This paper discusses the response time problem for concurrent processes sharing resources which are granted according to an FCFS strategy. The problem is shown to be NP-hard, but when less than four resources are shared, a restricted case is shown to be solvable in linear time.

In this paper we propose a new model for real-time programs. In the model a set of concurrent processes executed by a time-shared single processor interacts with a set of input tapes and a set of output tapes representing their environment. Processes access their tapes through reading heads and writing heads. The distinctive feature of our model is the way the movement of heads is controlled. Their movement is not controlled by programs. Instead, they move unidirectionally scanning the tapes according to the flow of time. Stimuli for a process (responses by a process) are modeled as a sequence of symbols, representing data, interspersed with sequences of the special symbol representing time intervals separating successive stimuli (responses). Next, for the model, we define important properties of real-time programs including data overrun, deadlock and correctness, and show an example of verification of these properties for a small and typical real-time program.