Testing Provably correct. Guaranteed to be flawless. Storage Allocation Write anywhere paging. Allocation becomes trivial. Software structure Implemented as a set of sequential processes.
Process abstracts out timing information.
One process per user program. One process per peripheral device. Use semaphores to synchronize across processes, thereby guaranteeing that there are no misunderstood interactions. FS uses MM for buffering. Eliminating such circularities will make system easier to build and maintain.