Combining Oberon with active objects

Abstract

Multitasking is a topic on which many discussions have been held. There are different opinions about its need. Our own operating system, Oberon, was originally designed as a single user and single process system. While developing server systems and simulation kits we came to the conclusion that we need some notion of slim and easy to use process. We then decided to start a new project comprising the design of a new kernel and a new compiler for the support of concurrent execution of several processes on different priority levels with an appropriate protection mechanism preventing processes from inadmissible access to each other. The idea of active objects, simultaneously representing processes and containing both their action and their data, was the base for the ‘Active-Oberon’ project. Active objects are independent processes scheduled by the system. The management of the memory including stack allocation devolves on the new kernel. This takes much responsibility away from the programmer and makes the system safer.

The goal of this paper is to present the implementation of the ‘Active-Oberon’ project whose concepts are described in detail in [Gut96b].