A Pascal extension for formal specificATion of computer networkprotocols. Protocols are described by modules which are communicATing NFAs. Modules are arranged in a dynamic hierarchy and communicATe AT named interaction points. EstPC Compiles Estelle into C. petdingo TranslATes Estelle into C++ Adopted by ITU-T. ISO 9074 (1989). ["The Formal Description Technique Estelle", M. Diaz et al eds, N-H 1989].