Experiences with the portability of concurrent PASCAL

Abstract

SUlMlMARYThe process of transporting Brinch Hansen's implementation of Concurrent PASCAL to another minicomputer is described. Applicable porting strategies are discussed with emphasis on the design decisions made for a specific transportation. Important design decisions include the use of a virtual code interpreter and implementation in an operating system environment. The problems of this transportation are illustrated with accompanying suggestions for a more portable system. KEY WORDS Portability Concurrent PASCAL Kernel Interpreters MultiprogrammingOperating systems Abstract machine Address mapping computers. Per Brinch Hansen, the designer of Concurrent PASCAL, and his staff at California Institute of Technology have implemented Concurrent PASCAL on the DEC PDP-1 1.2 This implementation has been widely distributed both in a version suitable for the PDP-11 and in a version intended to be moved to other computers. The language implementation includes a compiler for Concurrent PASCAL and a compiler for Sequential PASCAL, a subset of Standard PASCAL as defined by Wirth,3 which are both written in Sequential PASCAL. The Brinch Hansen distribution system also includes an operating system (SOLO)4 which is written in Concurrent PASCAL and provides a single-user environment for the development of both Sequential and Concurrent PASCAL programs. This paper contains a summary of the porting strategy used and the experiences and insight gained during the process of moving the Brinch Hansen system to an Interdata 8/32 computer. APPROACH T O PORTABILITYSeveral techniques have been proposed or used in moving programs and/or programming systems from one computer to another.6 Among these techniques are 'standard' languages, macro implementations and abstract machine architectures. With regard to the Brinch Hansen system, two of these approaches are immediately applicable. Similar to the

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