Xous is a microkernel operating system with processes, threads, and messages. It is designed to have an extremely small kernel that delegates as much as possible to userspace. This book describes the operating system kernel as well as the services that support normal operating system behavior.

As this book is a work in progress, some chapters are placeholders and will appear blank.

The book is written for two audiences: kernel maintainers, and application developers.

• Chapters 2 (Server Architecture),

  • 3 (Introducing the Kernel), and
  • 5 (System Startup) are primarily for kernel maintainers and system programmers.

• Chapters 1 (Getting Started),

  • 4 (Renode Emulation),
  • 6 (Build System Overview),
  • 7 (Messages) and
  • 8 (Graphics) are more appropriate for application developers.

• Chapter 9 (PDDB) covers the Plausibly Deniable DataBase, and has sub-sections for both kernel and application developers.

ist of open source real-time operating systems

NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are Posix and ANSI standards. Additional standard APIs from Unix and other common RTOS's (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).

NuttX was first released in 2007 by Gregory Nutt under the permissive BSD license.