In this thesis, we present the rapid prototyping technique in the functional Specification and Description Language (SDL) environment. We adopted the automation based paradigm proposed by the DoD, as the new discipline of software engineering to cope with the software crisis in developing the switching software, and used the User Software Engineering (USE) methodology to get the executable specification from the SDL representation. The executable specification is just the prototype. The validation and the maintenance of the software can be performed in the requirement analysis phase of the life cycle.