TUNIS (Toronto University System) was a Unix-like operating system, developed at the University of Toronto in the early 1980s. TUNIS was a portable operating system compatible with Unix V7, but with a completely redesigned kernel, written in Concurrent Euclid. Programs that ran under Unix V7 could be run under TUNIS with no modification.
TUNIS was designed for teaching, and was intended to provide a model for the design of well-structured, highly portable, easily understood Unix-like operating systems. It made extensive use of Concurrent Euclid modules to isolate machine dependencies and provide a clean internal structure through information hiding, and of Concurrent Euclid's built-in processes and synchronization features to make it easy to understand and maintain.
- R.C. Holt (1982) TUNIS: a Unix look-alike written in concurrent Euclid (abstract). ACM SIGOPS Operating Systems Review 16(1):4--5.