Programming-Language Structures for Representing and Optimizing Operating-System Resources

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This research project seeks to demonstrate that fundamental operating system services and resources can and should be represented directly in the natural linguistic structures of advanced programming languages. A component of this effort is to develop aggressive optimisation strategies making this modelling practical and efficient. The central question underlying the research is: how can the benefits of advanced programming languages be brought to bear upon current systems-programming practice? Modern computer applications are most commonly written in C, a language well- known for its lack of support for writing modular, robust programs. C has no module system, allows dangerous "casting" of data types, violates abstraction barriers, provides no garbage- collection support for automatic storage management, has no concurrency operators, and generally exposes the details of the underlying machine to the programmer. It is not defined in terms of a mathematically sound underlying semantics. As a result, modern software is fragile, error-prone, and difficult to build, maintain or reuse. Modern programming languages, such as the ML family of languages, provide much more support to the programmer for writing large, robust programs. Unfortunately, these languages are not yet practical tools for implementing real-world systems software. In practice, programs written in these languages are slow, use large amounts of memory, and have awkward interfaces to OS services. Providing access from programs written in these languages to the machine resources, in ways that are natural to the language, should help to address these shortcomings. This research enables new optimisations and makes available new models to the programmer, allowing systems programs to be written that exploit the expressive power of advanced programming languages. A service kernel provides access to the underlying machine resources in a way that is tightly integrated, both in architecture and in implem entation, with advanced languages. The research issue is to investigate the architecture of an operating system that is symbiotic, not with C, but with a modern programming language, and to develop technologies for exploiting the tight integration of the OS and the compiler to provide efficient, high-level services. The kernel is being developed in ML, on two hardware platforms: a bare Intel PC system, and a wireless, mobile "personal digital assistant" with limited on-board resources. ***