of the communications, determination of the overall system timing, and the high-level definition of the priority structure.