eXpOS is basically built upon the XSM architecture. Architecture includes the specifications for the machine organisation, paging and interrupt handling and also provides the machine level instruction set.
eXpOS is a tiny multiprogramming operating system. It has a very simple specification that allows a junior undergraduate computer science student to implement it in a few months.
To implement the eXpOS certain tools are provided along with the package. This includes SPL and ExpL compilers, XSM simulator and a UNIX-XFS Interface called XFS interface.
The inteface between the application programs and the OS requires the specification of system call intefaces, format of executables, the virtual instruction set, the virtual memory layout and configuration.
The roadmap guides you step by step towards the complete implementation of the operating system. Concepts needed for completing each step will be introduced at the appropriate point.