standalone program:

This article, last of the original three done altogether in 1990, on getting the critical pieces functioning independantly that we needed to do the port. Once these we obtained, the kernel was inevitable.

We coded specialized trap handlers for interrupt traps, as these were initimate with the systems interrupt control hardware, not part of the processor.

We describe the need and use of a cross-support environment to create 386 code from a non-386 machine, so as to create the initial binarys before our port can generate them.

Portions of the root allow the kernel to be installed as the fundamental component of the operating system. These standalone programs occupy space within the root filesystem.

Nothing ever goes right the first time, so a incremental process of bringing up the filesystem, from standalone utilities to system initialization allows us to debug flaws in filesystem creation, often artifacts of its non-native creation.

Whats different about operating systems like Unix that use a root filesystem, and other systems that don't require a filesystem to be mounted initially to operate?