The Sue/11 Operating System*
Ira Greenblatt, Richard C. Holt · INFOR Information Systems and Operational Research · 1976
The SUE/11 operating system is a small, special purpose operating system for the Digital Equipment Corporation PDP-11 minicomputer; it is presently being used to run SP/k, a studentoriented subset of PL/1. The system is written entirely in a high-level language, the SUE System Language. It is one of the first production systems to be based on monitors, a recently defined mechanism for handling process synchronization. The system is structured as the following layers of software: (1) the input-output interrupt handlers, (2) the kernel, which supports monitor operations, (3) the monitors, which control access to critical data such as inputoutput buffers, (4) the input-output processes, which provide buffering, (5) the file system, (6) the loader/overlayer, and (7) the Sp/k processor. Performance analysis indicates that very little CPU time is used by the operating system. The system is interesting as an example of production software based on these modern structuring mechanisms: high-level implementation language, monitors, and layers of virtual machines.