An introduction to the Gypsy programminQ and specification language is given. Gypsy is a hiah-level programmina language with facilities for general pronramming and also for systems programming that is oriented toward communications processing.This includes facilities for concurrent processes and process synchronization. Gypsy also contains facilities for detecting and processing errors that are due to the actual running of the program in an imperfect environment. The specification facilities give a precise way of expressinn the desired properties of the Gypsy programs. All of the features of Gypsy are fully verifiable, either by formal proof or by validation at run time. An overview of the lanouaae desian and a detailed example program are given.
This paper defines a capability implementation which uses the memory management hardware and the TRAP instruction of the higher members of the Digital Equipment Corporation PDP-11/XX (XX = 34, 45, 55, 70) to create a capability architecture processor. No modifications to hardware are necessary. The architecture created has a strong similarity to that of the Plessey 250. An operating system based on this architecture could provide a basis for implementation of highly reliable and secure software systems on a common and inexpensive minicomputer.
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