Abstract: A concurrent programming system for constructing hard-real-time applications is described. The system is based on a novel semantics of inter-process communication called the real- time producer/consumer (RTP/C) paradigm. Process interactions are modeled as producer/consumer systems with a timing constraint on the rate at which the consumer must service the producer. The RTP/C paradigm provides a framework both for expressing processor-time-dependent computations and for reasoning about the real-time behavior of programs. A formal model of processor and resource allocation is used to determine necessary and sufficient conditions for realizing the RTP/C semantics of a program. The design of an interactive graphics system illustrates the use of the system.