Beyond concurrent Pascal

Abstract

We take the view that operating systems should not be written in assembly language. Alternatives are machine oriented high-level languages and “safe” languages in the style of Concurrent Pascal and MODULA. A serious drawback of the Concurrent Pascal approach is the fact that those very language features that pertain to operating systems must be implemented separately, using some other language. A technique is presented which solves this problem. This technique is based on user-defined trap handling. It is exhibited by demonstrating how virtual memory systems can be constructed using Concurrent Pascal and how process management can be moved from the kernel to the Concurrent Pascal program. We demonstrate that a fundamental solution of the difficulties with Concurrent Pascal, MODULA, and similar languages cannot be found in going back to classical implementation languages, but in designing languages that are not rich with special features, but powerful with respect to extension and shrinkage.