This paper describes the design of a software development system for real-time controllers (or small embedded computers), which provides an advanced envimonment for developing and testing of software for a real-time controller. This system offers a concurrent language called *C and its development tool including a simulator for evaluating the execution time. *C is fundamentally based on the C language, and incorporates facilities for concurrency. The simulator intends to facilitate testing of a *C program to be executed on a real-time controller. The experimental system, which targets a single CPU real-time controller with a real-time monitor, is implemented on the UNIX operating system.