The kernel of an operating system (OS) is its heart, and a great place to understand the fundamental issues of hardware, software, and their interface. The challenge is to be able to study a system that is sufficiently capable to be functional and practical, but still simple and clear enough to be understandable.

The C/OS is a great example of such a system. In addition to having this educational value, it is widely used and freely available, and has been used in a variety of other systems and applications. C/OS has a very interesting history, and the fact that it was actually developed as a basis for a product is reflected in the pragmatic nature of the book.

The early sections of the book give a simple overview of the elements of a real-time (RT) operating system, and then the structure of the C/OS kernel is presented. Examples are given that show the power of the system, as well as the low-level machine control details necessary for programming in such a system.

The following sections describe in more detail how to use the kernel methods to accomplish the basis tasks of system management. The majority of this is done through small examples demonstrating each capability, and line-by-line narratives of the code to do it. A few chapters then describe the porting of the kernel to other systems, with specifics for common 80x86 hardware. The remainder of the book (200 pages) is a reference manual, with the code interface specifications for each kernel service.

For teaching or self-learning, this is a simpler kernel than any current Linux kernel, which may be of value, particularly if one is interested in real-time properties. Otherwise, I think the main value of this book is for developers who want to understand and use a full-featured real-time OS kernel as a part of their product. It is a well-described and complete system.