Converged communication and radar sensing systems have attained increasing at-tention in recent years. The development of converged radar-data systems is reviewed, with a special focus on millimeter/terahertz systems as a promising trend. Firstly, we present histori-cal development and convergence technology concept for communication-radar systems, and highlight some emerging technologies in this area. We then provide an updated and compre-hensive survey of several converged systems operating in different microwave and millimeter frequency bands, by providing some selective typical communication and radar sensing sys-tems. In this part, we also summarize and compare the system performance in terms of maxi-mum range/range resolution for radar mode and Bit Error Rate (BER)/wireless distance for communication mode. In the last section, the convergence of millimeter/terahertz communica-tion-radar system is concluded by analyzing the prospect of millimeter-wave/terahertz tech-nologies in providing ultrafast data rates and high resolution for our smart future.