Program code compression is an emerging research activity that is having an impact in several production areas such as networking and embedded systems. This is because the reduced-sized code can have a positive impact on network traffic and embedded system costs such as memory requirements and power consumption. Although code-size reduction is a relatively new research area, numerous publications already exist on it. The methods published usually have different motivations and a variety of application contexts. They may use different principles and their publications often use diverse notations. To our knowledge, there are no publications that present a good overview of this broad range of methods and give a useful assessment. This article surveys twelve methods and several related works appearing in some 50 papers published up to now. We provide extensive assessment criteria for evaluating the methods and offer a basis for comparison. We conclude that it is fairly hard to make any fair comparisons of the methods or draw conclusions about their applicability.

This article presents a user-fn'endly f o m l method for obtaining comprehensive feedback from the behaviour of a design of a distributed system. The method consists of abstracting and reducing the behaviour and showing the result in a graphical form on a computer screen. Deadlocks, livelocks, incorrect actions and many other kinds of design errors can often be easily discovered from the graphical representation. The method differs from animation, simulation and testing in that it analyses all possible behaviours simultaneously. For instance, i f the graphical representation does not contain a deadlock, then the system is guaranteed to be free from deadlocks. The method is illustrated by using it in the development of a wellknown communication protocol. This article concentrates on the use of the method; the underlying theory and computer tools have been discussed elsewhere.

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