eCos is an open source, royalty-free, real-time operating system intended for embedded applications. The highly configurable nature of eCos allows the operating system to be customized to precise application requirements, delivering the best possible run-time performance and an optimized hardware resource footprint. A thriving net community has grown up around the operating system ensuring ongoing technical innovation and wide platform support. This tutorial gives a broad overview of the things that an engineer will need to know and do to evaluate eCos and develop applications. We will cover the following areas: an overview of the functionality of eCos, how to configure eCos, and how to write and build applications.