The first part of this paper provides rigorous definitions for several basic concepts underlying the design of dependable programs, such as specification, program semantics, exception, program correctness, robustness, failure, fault, and error. The second part investigates what it means to handle exceptions in modular programs structured as hierarchies of data abstractions. The problems to be solved at each abstraction level, such as exception detection and propagation, consistent state recovery and masking are examined in detail. Both programmed exception handling and default exception handling (such as embodied for example in recovery blocks or database transactions) are considered. An assessment of the adequacy of backward recovery in providing tolerance of software design faults is made. An earlier version of this paper was published in "Dependability of Resilient Computers", T. Anderson, Editor, BSP Professional Books, Blackwell Scientific Publications, UK, 1989, pp. 68-97 INTRO...

. Automatic garbage collection relieves programmers from the burden of managing memory themselves and several techniques have been developed that make garbage collection feasible in many situations, including real time applications or within traditional programming languages. However optimal performance cannot always be achieved by a uniform general purpose solution. Sometimes an algorithm exhibits a predictable pattern of memory usage that could be better handled specifically, delaying as much as possible the intervention of the general purpose collector. This leads to the requirement for algorithm specific customisation of the collector strategies. We present a dynamic memory management framework which can be customised to the needs of an algorithm, while preserving the convenience of automatic collection in the normal case. The Customisable Memory Management (CMM) organizes memory in multiple heaps. Each heap is defined as a C++ class which encapsulates a particular storage discipli...

Parametric polymorphism or generic programming has been supported by a number of programming languages. Templates and generic parameters are most commonly used. When instantiated, templates and generic units generate new functions, types, packages or modules. This paper shows a different approach to parametric polymorphism in the frame of a new programming language called SIMPL. Polymorphic functions in SIMPL carry two lists of parameters: the hidden parameters and the formal parameters. The hidden parameters, which are used to parameterize a function, appear in the types of the formal function parameters, the result type, and in the body of a function. Hidden parameters are never passed explicitly when a function is called, but rather inferred implicitly by the type system. With hidden parameters, polymorphic functions can have a unique and efficient translation as will be shown in this paper. Keywords: Parameterized types, polymorphic functions, hidden parameters, SIMPL. 1 Introduc...