Unix system calls to create and execute processes are usually hard to understand for novice students. Using graphics for visualizing the behaviour of these system calls can be useful both for the teacher to explain and for the students to understand them. The problem here is that there is no software specifically addressed to generate graphical representations of these kind of programs, and to develop it would be costly. Instead of developing a complete system to visualize programs that use Unix system calls, we turned to a "cheaper" alternative solution. In this paper we show how we have used the open source graphviz tool to develop a simple way of generating graphical representations of the behaviour of these system calls, thus facilitating the comprehension of this important part in the learning of the Unix operating system.
This paper describes the application of the Formal Description Technique ESTEILE to the modelling and design of Operating Systems. We describe the overall scheme of a multiprogramming operating system and then we design in a top-down way the operating system, proposing its specification in ESTELLE at the same time.The use of ESTELLE allows not only the formal specification of an operating system like the one we describe, but also its simulation, and even its implementation, using development tools like the WorkStation EWS (developed in the Esprit project 1265: Sedos Estelle Demonstrator).Ali of the above makes the known advantages of the usual application of Formal Description Techniques to Communication Protocols available to the modelling, formalization and design of other kind of systems, such as Operating Systems. D. Hogrefe et al. (eds.
Synchronous Estelle is a new language designed to specify distributed reactive systems. We have developed this new language, that tries to merge both asynchronous and synchronous paradigms, as an answer to some problems not solved with existing techniques. We will show its syntactic and semantic features, the way to obtain executable programs according to a specification, and some hints to perform the validation of the programs written in this language. The Steam Boiler Control Problem, a referent study case in the field of reactive systems, has been used to study the applicability of Synchronous Estelle to distributed reactive systems.
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