doni: The allocation structure is not what people need to understand. To demystify MicroOS, one needs to know what it does and why it was developed specifically for flash memory, which can't be re-written without first erasing existing data. Non-volatile memory like hard drives and floppies can be rewritten without first erasing. The NFFS was developed to address this specific issue with Flash memory.
I'll post a more extensive explanation when I have time.