Between 1999 and 2006, Topsy was actively used for teaching and in a hands-on laboratory in the second year undergraduate course Technische Informatik II at the department of Information Technology and Electrical Engineering of ETH Zurich.
Topsy is a small (~20k machine code) multi-threaded microkernel. It is written in ANSI C and protects kernel threads from user programs. It supports memory management, thread/process control and an IO and driver subsystem. Communication and sychronization is implemented with messages.
Who should learn more about Topsy?
Topsy was written for an EE undergraduate course which focuses on concurrency, device programming and OS concepts. It should also fit more advanced CS courses in operating systems.
Although we did the best to reuse software components and to program as clearly as possible you should be fluent in C to read Topsy source.
See the Topsy OS running inside your web browser!
Right, you can see Topsy running on the web! Any Java enabled browser can run a MIPS R3000 simulator that loads a demo kernel over the Internet. Click here for the demo.
Interesting OS Links
Many OS's with short description and classification: Francois-Rene Rideau's OS homepage
Java Tools for OS Courses: Max Hailperin's Java in Operating Systems Courses
The operating system developers homepage