This article describes a new approach to hardware-software codesign for complex embedded systems, using high-level programming languages, such as C, C++, Java, or Ada. Unlike previous approaches, we do not distribute parts of the behavior between the different subsystems. We map the entire behavior onto the whole system, and the partition is made implicitly during the synthesis process. We divide the system specification into behavior, architecture and design criteria, to maximize reuse opportunities and to increase the flexibility of the design environment.