Abstract: A telecommunication and development system for the switching of voice and data under computer control in a customer programmable environment that allows real-time modification of communication services. The computer program controlling the system is written in a nonprocedural language that allows for the direct control of the telecommunication system on the basis of state definition, event definition, and action definition. Program scripts define a particular feature, and each script consists of a plurality of triples that automatically respond to the system state and signal information to execute the necessary actions to provide part of a feature to the telecommunication system. During provision of telecommunication services, a customer can add new features that not only add new operations to the system, but modify existing operations without interfering with the present operation of the system.