Shift  is a programming language for describing dynamic networks of hybrid automata. Such systems consist of components which can be created, interconnected and destroyed as the system evolves. Components exhibit hybrid behavior, consisting of continuous-time phases separated by discrete-event transitions. Components may evolve independently, or they may interact through their inputs, outputs and exported events. The interaction network itself may evolve.Tkshift is a Tcl/Tk program for controlling and illustrating the simulation.The Shift model offers the proper level of abstraction for describing complex applications such as automated highway systems, air traffic control systems, robotic shopfloors, coordinated submarines and other systems whose operation cannot be captured easily by conventional models.A compiler translates a Shift program to a C program, and the Shift run-time system produces an executable program. The executable program, when run, simulates the design specified in the Shift source program.