Chapter 15

Using examples, explain why real-time systems usually have to be implemented using concurrent processes.

Explain why an object-oriented approach to software development may not be suitable for real-time systems.

Draw state machine models of the control software for the following systems: An automatic washing machine that has different programs for different types of clothes. The software for a compact disk player. A telephone answering machine that records incoming messages and displays the number of accepted messages on an LED display. The system should allow the telephone owner to dial in, type a sequence of numbers (identified as tones) and have the recorded messages replayed over the phone. A vending machine that can dispense coffee with and without milk and sugar. The user deposits a coin and makes his or her selection by pressing a button on the machine. This causes a cup with powdered coffee to be output. The user places this cup under a tap, presses another button and hot water is dispensed.

Design a process architecture for an environmental monitoring system that collects data from a set of air quality sensors situated around a city. There are 5000 sensors organised into 100 neighbourhoods. Each sensor must be interrogated four times per second. When more than 30% of the sensors in a particular neighbourhood indicate that the air quality is below an acceptable level, local warning lights are activated. All sensors return the readings to a central computer, which generates reports every 15 minutes on the air quality in the city.

Discuss the strengths and weaknesses of Java as a programming language for real-time systems. To what extent will the problems of real-time programming on Java disappear when faster processors are used?

You are asked to work on a real-time development project for a military application but have no previous experience of projects in that domain. Discuss what you, as a professional software engineer, should do before starting work on the project.