This paper presents a functional modeling application, FunctionCAD, based on integrated functional and process modeling within the Function Design Framework. FunctionCAD provides for mixed, hierarchical models of environment, process and function with relationships represented via flows of material, energy and signal. This paper discusses the technical details of the FunctionCAD software including its two major components: (1) the library, libFCAD, for handling the internal representation of the model and (2) the GUI for user-based model manipulation and visualization. The application of FunctionCAD within a computational, function-based conceptual design process is discussed along with the plugin manager and interface that have been developed as a part of the FunctionCAD software to allow interconnectivity with existing conceptual design tools. And finally, a detailed description of model creation within the FunctionCAD environment is provided to illustrate software operability.